Acoustics 101 - SoundRite Audio Visual
Auralex® Acoustics, Inc.
Practical Guidelines
For Constructing Accurate
Acoustical Spaces
Including Advice On The Proper Materials To Use
Eric T. Smith
Edited by
Jeff D. Szymanski, PE
July 2004
Version 3.0
Published & © Copyright 1993, 2004 by Auralex® Acoustics, Inc.
6853 Hillsdale Court, Indianapolis IN USA 46250-2039 •
CHAPTER 1..........................................................................................................................................6
BASICS OF ACOUSTICS.................................................................................................................6
ACOUSTICAL DEFINITIONS ...........................................................................................................7
Acoustics 101 Definitions ...........................................................................................................7
GENERAL TECHNICAL INFORMATION .........................................................................................9
Absorption Coefficients and NRC ............................................................................................12
A final thought ...........................................................................................................................13
CHAPTER 2........................................................................................................................................14
MATERIALS AND PRODUCTS DISCUSSED................................................................................14
Common Construction Materials .............................................................................................14
Specialty Construction Materials .............................................................................................15
Auralex Products .......................................................................................................................16
CHAPTER 3........................................................................................................................................18
FLOORS .........................................................................................................................................18
Stringers .....................................................................................................................................21
CEILINGS .......................................................................................................................................22
(Non-)Flat Ceilings .....................................................................................................................23
Cathedral Ceiling Treatment for Live Rooms ..........................................................................24
Mr. T (Bar)...................................................................................................................................25
Existing Walls ............................................................................................................................26
Construction ..............................................................................................................................27
CHAPTER 4........................................................................................................................................29
DOORS ...........................................................................................................................................29
Isolation ......................................................................................................................................29
Garage doors .............................................................................................................................30
WINDOWS ......................................................................................................................................31
Exterior .......................................................................................................................................31
Interior ........................................................................................................................................31
HVAC (HEATING AND COOLING SYSTEMS) ..............................................................................33
The Air Handler ..........................................................................................................................33
The Fan .......................................................................................................................................34
Connections ...............................................................................................................................34
Terminations ..............................................................................................................................36
ELECTRICAL ISSUES....................................................................................................................36
CHAPTER 5........................................................................................................................................38
MONITOR MOUNTING SOLUTIONS .............................................................................................38
ROOM DESIGNS ............................................................................................................................38
Angled Surfaces ........................................................................................................................38
Room Dimensions .....................................................................................................................39
The Acoustics 101 Room ..........................................................................................................40
5.1 Mixing Rooms ......................................................................................................................40
Other Resources ........................................................................................................................41
APPLICATION EXAMPLES ...........................................................................................................41
General Resources ....................................................................................................................41
Night Club Isolation ...................................................................................................................41
Garage Isolation and Treatment ...............................................................................................42
MORE CONSTRUCTION TIPS.......................................................................................................43
PERSONALIZED ROOM ANALYSIS FORM..................................................................................44
APPENDIX 1.......................................................................................................................................45
Online Forums ...........................................................................................................................45
Professional Organizations ......................................................................................................45
Professional Design Assistance ..............................................................................................45
Acoustical Prediction, Test and Measurement .......................................................................45
Cool Corporate (non-Auralex) Stuff .........................................................................................45
Cool People ................................................................................................................................46
Other Cool Stuff .........................................................................................................................46
APPENDIX 2.......................................................................................................................................47
THE ACOUSTICS 101 ROOM ........................................................................................................47
Welcome to our newly expanded and revised Acoustics, the world’s best source for bottom
line, no BS, just-the-facts-ma’am advice on how to build a good sounding recording studio or listening
room. The tips contained in this small booklet have worked for me and have worked for others,
including many of our most famous clients. They will work for you and, if well implemented, should
actually exceed your sonic requirements and expectations without breaking your piggy bank. These
tips can save you a lot of time and grief!
What follows in Acoustics 101 is knowledge we’ve gained over our decades of experience in
broadcasting, music and acoustics - all condensed into one handy little reference guide and put into
language virtually anyone interested in controlling sound can understand. It doesn’t contain any hardto-decipher charts or graphs. There’s no smoke and mirrors, no dog and pony shows. Just good,
solid, cut-to-the-chase advice that you’d be hard pressed to find anywhere else — and certainly not
for free! We used to sell Acoustics 101, but are happy to be in a position now to provide it here for
you at no charge. As acoustical consultants, we often charge quite healthy sums to impart this sort of
knowledge, but feel free to read Acoustics 101 at your leisure....there’s certainly no "per diem" charge
like there’d be if we came out to consult you in person!
How confused you must be when you read so many conflicting opinions in the audio press about the
"right" way to control sound—or even how to form a "correct" opinion of your own about what
constitutes "desirable" sound. I feel your pain. All I can say is this: we at Auralex have decades of
experience in broadcast, studio design, live performance and recording and have never had a single
complaint about advice we’ve given. As the president of Auralex, I feel confident in saying that we
know what it takes to make good sound and what it takes to make a room sound good. Frankly, our
famous clients attest to our level of knowledge and the quality of our acoustical products. Collectively,
we’ve built, worked in and consulted enough facilities that we’ve got something quite valuable to offer
you; something my personal search long ago taught me simply isn’t available anywhere else. We
provide GREAT acoustical advice that doesn’t cost an arm and a leg and that us plain folks can
understand and put into practice all by ourselves.
One thing you’ll probably notice right away - Acoustics 101 is brief and to the point. No lab values, no
intense charts, no graphs. No 500 pages of tiny print for you to weed through just to find the answer
to some basic question... just real-world advice. So, if you’re a technohead who’s obsessed with
formulas and who believes computers and calibrated reference mic’s are absolutely necessary to
build a good-sounding room, you may not find in Acoustics 101 what you’re looking for. There are
plenty of books at your local library written in that high-brow style; I should know, I’ve read most of
them. If you have, too, and they got your head spinning and eyes rolling around like BBs like they did
mine, you’ve come to the right place. Acoustics 101 will give you just the sort of real world advice you
were hoping you’d find in all those other books, but without all the additional fluff and tough-to-follow
If you’ve not read all the other books out there, great! Acoustics 101 could save you hours and hours
of time and trouble because we’ve taken everything we’ve learned, thought up, observed and heard
about in all our years in broadcasting, recording and pro sound and condensed the best parts down
into Acoustics 101.
Are these tips the same ones you could get if you hired the "million dollar room" guys? In some
cases, yes they are. Are these tips guaranteed to give you the world’s best recording studio, one
that’ll test better than Oceanway and cost only $100 and 2 hours time to build? Not entirely, but we do
give you tips on how to build rooms that capture the essence of the million dollar rooms. (It should be
noted that we've been called in by clients quite a few times over the years to fix acoustical problems
the million dollar guys either [a] caused, [b] overlooked or [c] weren't able to solve at a price the client
could afford.)
What these tips will do is give you a solid basis of knowledge with which you can build a very
functional recording studio, listening room or production facility without having to beg the bank for a
loan. If you can follow directions, can think logically, have a little bit of money to spend and know how
to do basic carpentry while paying careful attention to detail, you’re well on your way to building
yourself a solid, quiet room! Then, once it’s built, if you treat your room with the appropriate Auralex
acoustical products, you’ll also have a great sounding room, one that’ll be a pleasure to work
in...create in.
I’m no longer a commercial radio personality, but I’m still active in freelance voice work for
commercials, messaging-on-hold, documentaries and more, and we’re building our production
companies, Captive Audience™ Inc. and Alien Multimedia, Inc., a new multi-studio digital audio and
video complex at our new headquarters. Everything you’ll read in Acoustics 101 is being put to use at
our own new facilities, so you know I personally place a lot of trust in these solutions.
I’m fully aware that there are loads of famous acousticians out there who have written books and
probably would be glad to spec out your new studio for you if you were willing to pay them $1200 an
hour or, in a few cases, no less than $50, matter how small your project. I’m also aware that
many of them know no more than we do and that many of them know even less than we do. While
the million dollar room guys can make acoustics seem like rocket science when it’s appropriate and
the budget allows (or when the client needs a dog and pony show to feel good about all the money
they’re spending for consulting), often you and I don’t need that level of tedium and expense. We
need somebody to give us good, easily-implemented advice. Acoustics 101 does just that.
Another thing you’ll notice: this booklet recommends that you use some of the products sold by
Auralex. Now, are you free to substitute other companies’ products if you choose? Sure you are;
nobody’s twisting your arm. But [a] we've giving you lots of free advice that'll save you tons of time
and money, so I think we deserve your support, and [b] you won't be able to find similar products that
exhibit all our products’ benefits and advantages at anywhere near our prices. This booklet is
intended to provide you with sufficient knowledge so you can make the choice for yourself that
Auralex products are simply the best available to you regardless of price. Even if you do ultimately
decide to use other firms’ products, though, we know you’ll have a better understanding of acoustics
and reap more enjoyment from sound in general having read Acoustics 101. If we can help facilitate
that for you, we’ve done our job.
So, enjoy! We hope it answers the questions you’ve had floating around in your head and that you
find the information it contains to be both easy-to-understand and useful. Now, get out there and build
a great room, make great sound, make great money and most importantly ENJOY YOURSELF. You
can do it!
Eric Smith
Founder and President ("Fearless Leader")
Auralex Acoustics Inc.
If you are reading this, you are very likely interested in improving your sound. The concepts put forth
in these pages are not new. They are not revolutionary. You can find them in many other texts. Our
hope is that our presentation and treatment of these topics will be “down to earth” and easier to
understand, putting complex concepts into perspective.
Acoustics is not all common sense. Unfortunately, the subject can sometimes be quite confusing.
However, we are confident that you can build a great room by following Acoustics 101. And there is
nothing stopping you from taking these concepts and coming up with even better ideas than what we
have presented herein. If you do, that’s great! Fax or e-mail us your ideas so future Acoustics 101
readers can benefit from what you have developed. What you are reading right now is the newest
incarnation of Acoustics 101. Many contributions from readers like you have been incorporated into
this “new and improved” version. The only thing about making changes is to make sure you have
really thought through the ramifications of what you are doing. Random substitutions could degrade
everything you are trying to accomplish. If you are unsure, contact us.
Some of the basics of how sound behaves are implicit in Acoustics 101. Some examples of concepts
we assume you have a basic understanding of include:
When sound strikes a surface, some of it is absorbed, some of it is reflected and some of it is
transmitted through the surface. Dense surfaces, for the most part, will isolate sound well, but
reflect sound back into the room. Porous surfaces, for the most part, will absorb sound well,
but will not isolate.
The best way to stop sound transmission through a building structure is to isolate the sound
source from the structure before the structure has a chance to vibrate.
Walls need to be isolated from ceilings and floors, usually by means of dense, pliable rubber.
The main ways to minimize sound transmission from one space to another are adding mass
and decoupling.
Limp mass is most often better than rigid mass (actually, a combination of the two is really
what you are after).
Every object, every construction material has a resonant frequency at which it is virtually an
open window to sound — kind of like a tuning fork that “sings” at its particular resonant
Different materials have different resonant frequencies.
Trapped air (a.k.a., air spaces and air gaps) is a very good decoupler.
Airtight construction is a key concept. Sound, like air and water, will get through any small gap.
(Sound can leak through openings as small as 1/32” – in some cases even smaller.)
Sound bounces back and forth between hard, parallel surfaces.
One of the single biggest concepts to understand and appreciate is that acoustic foam, one of our
core products, is not going to "soundproof" your room. It is an extremely effective absorber of
ambient, reflected sound and helps make rooms "sound better." Acoustic foam does contribute some
sound isolating properties (mostly high frequencies), but is not sufficient by itself to keep sound in or
out of a room. Thicker acoustic foam is better at absorbing low frequency sounds. Controlling
reflected sound within a room is extremely important in producing good sounding recordings. When
you hear Mike Wallace’s voiceovers on 60 Minutes, you might be surprised to find out that they did
not spend a million bucks on it. (It is amazing what some good 2" acoustic foam can do for a glorified,
yet well-constructed closet!)
Isolation construction – the core concept in Acoustics 101 – is not inexpensive. Acoustics 101 carries
with it an assumption that you have a few bucks to spend to make your studio the best it can be. For
example, it is important to realize that empty egg cartons, cork squares and carpet scraps are not
going to (a) keep sound from leaving or intruding upon your studio and (b) yield that pleasing, neutral,
"Mike Wallace" sound within your studio.
If the guidelines, tips, techniques and advice in Acoustics 101 are improperly implemented, the
desired results will not be achieved. Auralex cannot be held liable for the advice given because we
are not going to be there watching you do the work or assisting with the construction. Please note that
these tips are being provided on this website free of charge.
If you cannot handle a circular saw and other common power tools or you do not have the money to
hire someone who does, then you should probably stop right here. It is going to be difficult to
implement the advice given here if you or someone you hire cannot handle basic construction
methods, such as applying drywall tape and mud, creating solid, airtight and level partitions and
floors, "measuring twice; cutting once," etc.
There are myriad benefits to constructing your control room to be symmetrical geometrically and
building using the best materials you can afford. Money well spent now will benefit you for a long time
into the future.
One of the keys to getting good, clean sound on tape or hard disk is removing the sound of the room
from the equation, to one degree or another. For a great example of this objective successfully
implemented, listen to the Eagles’ Hotel California or Pink Floyd’s Dark Side Of The Moon.
Some of you will be able to grasp all this quicker than others. Please understand that any extra effort
you expend implementing the tips contained in Acoustics 101 will pay you back sonically for a long
time to come. Make no mistake: they are worth whatever work it takes to put them into practice.
For a complete treatment of acoustical terms defined, two additional sources are recommended
(besides the overview of the most important terms discussed in Acoustics 101):
Rane’s Pro Audio Reference (free web-based dictionary of audio and acoustical terms)
ANSI Standard S1.1-1994 ($150.00 – official, standardized acoustical definitions)
Acoustics 101 Definitions
Noise Reduction Coefficient (NRC)
NRC is a single-number rating representing and overview of how much sound is
absorbed by a material. Example: ½” gypsum board (“drywall”) on 2x4 studs has an
NRC of 0.05.
Soft materials like acoustic foam, fiberglass, fabric, carpeting, etc. will have high NRCs;
harder materials like brick, tile and drywall will have lower NRCs. A material’s NRC is an
average of its absorption coefficients at 250, 500, 1000 and 2000 Hz. In general, the
higher the number, the better the absorption. NRC is useful for a general comparison of
materials. However, for materials with very similar NRCs, it is more important to
compare absorption coefficients.
Absorption Coefficient (α)
The actual absorption coefficients of a material are frequency dependent and represent
how well sound is absorbed in a particular octave or one-third octave band. Example:
½” drywall on 2x4 studs has an absorption coefficient at 125 Hz of 0.29.
Comparing the absorption of materials should involve a comparison of their respective
absorption coefficients in the different bands. Provided the materials are tested in a
similar fashion, the material with a higher absorption coefficient in a particular band will
absorb more sound in that band when you use it in your room. Be careful though:
Materials are tested using different mounting methods. For example, if one material is
tested by laying the materials out on a predetermined area of the floor – called A
mounting – and another tests their materials by spacing them off the floor by several
inches, then the comparisons are “apples and oranges.” To truly compare, find numbers
derived from tests that used the same layout of materials in the test chamber. Also,
there are three main standard methods used to test materials for absorption. Two of
them are reverberation chamber methods – ASTM C423 in the U.S.A. and ISO 354 in
Europe. These two methods are quite similar, but the ISO method – in general – will
produce slightly lower overall numbers than the ASTM method. The other method is the
impedance tube method, or ASTM C384. This method places a small sample of the
material under test at the end of a tube and measures the absorption. Again, the
numbers from this test are usually lower since a different method of calculation is used.
They are also not as representative of real-world applications of materials relative to the
reverberation chamber methods.
Sound Transmission Class (STC)
STC is a single-number rating of how effective a material or partition is at isolating
sound. Example: ½” drywall has an STC of 28.
Hard materials like rubberized sound barriers, concrete, brick and drywall will have high
STCs. Softer materials like mineral fiber, acoustic foam and carpet will have much lower
STCs. Virtually every material filters out some of the sound that travels through it, but
dense materials are much better at this than are porous or fibrous materials. Like NRC,
STC is useful to get an overview-type comparison of one material or partition to another.
However, to truly compare performance, the transmission loss numbers should be
Sound Transmission Loss (STL or TL)
STL represents the amount of sound, in decibels (dB), that is isolated by a material or
partition in a particular octave or one-third octave frequency band. Example: ½” drywall
has an STL at 125 Hz of 15 dB.
Comparing material or partition performances should involve comparing the STLs of
each in the different bands. If both materials or partitions are measured in accordance
with the STL/STC standard, ASTM E90, then the comparisons being made will be
“apples to apples.” It should be noted that real-world performance is not going to
provide the same level of STL that is achievable in the laboratory. However, the relative
performance of one material or partition versus another typically holds true in real-world
construction. I.e., if the lab measures one partition better than another, it should hold
true for a real partition built in your studio. Even though an actual field test of a concrete
wall might reveal a field STC (FSTC) that is 5 points lower than the lab test, it is still
better – relatively speaking – than a simple, single-leaf, uninsulated drywall partition in
the same configuration.
This is the concept of detaching partitions from each other, or physically detaching
layers in a partition in order to improve sound isolation.
The most common methods of decoupling are:
Air gaps or air spaces between two partitions.
Using resilient channels (RC8 from Auralex) between layers and structural
framing members for walls and ceilings.
“Floating” a floor using springs, rubber isolators (such as U-Boats from Auralex),
or other decoupling layers.
Room Modes
A room mode is a low frequency standing wave in a room.
Normally, this is a small room phenomenon, though large rooms have (very, very low)
modes as well. A mode is basically a “bump” or “dip” in a room’s frequency response
that is facilitated by the room’s dimensions and the way those dimensions cause sound
waves to interact with each other. There are three types of room modes
Axial modes: Standing waves between two parallel surfaces.
Tangential modes: Standing waves between four surfaces.
(Click here for illustrations and further discussion of axial and tangential modes.)
Oblique modes: Standing waves between six surfaces. (Oblique modes are more
complex, higher in frequency and decay faster. Therefore, they are not typically a
big problem.)
For a complete treatment of modes, there are ample discussions in acoustic reference
books. There are intricate formulas in these texts that can help you determine your
room’s modes. There is also software that can do the same. We have developed our
own proprietary software and would be glad to work with you or your salesperson in
figuring your room’s modes to help steer you in the direction of the proper acoustical
treatments. (Note that rectangular rooms are the easiest to predict. Our software is
based on rectangular rooms. For non-rectangular spaces, we can assist to a degree,
but the software required to actually predict the exact modes – which Auralex does not
use – is much more complex.)
As mentioned before, mass and decoupling are the two components that are most effective at
stopping the transmission of sound from one space to a neighboring space. This fact is plain to see
when you examine the Sound Transmission Classes (STCs) of various types of walls. The following
illustrations of wall constructions represent a small sampling of the myriad possibilities:
Note: “Gypsum board” is a generic name. Brand names include “Drywall™” and “SheetRock™.” Also,
metal studs (instead of wood) will provide incrementally higher STC for each of the configurations
The following table gives a subjective equivalent for different STCs:
Subjectivity of STC
Subjective Rating
< 30
Normal speech heard and understood
Loud speech heard and understood; normal
speech heard but not understood
Loud speech heard but not understood;
normal speech faint
Loud speech faint; normal speech inaudible
Very good - minimum required for
> 45
Loud sounds faint
Excellent - design goal for most
professional studios
And finally, we would encourage the reader to review the STC FAQ for a more complete discussion.
Absorption Coefficients and NRC
The table below shows absorption coefficients and Noise Reduction Coefficients (NRCs) for some
common building materials. They plainly illustrate the need for specialized acoustic treatments in
studios that require well-controlled sound.
Center Frequency of Absorption
1000 2000
½“ gypsum board on studs (16” o.c.)
Painted concrete block
Window glass
Some other useful links include:
The Auralex Master Acoustical Data Table (PDF)
The NRC FAQ for a more detailed discussion.
A point that is worth reiterating here is the fact that absorption coefficients and NRCs are not
percentages. In other words, if a material has an NRC of 1.10, it simply means that more sound (on
average) is absorbed than a material with, say, an NRC of 0.50. A few more facts about NRC that you
may want to know when comparing acoustical materials:
NRCs can only be multiples of 0.05. For example, and a material that is reported to have an NRC of
0.72 was probably not tested in accordance with the standards.
Absorption coefficients and NRCs can only be reported for materials tested in accordance with very
specific mounting methods. Beware of absorption coefficients and NRCs that were “calculated” using
numbers that were only reported by the testing lab as “Sabins per unit.” (One of our competitors is
notorious for this.) Since there was not standard area under test, converting to absorption coefficients
and NRCs is forbidden per the ASTM standards.
A final thought
STCs and NRCs are both very useful numbers for comparisons. However, if two (or more) materials
or constructions are being compared and their STCs or NRCs are very close, the octave band or 1/3octave band data should be compared. This is discussed more thoroughly in the FAQs mentioned
above. Should you be unsure of how to make certain comparisons, please contact us and we’ll be
happy to assist!
In Acoustics 101 a few general materials, as well as specific Auralex products are discussed. You
may or may not be familiar with all of them, so we will cover them here in detail to get that out of the
way! Your local lumberyard or hardware store can probably guide you if you do not know exactly
where to pick up the items discussed, just be careful not to let them steer you wrong with
substitutions or deletions. What worked once to construct a tight, good-sounding recording studio will
always work because sound never changes. Auralex has no interest in reinventing the wheel, which
is exactly what we would be doing if we attempted to make claims that were counter to the proven
construction techniques that are “out there.” The methods and materials outlined here have proven
themselves to work many times over and should prove more than sufficient for your needs.
Also, with few exceptions, do not add multiple layers of the materials specified; in this case more is
not necessarily better due to diminishing returns. (For reasons we will cover, going from two layers of
gypsum board to four is a good thing. Going from four layers to six or eight, however, might not be
worth the added cost/trouble.)
You can construct a perfectly good-sounding, airtight recording studio with common, easily-located
materials. There is simply no "magic" material that you absolutely must use if you are to have a good
room. The materials discussed herein are available at any decent lumberyard and will not set you
back two years’ salary.
Common Construction Materials
Wood and metal studs and joists – construction framing members with which most of you are
familiar. The most common framing for walls is either 2x4 wood studs or 3.5” metal studs.
Which is more cost effective – metal or wood – will largely depend on the relative price of wood
and steel in different parts of the country. For acoustical purposes, metal does offer resiliency
benefits worth considering for maximum benefit. For those of you that are not used to building
things, bear in mind when figuring your dimensions that lumber is not really the actual
dimensions indicated by the name. For instance, a 2x4 is not; it is actually 1½"x3½". A 2x6 is
1½"x5½", etc.
Gypsum wallboard (“GWB,” “drywall,” “SheetRock”) is commonly available in ½” and ⅝"
thicknesses. It is far and away the most common building material in North America for interior
finish construction. Unless you have a home built prior to the 1950s, you probably have
gypsum board finish to your walls and ceilings. (Plaster on lathe was much more common –
and incidentally much better for sound isolation than gypsum board – in homes prior to the
construction boom of the 1950s.) Of particular interest to acoustics and construction with
gypsum board is the Gypsum Board Construction Handbook, published by the United States
Gypsum Company.
Plywood is usually ¾" (but is available in a variety of thicknesses from larger lumber yards)
and is either available with flat edges, or with tongue and groove edges for tight floor
The Particleboard family:
o Low density fiberboard, or LDF, is typically called chipboard. It’s the stuff out of which
most inexpensive, DIY furniture is made.
o Medium density fiberboard, or MDF, is more typical of shelving and loudspeaker
enclosures. It has some very good acoustical properties and we like using it for many
varied applications.
o High density fiberboard, or HDF, is also available, but is quite rare and quite heavy.
Very high-end cabinetry will often employ HDF.
o Oriented strand board, or OSB, is often used in residential construction as a low-cost
floor underlayment.
o Straight up particleboard is usually a version of LDF, but can also be the name given to
a higher grade of OSB.
Other materials we make mention of in Acoustics 101 include gypsum board screws of various
thread sizes and lengths, construction adhesives including vinyl flooring adhesive, silicone
caulk, etc. Wherever possible, we have provided make, model and cost information as
appropriate for any non-Auralex materials we mention.
Specialty Construction Materials
Soundboard is often misunderstood, so I will try to set the record straight here. Many people
mistakenly use the term to describe materials like regular gypsum board or even particleboard.
This is not accurate. Soundboard is actually a trademarked name for a brown, compressed
paper board that is usually ½” or ⅝" thick and is manufactured by the Celotex Company. The
best way to describe it for you here is to say that it is a lot like a sheet of Masonite or
pegboard, only thicker and a bit softer. A similar material is Homasote. If you describe
Soundboard or Homasote to your building materials supplier, he or she can probably direct you
to it. It is pretty dense, so it makes a good layer in a multi-layered wall configuration. In
conjunction with layers of ⅝" gypsum board, ¾" particleboard or MDF and SheetBlok, it is
really effective at blocking the transmission of sound. (It should be noted that when compared
side by side with gypsum board, Soundboard is not quite as good in a straight up STC
comparison. Click here for an illustration. It is not clear what sort of performance Homasote
offers versus gypsum board or Soundboard. Bearing that in mind, Soundboard is good if you
want to change up the composition of the layers in your construction. This will dissipate
resonances well. However, for sheer mass, gypsum board is a much more cost-effective
Blueboard is also a very misunderstood material. This is typically an expanded polystyrene
board that’s been dyed blue, though there are also pink versions available. It’s all the same –
mostly useless in terms of acoustical isolation. The density of the material is very low and the
material itself is a closed-cell foam. Thus, there is no mass benefit to be gained for isolation
and no absorptive benefit to be gained when using it in wall cavities. Unless there is a specific
code requirement for this type of material in your construction, we would encourage the use of
glass fiber or mineral fiber insulation products in lieu of blueboard.
Glass fiber insulation comes in many varieties. The most common is the pink insulation found
in many attics, walls and basements. Here’s a breakdown of the types of insulation, their
densities and their acoustical benefits:
o R-11 (2” thick) through R-30 (6” thick) “batt” insulation is very common. It has a density
somewhere between 0.7 and 1.0 pounds per cubic foot (pcf) and usually comes in rolls.
It is very effective at minimizing cavity resonances (resonances that occur in the air
spaces between framing members). It is the minimum insulation that should be used in
the walls, ceiling and floor of any studio construction.
o Board insulation is available from the various companies that specialize in the
manufacture of insulation materials. It is typically yellow in color and 2’x4’ or 4’x8’ in size
with thicknesses varying between ½” and 4”. You may hear it referenced using OwensCorning’s “700 series” designations, e.g., “703” and “705.” It is more effective than “batt”
insulation at combating cavity resonances. It also has a mass advantage since it is
offered in densities from 2.0 to 8.0 (or more) pcf.
o Either of the above can be purchased with kraft paper or “FRK” (foil-reinforced kraft
paper) facings on one or both sides. Two advantages the facings offer are (a) ease of
handling and (b) decreased high frequency absorption. The latter is achieved only if the
material is not physically inside the wall, ceiling or floor. Thus, if you have the option of
buying faced insulation, we would encourage it from the simple standpoint of not having
to deal with as much of the irritation associated with handling glass fiber materials.
o Ductboard is a variation of glass fiber insulation, typically 3 pcf and available in ½”, 1” or
2” thicknesses. There is usually and FRK backing on one side and a black scrim facing
on the other. Used inside ducts, this type of material can help minimize turbulent airflow
noise in HVAC systems. Since the black scrim facing contains the fibers, it can also be
used as a low-cost wall absorber. It should be noted that the ½” thick material is rare.
The 1” thick material is very common and is the minimum that should be considered for
any acoustical application.
Auralex Products
Studio-grade Mineral Fiber Insulation is a special, denser type of insulation that the top studio
designers are known to use to improve a room’s level of soundproofing. Its greatly increased
density when compared to the traditional, pink, glass fiber insulation makes it more effective at
stopping the transmission of sound from one room to another. Plus, our Mineral Fiber features
a much higher burning point than standard fiberglass insulation and has a radically lower rate
of moisture absorption. Our Studio-grade Mineral Fiber is available in 1", 2", 3" and 4"
thicknesses in 2’x4’ sheets.
SheetBlok™ Professional Sound Barrier is our proprietary, limp mass, dense, vinyl sound
barrier material available in 10’x4’ sections or 30’x4’ rolls. It weighs one pound per square foot
(1 lb/ft²) and is about ⅛" thick. It is flame retardant, easy to install with plastic-cap nails, staples
or trowel-applied multi-purpose vinyl flooring adhesive. We also offer SheetBlok-Plus which is
the same as SheetBlok, except with a very strong peel-and-stick adhesive backing that makes
installation a breeze. SheetBlok is safe, inexpensive, easy to work with, more effective, easy to
cut with scissors or an ordinary utility knife and is FedEx shippable right to your door.
SheetBlok is quite simply one of the best investments in good sound control that you will ever
make. Other SheetBlok links:
o Installing SheetBlok
o SheetBlok MSDS (PDF)
o SheetBlok Technical Data Sheet (PDF)
U-Boats™ physically decouple ("float") a floor without having to use rigid mechanical fasteners
like screws (and without having to take out a second mortgage!). U-Boats make quick work of
floating a floor at a price virtually anyone can afford. They are more cost-effective that the
"pucks" that have been used in the past. Famous studios and recording artists are using them
and loving them. Many multi-million-dollar studios and home-theaters-of-the-stars are floating
on U-Boats and you have heard them at work on numerous chart-topping records. Other UBoat links:
o Spacing U-Boats
o U-Boats and weight of floor
RC8 Resilient Channel is a piece of specially shaped metal to which gypsum board or other
building materials can be mounted to isolate them from the framing members (studs) of a wall
or ceiling. One leg of the Resilient Channel attaches to the stud, the other leg to the layer of
building material being hung. This isolation helps improve the structure’s ability to achieve
greater sound transmission loss. We sell RC8 in bundles of 24 that are FedEx shippable and
are available through your favorite dealer. Other RC8 links:
Other products discussed:
Tubetak™ Adhesive
Foamtak™ Spray Adhesive
StopGap Acoustical Sealant
show good designs
for those of you
vertical space to
spare and need to
float your floor (and
your walls). These
are perfect when a
studio and control
room are both going
either wooden or a
concrete slab. If
yours is concrete,
consider (carefully)
cutting a gap in the
concrete between
the two rooms first,
then proceeding as
shown. Cutting the
slab is no minor
you will be relieved
to know that if you
decide to do it, the
gap does not need
to be any wider
than the width of
the saw blade. N.B.:
The cut must bisect
the entire slab. If
you are unfamiliar
with the structural
doing this, please
cannot be held
responsible if your
building caves in.
show 2x6 joists and
2x4 walls, but if you
do not have the space you can use 2x4s, 2x3s or even 2x2s for the floor. The specific material used
may not matter as much as the proper implementation of the materials. I.e., the general method stays
the same. The preference if you have the space is 2x6 or larger because they allow for more trapped
air space and better overall decoupling. It is advisable to caulk all edges, seams and corners (as well
as any penetrations – more on that elsewhere) particularly where different materials meet. Leave
about a ¼” gap in parallel seams and perpendicular corners and use our new acoustical sealant,
StopGap™. (StopGap is an approved substitute for gypsum board “mud.” Tape and finish as you
normally would.)
If for whatever reason you cannot build your wall/floor exactly as pictured, be it a space limitation,
lack of funds, etc., first try to grasp the concepts used in the construction pictured. If you are serious
about wanting to stop sound transmission, it is imperative that you isolate the sources of sound from
the structure. Air and mass are your friends. Give strong consideration to making a layer of SheetBlok
part of your floor sandwich.
The sill plate (bottom framing member of the wall) actually rests on two layers of SheetBlok to
decouple it from the existing or floated floor. In a perfect world it would be preferable to glue the
SheetBlok to the bottoms of the wall plates and joists instead of nailing it; in fact, wherever possible
throughout the framing, glue any materials you can together rather than nailing or screwing them. The
reason gluing is always recommended is that the adhesive itself will contribute some degree of sound
isolation, too. Nails or screws serve as bridges acoustically and transmit sound from one layer to the
other too well, so you want to avoid them whenever possible. Pick screws over nails (preferably used
in conjunction with glue) because they form a tighter bond that yields fewer resonances. Example:
We suggest gluing the particle board down and caulking the seams and boundaries. Repeat for each
layer, gluing one atop the next. This makes fewer penetrations than if you screwed down each layer.
If you must screw the layers (this is very often the practical reality), be aware that it is not “the end of
the world.” Just be sure to go with the absolute least number of screws possible. We recently
completed a build-out on a new facility. You should be aware that most “drywallers” will simply use as
many screws as they think is necessary. Even as often as every 4”! This is far too many for acoustical
purposes. So keep an eye on any hired help and let them know that as few screws as they can get
away with is preferred.
Same goes for when you are anchoring the walls to an existing floor (Figure 3.1b). If you must bolt,
screw or otherwise secure the sill plate, use the least number of connection points that you can get
away with. And if you are anchoring to concrete slab, look into spending a little extra on isolated bolt
mechanisms. These devices provide rubber grommets for the solid bolt to go through so it does not
come into direct contact with your sill plate, thereby maintaining the level of decoupling you need!
When layering, subsequent sheets of material should be rotated 90 degrees so no seams line up (see
Figure 3.2; this staggering applies to wall, ceiling and floor materials) and, if used, the preferred
“tongue and groove” (T&G) materials should be glued together at each T&G joint. As mentioned
previously, all seams – regardless of material used – must be sealed up tight with something like
baseboard or other trim
you can line the bottom
weatherstrip tape to
help decouple it from
the floor if you are
installing flat flooring
like vinyl or parquet
instead of carpeting.
Naturally, if you are
installing carpet, your
carpet pad should be
densest you can afford and accommodate from a space standpoint; 8#, 1/2" re-bond carpet pad has
worked well for us under certain types of carpet like plush or Berber, while ¼" ComfortWear-200
(made by GFI and sold under a variety of trade names; it is usually purple or blue and has a
honeycomb pattern embossed on one side) works well under short-pile commercial-type carpet.
Where your raised floor meets the existing walls, it is better to build it in such a way that the two have
a slight physical separation (note the airspace in Figure 3.1b), but if you must attach them, run
StopGap at the juncture first before attaching the final wall layer.
Do you have pretty good isolation except for when, say, someone plays piano or acoustic drums?
Instead of constructing an entirely new floor, you can fashion an effective riser using Platfoam™ to
put on the floor under the offending instrument. A prefabricated riser is also available, the
HoverDeck™. This also applies to those of you in basements who do not want to frame new floors as
earlier described. Kenny Aronoff and many other famous Auralex users are using our PlatFoam and
HoverDeck. The amount of extra sound isolation you gain, as well as the dramatic improvement in the
purity of the instrument that rests on the riser, make either of them an all-around winner! Kenny
Aronoff is so impressed with his riser that he now has them in all the major recording markets with his
identical drum kits so no matter where he is playing, he can be on an Auralex riser. How's that for an
Auralex also offers a small, portable riser called the GRAMMA™ (patent-pending). GRAMMA stands
for Gig and Recording Amp and Monitor Modulation Attenuator, and it is designed to float guitar
cabinets, bass rigs, subwoofers, studio monitors, stage monitors and more for greatly improved
isolation and purity of tone. Tower of Power, Lee Roy Parnell and many other famous recording
artists are using GRAMMAs on-stage and in the studio and LOVING them! If you are unable to
construct your room to be as sound-isolated as you would like due to budgetary constraints, physical
constraints, etc., perhaps you can improve your sound AND your isolation by strategically
implementing GRAMMAs under some of your amps, monitors, etc. You will be quite happy and quite
surprised at the improvements!
In situations where you simply have no vertical room to spare or cannot install a floated floor, you
should consider floating a couple new layers of alternated T&G flooring on two layers of SheetBlok.
This yields increased STL and decoupling, but obviously does not give you the benefit of any trapped
air space.
There is quite a bit of debate about whether adding
“stringers” to your wall, ceiling and floor construction
is worth the effort. We believe it is a great benefit to
run stringers at uneven intervals between wall studs
and floor and ceiling joists before insulating them, as
shown in Figure 3.7. This helps tie the whole wall,
ceiling, or floor together so it is less likely to move
and transmit sound. As Philip Newell has pointed out
in many of his books, a stiffer construction will make it
less able to vibrate at lower frequencies. Our
research is ongoing and we certainly acknowledge
that stringers may not be completely applicable to
each and every construction. However, in the context
of Acoustics 101, we believe it is a necessity. I.e.,
since the budget for construction is usually tight, we
believe stringers to be a very cost-effective way to
help maximize isolation.
Figure 3.7 shows stringers mounted between studs or
joists. Stringers are short (14½" normally if your
studs/joists are 16" on center) pieces of the same
material as your joists that run perpendicular to the
joists and are nailed and glued between them in a
random, staggered fashion. It might seem like a pain
putting them in, but it’s time well spent. We know
because we have done it. We let people talk us out of
them once and lived to regret it!
structureborne sound
that is passing through
ceilings is much the
same – see Figure
3.3a. Generally, we
SheetBlok and gypsum
board either over the
preferably hung on
RC8 Resilient Channel,
or as part of a lower,
resting atop the new
walls. If you are lucky
enough to have vertical
height to spare, drop down 3½" and frame another ceiling resting it only on top of your new walls
(which, in turn, might be on top of your new floated floor). Insulate it with Mineral Fiber and cover it
with two (2) layers of ⅝" gypsum board mounted on RC8. If you have an unfinished existing ceiling,
insulate it with Mineral Fiber, cover the joists with two (2) layers of ⅝" gypsum board mounted on RC8
(you can use ½" gypsum board if you want, but ⅝” has been verified to be better if space, time, funds
and motivation permit) and then drop down 3½" and frame your new ceiling.
In reality, most of us fall into the "I do not have the height to spare" category. If that is you, you should
add a layer of SheetBlok to your existing ceiling and then add one (or two) layers of gypsum board
(½” or ⅝”).
Should you be in a situation where you need more sound isolation, but absolutely cannot add any
more gypsum board, consider adding a layer of SheetBlok Plus mounted with our pressure sensitive
adhesive. A piece of wood trim is recommended at each vertical seam and across the top and bottom
of each piece of SheetBlok Plus due to its weight. If the black color does not match your decor, your
SheetBlok Plus may be painted with high-quality latex paint (note that you may need to prime it first).
In order to use it as a finish layer, obviously you should be very careful during installation so as to not
nick up the SheetBlok Plus. By the way, while the pressure-sensitive adhesive (PSA) backing for the
SheetBlok Plus is very strong, we definitely recommend some type of mechanical fasteners be used,
too. Plastic cap nails, screws with grommets, furring strips at the edges, etc. have all been used with
good success. Also, for standard SheetBlok, multi-purpose flooring adhesive is recommended
because it is made for use with vinyl materials. We have not tried this type of adhesive ourselves, so
do not yell at us if it does not work for you.
No matter which method you use, the less light fixture boxes set in the ceiling, the better: They serve
as open windows to sound. Track lighting is preferred to recessed lighting and you should StopGap
any wire holes as outlined elsewhere in Acoustics 101 because holes sonically weaken a wall or
ceiling. So much so that in some instances people have virtually wasted their time. Floor lamps or
surface-mounted conduit may be your best bet.
(Non-)Flat Ceilings
Have you ever seen pictures of world-class studios? Sure you have. Have you ever seen one with a
flat ceiling? Rarely, if ever. The reason for this is that it is widely acknowledged that rooms with more
cubic volume (space inside them) sound better than small rooms. Why is this?
Small rooms tend to sound, well, small, because they have less space for sound waves to develop
and breathe. Think about it. In a 10’x10’ room, a sound wave that is traveling 1130 ft/s (feet per
second) can get from wall to wall to wall to wall in no time at all. This effectively means the room does
not allow time-delayed reflections to develop; reflections that would give the room a sonic "acoustical
space" signature. Implementation of good diffusors (such as Auralex T’Fusors™) can definitely help a
small room sound larger by properly diffusing the sonic energy in the room, giving the sound more
room and time to breathe. Further, digital delays and reverbs have improved enormously over the last
decade and we can now add our own "acoustical space" signatures to sounds — and best of all, only
when we desire to
have them. It is often
desirable to have a
drier room and add
rather than rely on the
room to interject the
ambience. The reason
for this is that there are
quite a few times when
desirable and other
times when a different
ambience than the
room has is desirbable.
Still, there are plenty of
where a
room’s ambient sonic
signature is desirable.
It is for this reason we
started this talk about
Discussing room sound
over lunch one time
with Ross Vannelli, he
hit the nail on the head:
"Once it’s on disk (or
tape), there’s no knob
for it."
unlimited budgets —
budgets big enough to
allow us to buy real
estate with as much
footage as we would really love to have. Does this necessarily and always mean that we are forever
resigned to suffer with tiny little rooms with flat ceilings? No way.
Square footage is expensive, but cubic footage is not. Look at Japan — what have they done?
Because Japanese real estate is at such a premium (i.e. they have run out of it), they have chosen to
grow up instead of out. We can put the Japanese principle to work for us in order to gain cubic
volume for our rooms. Maybe to a relatively small degree, but we can gain some amount of useful
cubic space to be sure. Non-flat ceilings are an easy way to do so. See Figures 3.3b-c for some
examples of good (and bad) ceiling designs. Also not that “cathedral” or “A-frame” ceilings can be
quite helpful in live rooms. (They are generally discouraged in control rooms due to focusing effects.)
Cathedral Ceiling Treatment for Live Rooms
Figure 3.4 shows an example of how we would suggest you to treat a cathedral ceiling for live rooms.
This also would work in a control room or studio room you have put in, for example, an attic space
because that’s the only place your spouse would let you! In it, we show 4" Studiofoam™ on the two
ceiling surfaces that come together to form the peak of the cathedral ceiling. Below that (the farther
down, the more effective it is), a horizontal piece of material forms the face of the “trap.” In this
example, the face material is ¼" pegboard and it is covered on both sides with 4" Studiofoam. Instead
of using two (2) separate pieces of 4" Studiofoam leading up to the peak, a viable and perhaps even
more effective alternative is to span the peak with a piece of Studiofoam, forming a small, triangularshaped airspace behind it. One way to control sound in general and low frequency sound in particular
is to force the sound waves to fight their way through multiple layers of different materials and dead
air before they can strike the room boundary.
You can also build the
faces of these panels out
of strips of 1x2, 1x3
(normally pine, but that is
your choice; based on
your budget you might
want to try oak or some
other hardwood). One
installing the slats in an
fashion (1x2, 1x4, 1x3,
1x3, 1x4, 1x3, 1x2, etc.)
and leaving spaces of
varying widths between
them (¼", ½", ¾", etc.).
The last variation on this
theme is to substitute
plywood, masonite, or
some other hard material
for the pegboard, caulking the it tight to the ceiling surfaces so you end up with a sealed, resonant air
cavity. This is technically known as a diaphragmatic or panel absorber. You can cover the face of the
plywood with Studiofoam to broaden the effective range of the trap and help control your room’s
acoustics. The Studiofoam inside the trap broadens the range of frequencies the trap affects, kind of
like changing the Q of a parametric equalizer.
The preceding three paragraphs have described perforated panel absorbers, slat-Helmholtz
absorbers and diaphragmatic absorbers, respectively. For more information on exact designs of these
devices – designs that will help you tune them to target a specific frequency range – please refer to
the titles – particularly the Master Handbook of Acoustics by F. Alton Everest – on our Book Referrals
page. Many of the titles are probably available through your local library.
Using any of these methods is viable; which you use is really up to you and depends on how much
time you want to put into the device(s). They all work, so just pick one depending on your needs.
Some people have even combined a couple of these variations. For example, wooden slats can be
placed over the face of the plywood for extra reflection and diffusion.
An often overlooked method of gaining extra bass trapping in a small room is to "steal" some of the
wasted space that may be above an adjacent room. Famous acoustician and talented surfer dude
Chris Pelonis (who has used LENRDs when 90° angles are involved) has built Helmholtz resonator
types of bass traps in the attic space over rooms adjacent to studios and control rooms. This is a
great way to give a room’s low frequency waves more room to develop and breathe and to utilize
what is often wasted space. Auralex implemented this type of adjacent trapping in our acoustical
design of the 1999 CEDIA Home Theater of the Year and the room tested flat (±3dB) from 70 Hz to
20 kHz. Down to 38 Hz, the room was subjectively flat; i.e., it had no audible peaks or dips. On paper,
this corresponded to ±6 dB down to 38 Hz. See the SJPT Case Study for more details.
Mr. T (Bar)
Many times a customer with an existing T-bar (suspended, or "drop") ceiling will ask if he should
remove it to expose the bare gypsum board ceiling above, then treat the gypsum board ceiling with
foam. If the existing ceiling tiles are the really cheap, not-very-absorbent type (the absorption
coefficients and NRC of which you might be able to verify with the help of your local hardware store or
lumber yard), then we would say “yes.” If the existing ceiling tiles’ acoustical properties are able to be
verified and the NRC is 0.75 or above, leave them, but over the top of them and the T-bar roll out at
least one layer of 4" Mineral Fiber or 6"-12" unfaced traditional insulation. Doing so not only helps
alleviate the reflected sound that can bounce around between the top of the suspended ceiling and
the gypsum board above, it improves the NRC of the ceiling as a whole, especially with regard to its
low frequency absorption. It is also likely to marginally improve sound isolation from whatever is
above the room, be it a neighbor or the great outdoors.
If you are in a space that has an existing drop ceiling that has decent NRCs, but you desire absolutely
the maximum amount of sound transmission loss from above and are absolutely unable to frame a
new false ceiling, we have a couple solutions for you. The first involves rolling out unfaced insulation
or Mineral Fiber as noted above then rolling out SheetBlok over the top of the insulation. SheetBlok
weighs 1 lb/ft², so some reinforcement of the T-bar suspension will probably be necessary. Overlap
the SheetBlok by at least an inch, then tape the seams with foil duct tape or at the least regular cloth
duct tape.
Cut SheetBlok to the size of each of your ceiling tiles, then glue it to the back of each tile or
simply lay it over them.
Buy T’Fusors™ and lay a piece of rigid material like 1" Mineral Fiber, SonoFiber, or even rigid
glass fiber board (preferably with SheetBlok cut to fit and glued to it) in the cavity molded into
the back of each T’Fusor. This yields improved diffusion, quite a bit of low frequency trapping
and improved isolation.
Some suspended ceilings are not the sturdiest things, so be sure to check yours out and make sure it
will support the weight of the composite panels before you go ordering the materials. Nothing ruins a
session like a heavy ceiling crashing down on top of you!
If you feel the need to install a suspended ceiling in a room where there is not one already, the tile
manufacturers recommend that it be dropped down from the existing ceiling 16" to 18" for the best
acoustic performance. We agree, especially if you implement the insulation over the top of it as
described above. Some ceiling tiles we would encourage you consider – in lieu of the “cheapies” you
get from the hardware store – are as follows:
Armstrong High-NRC tiles include Optima Open Plan and Painted Nubby Open Plan.
USG High-NRC tiles include (PDF downloads) Orion 270 ClimaPlus and Premier Nubby
For those of you sharing space with neighbors, especially in commercial settings, a commonly
overlooked route of sound transmission is the space above the drop ceiling and over the wall
separating you from your neighbor. Many times this area will be totally open, so the only things
stopping sound from your neighbor getting to you (and vice versa) are your and your neighbor’s
ceiling tiles. This will typically provide an STC of only 10-15. Grossly inadequate for sound isolation –
especially a studio! There are two main solutions to this problem:
1. Replace your ceiling grid or – ideally – both ceiling grids with a solid, drywall ceiling as
described above.
2. Continue the common wall up to the roof or floor deck above, seal it airtight, and possibly
consider adding to its construction as outlined below in the section on Walls.
At the very least, SheetBlok hung vertically above the wall and sealed as tightly as possible to the
structure can help. The more airtight the better, so grab your caulking gun and go wild.
If you have already leased such a space or are contemplating doing so we would encourage you to
bargain with your landlord; ask him to share the expense of making the space habitable for your
needs. Many landlords will step up; a landlord who is in it for a quick buck will not and will likely be
tough to deal with down the road.
Unfortunately, the basic walls built in most homes and businesses are simply not dense enough or
thick enough to be good barriers to neighboring sound. This page will show you proven methods for
adding additional layers of materials to your existing walls to make the most of them. For those of you
doing new construction, these tips are applicable as well. The choice of how to retrofit your existing
walls, ceiling, etc. is entirely up to you, your ears and your pocketbook.
Existing Walls
First, determine as best you can what the materials are which comprise your existing walls. You hope
you find out that you have 2x6 walls, heavily insulated and caulked, floated on SheetBlok, then
covered with a layer of ⅝" gypsum board, a layer of SheetBlok, a layer of ½" gypsum board and
surface treated with Studiofoam.
If so, go directly to Park Place, collect $200 and have dinner at a fancy restaurant. If not, read on.
If your problem sounds severe to you and you learn that the existing wall has no insulation in it, it is
advisable to install Auralex Mineral Fiber in it by removing the gypsum board and placing the Mineral
Fiber between the wall studs. Alternatively, you can look into blowing insulation into the wall with a
machine (see your local hardware store for details).
Having done that, the more closely you can retrofit your wall to resemble the one shown in Figure 3.5
above, the better off you will be. You can choose to alter materials or leave off layers, but the
performance of the wall may be lessened, so delete or change at your own risk. Naturally, you should
use good construction techniques, taping, mudding and caulking seams all the way, making sure to
stagger all seams and
rotate adjoining layers
90° from each other.
If you determine your
problem to be relatively
minor, you might be able
to get by with as little as
adding one (1) more
layer of gypsum board. If
you previously found out
your existing wall is one
layer of ½" gypsum
board or plaster on lathe
(older homes), add a
layer of SheetBlok and
then another layer of ⅝"
gypsum board.
Do you want to go to the
trouble to fur out from your existing wall to hang your new wall boards on? We think so. It is neither a
waste of time nor money and, if you have both, we would encourage it...but with a twist. At least cover
the faces of the furring strips with strips of SheetBlok (it is considerably more effective to actually
mount a layer of SheetBlok across the faces of the furring strips versus just putting strips of
SheetBlok on the furring strips' faces, but it also costs more). Then mount RC8 across the furring
strips. Then mount a layer of ⅝” gypsum board to the channels.
If you have the opportunity to build your space taller, allowing for a false/lowered ceiling and giving
your studio more cubic space, then you are indeed lucky. If that’s the case, there are a few things to
note that you might implement to improve on the wall/ceiling described above.
You should definitely build a "room within a room," meaning that there is air space and no
physical contact between the exterior walls and the new walls of your studio! There is no
substitute for doing it this way. You can build just one wall and can add layers to the wall until
you are blue in the face and poor as Patty’s pig, but chances are that you will never achieve
the level of sound transmission control you will if you go the extra mile and build a room within
a room. You know what they say about an ounce of prevention being worth a pound of cure?
In the practice of acoustics, an ounce of prevention is worth considerably more than a pound of
Sound can slip through very tiny gaps (1/32” and smaller) which might seem to you to be
insignificant. So it is of extreme importance to construct your place as airtight as humanly
possible. When humanly possible is not good enough, StopGap can be of great benefit. The
specific gaps we are talking about here are, e.g., the gaps around electrical boxes (remove the
outlet and switch plates to find them), underneath door trim, baseboard, crown-molding,
around HVAC vents (remove the grilles to find them), and so on. This is all part of the attention
to detail we’ve been talking about!
Never mount electrical
boxes or connector
panels back to back;
always stagger them
as shown in the Figure
3.6. Seal the holes
your wires go through,
or (preferably) run wire
insulation in the ends
to help seal it. Isolating
the conduit from the
SheetBlok or hanging it
with resilient hangers
can really offer some
control is a game of
Of course, the less wires and boxes you have poking holes in your walls, the less chances
sound has to get through where you do not want it. It may be prettier having all your boxes
flush mounted, but there is a lot to be said for surface mounting your phone cables and jacks,
audio connector boxes, light switches, etc. Not only does this method yield better isolation,
your artsy friends might consider you "retro", "industrial" and just plain "cool." Studiofoam and
other Auralex treatments applied to room surfaces can often mask surface-mounted goodies.
It is always better to keep wires away from each other than in big globs; especially audio,
video, data and phone lines that might be in proximity to electrical wires. If wires have to cross,
doing so at a right angle lessens the chance of interference occurring. Otherwise, keep all the
different typs of wires at least 12” away from each other and use shielded cable wherever
Other than the above, the wall construction we generally suggest is shown in Figures 3.1a-b from the
section on FLOORS.
The best common doors to use are exterior grade, solid-core wood (“slab”) doors that are flat, without
moldings. Also common, but more expensive, are commercial and/or exterior grade insulated steel
You can add SheetBlok to one or both sides of either type of door before installing the knob to
provide additional transmission loss, then Studiofoam over the SheetBlok.
If you have the inclination, you can make a door sandwich out of two (2) solid-core doors and a
couple layers of SheetBlok in the middle (this is the sort of thing Eddie Van Halen did at his 5150
studio). If you desire to have the ability to lock your door, be sure you can find a knob/lock that will
work with your thicker-than-normal door.
Double doors (backto-back) are of some
benefit if they are (a)
physically separate
door jambs that are
floated, and (b) are
as far apart as
possible given the
constraints of your
Build your walls and
double doors in such
a way as to give you
as much dead air
space between the
doors as possible.
Figure 4.1 shows
methods of installing
back-to-back doors
for single and double
Alternate your door
knobs and hinges left
to right. You can add
surface moldings to your slab doors if you want to dress them up. Install Studiofoam on your doors –
especially the sides that face each other. This absorbs any resonance that might occur between
The biggest reason that doors are poor in the area of sound control often has little to do with the
physical construction of the doors themselves (if you are using one of the types outlined above). The
weakest link in most door systems is that they are not sealed well with the floor below them or with
the frame around them. You must use a compressed rubber threshold below your door and you must
make sure that wherever the door shuts and would normally contact the door jamb it meets foam
weatherstrip tape or a rubber gasket. Magnetic seals can also be used, like you would find on a
refrigerator door.
For those requiring the ultimate in door seals, you might contact Zero International. They specialize in
door seals that do a fantastic job of blocking sound.
If you are looking to save yourself a considerable amount of time (and headaches), you might
consider simply specifying some sound-rated doors right into your studio. While they are expensive,
sound-rated doors give you far superior performance to anything you could do with a single door on
your own. Manufacturers of high-quality acoustical doors include:
Industrial Acoustics Company
Overly Door and Window Company
At most, you can expect an STC-30 to 32 from even the best solid-core door. The best double-frame,
back-to-back solid-core door arrangement rarely yields better than STC-50. By contrast, typical
single-leaf doors from the manufacturers above can yield ratings of STC-55 and higher. Worth
considering if maximum sound isolation is your goal.
Garage doors
The concept of the overlapping doors spoken of and diagrammed above is easily adapted to a
solution for leaky garage doors, especially if you break down the solution into multiple "bi-fold" type
doors that seal well where they meet. The better solution, however, is to build a false, floated wall
next to the garage door that does not come into contact with it and is isolated as well as possible from
the existing structure using the methods described in CHAPTER 3. If your budget permits, placing a
layer of SheetBlok over the interior face of the door before framing your new wall is advised. Most
garage doors leak water, so you might want to raise the garage door the width of a 2x4 and then nail
a treated, weather-resistant 2x4 under the garage door (floating the 2x4 with SheetBlok and sill seal,
available at your hardware store) and caulking with StopGap where it meets the concrete, door frame,
etc.). Having done that, lower the garage door down to it and nail up a 2x4 above the top interior edge
of the garage door to keep it from being raised. You are then protected from water and thievery and
everything you have done can easily be removed in the future should you or a subsequent property
owner desire.
Many of you will be building studios in your basement and sound traveling up your stairwell may
prove to be a problem. If possible, enclose your stairway and put a good, solid-core door at the
bottom to keep most of your sound out of the stairwell. In addition, or if enclosing the stairway just is
not feasible, apply as much 4" Studiofoam in the stairwell as possible to absorb as much ambient
sound as you can, thus making less sound available to travel upstairs. Stairwells tend to resonate
quite a bit, so if you are enclosing and adding a door, do everything you can to float or at least really
bulk up your new construction. If building an airlock or “sound-lock” (a small room separating one
sound-critical space from another and into which each of those rooms’ doors opens), float everything
you can, use SheetBlok copiously and treat the walls and ceiling with the thickest Studiofoam you can
afford. If you have the know-how to build a window into the door – or you can afford a sound-rated
door with a window built-in – this sound-lock can often serve as a vocal or isolation booth.
Often, it is relatively easy to add in a second
window if you are already building a second wall.
If you are going to do this, i.e., install a second
pane of plate, insulated, or laminated glass,
make sure the panes are as far apart as
possible, are parallel to each other, and never
touch wood framing of your new wall. The
windows should only come into contact with
SheetBlok, foam weatherstrip tape (FrostKing
3/4" wide by 7/16" thick, closed-cell, heavy-duty,
interior/exterior recommended) or StopGap. You
can either route out grooves for the glass to fit it
or just block it in with small wood slats. Line the
frame of the air space with Studiofoam to absorb
standing waves and throw some packets of silica
gel in between the panes to absorb the
condensation that invariably forms there. See the
Interior section below for more information.
Figure 4.2 — Clear SheetBlok™ in use at Perfect Sound Studios
Examples of exterior window isolation:
1. We recently helped drummer-extraordinaire, Kenny Aronoff, design and construct his new
studio. Kenny had already purchased and installed some decent windows, but was concerned
that they might not be as soundproof as he needed them to be. We sent a couple members of
our Engineering department down to Kenny's place and were pleasantly surprised when his
testing showed that the windows were "soundproof enough.”
2. Around the same time, we helped Joe Kasko with his new facility, Perfect Sound Studios. (As it
turns out, Joe is actually a friend of Kenny's. Small world!) When we were brought into the
project, conventional windows had already been installed. They were not quite good enough to
prevent sound from leaking out and bothering the neighbors behind the studio. In lieu of
trashing the windows and losing the investment that had already been made, Auralex
personnel devised – and Joe implemented – some "plugs" for the window openings using
Clear SheetBlok, 1x3s and other materials. The results were great and our testing showed that
they cut the level of sound transmission dramatically. When installed, the window plugs still
afford the ability to see outside as shown in Figure 4.2. (But not perfectly because Clear
SheetBlok is not as perfectly clear as glass).
[Worth noting is that Perfect Sound Studios has implemented the full Auralex arsenal from
construction products to absorbers and diffusers (some of the coolest painted T'Fusors we
have seen). The place looks and sounds awesome! ]
A double window between a control room and a studio is often used because single-paned windows
are very poor at stopping sound. You want to try to keep the panes parallel to each other to maximize
the dead air space between them and you do not want to use three panes because using three panes
actually lessens the contiguous dead air space. If you must angle your glass, angle only one pane,
not both, and make it a slight angle
going up, as shown in Figure 4.3.
Note that if you cannot angle the
glass by at least 8°, you are
No matter how you decide to
construct your window, a good way
to really clean your glass prior to
installation is to mix 1 drop Ivory®
dish soap gently with one (1) gallon
distilled water. Or just use a
Windex®-type glass cleaner. Do a
good job because you are going to
have to live with any smudges for a
long, long time! Wearing cotton or
rubber gloves while installing the
glass is recommended.
Figure 4.3 shows the preferred method of constructing your double-paned window. Make sure glass
never touches wood and float the whole construction on SheetBlok to isolate it from your control room
and studio walls. Throw a couple packets of silica gel into the dead air space to absorb unwanted
moisture that could fog your windows. Line the inside perimeter of the dead air space with Studiofoam
to help cut down on resonance.
And just so we are all on the same page in terms of the different types of glass:
Plate glass is simply a solid piece of glass. This type of glass typically has the worst
performance in terms of sound isolation.
Insulated glass is actually two (2) thin pieces of plate glass separated by an airspace. There is
an airtight frame around the glass and this type of glass is a pretty good performer in terms of
isolation. You can also find insulated glass that fills the space between with an inert gas like
argon. This does offer you an advantage since the speed of sound in argon is different from
that of air. This is known as an impedance mismatch and can give you a slightly better STC.
Finally, the best glass performer, in terms of sound isolation, tends to be laminated glass.
Laminated glass is much like insulated glass, except in lieu of a airspace, there is a laminate –
i.e., a clear glue. This is an even better impedance mismatch than that provided by the
insulated glass. We strongly encourage the use of laminated glass for any studio.
A final note about glass block: Glass block is often desirable when natural light is welcome, but prying
eyes are not. Glass block tends to be a great sound performer. There are typically two varieties: Solid
block and hollow block. The neat thing is there is not much of a performance difference between the
two because the hollow block is actually evacuated. This happens when the two pieces of glass are
superheated to fuse them together and form the hollow block. The air trapped inside the cavity is also
at thousands of degrees when the block is formed. As it cools, the volume of the cavity is constant,
but the temperature drops considerably. When this happens, the pressure drops to next-to-nothing
(Boyle’s Law for you propeller-heads), which we call, for all intents and purposes, a vacuum. Since
sound cannot pass through a vacuum, this is very advantageous for sound control. For some great
choices in sound-rated glass block, we highly recommend the products manufactured by Pittsburgh
HVAC stands for “Heating, Ventilation and Air Conditioning.” To control noise in HVAC systems
requires attention to many, many details. You should note that with regards to minimizing HVAC
noise, we can guide you along the right path. However, we do not pretend to know how to design the
right HVAC system for your studio with regards proper comfort, temperature and humidity control. If
you are very serious about controlling noise in your HVAC system, one thing to consider is hiring an
expert versed in the American Society of Heating, Refrigeration and Air-Conditioning Engineers
(ASHRAE) guidelines on HVAC noise control. Alternatively, you could order the (very expensive)
Handbooks and educate yourself. Of course, we will attempt to summarize here the many concepts
covered by ASHRAE and other experts in the field of HVAC noise control.
Whether you are in the process of building a studio, or converting a room into one, chances are the
question of how to heat, cool and/or ventilate it has crossed your mind. There are a few important
things to remember with HVAC and studios:
1. Even if you do not need heating or cooling, you need ventilation. People need to breathe and
they need to breathe the freshest air available. Stale air cannot only give a “bad vibe”, but it
can be unhealthy. Even if you are fortunate enough to live in a fairly temperate climate, airflow
is going to be essential for maximizing the studio experience.
2. HVAC noise can ruin recordings. There is nothing more unprofessional than tracking with a
“hiss” or “rumble” of a poor HVAC system in the background. You hear a lot in our industry
about “signal to noise ratio”. This often refers to gear and how much electrical noise is
introduced into the signal chain by a device, such as a preamp. HVAC contributes a different
kind of noise. Noise that cannot be reduced by buying a more expensive DSP.
3. Location for HVAC can affect sound. Research has shown that even small temperature
gradients in studios can cause imaging problems. Improper location of air duct openings can
inadvertently screw up an otherwise top-notch mixing environment.
Some of the advice that follows in this section is common sense. Some will only make sense to your
HVAC designer/installer. We are basically going to follow the “signal chain” in terms of airflow. Thus
we begin with…
The Air Handler
In most residential cases, this is your furnace, air conditioner or heat pump. (Or perhaps a
combination of one or more of these.) From here on, we will refer to all of them using the general term
– air handler. When selecting the proper air handler, it may surprise you to find out that bigger is not
necessarily better here. But neither is smaller. It is very important to select an air handler that is sized
exactly for your airflow needs. This will ensure it operates at optimum efficiency. And an efficient
machine is a quiet machine. If you are adding on new ductwork to an existing air handler in your
home, you should consider contacting an HVAC expert to make sure you are not overloading your
system. In cases where you are building into a basement, this is probably fine, as the air handlers put
on the home should already be sized correctly. If you are adding onto your home, though, you might
be asking the air handler to do more work than it was required to do.
The above assumes that the location of the air handler is already fixed. If you are doing a complete
build-out of a studio, you need to consider the three things (borrowed from real estate) that matter for
low noise HVAC: Location, Location and Location! Put the air handler in a room that is physically as
far away as possible from anywhere you will have open microphones or where you will be doing any
critical listening.
Another common feature in studios is the “window unit.” While window units are not recommended in
general because they require a window or some opening in the studio that could let sound in or out,
sometimes there is no other choice. We have yet to find a “silent” window unit, per se. However, the
GE Zoneline® series of air conditioners tends to offer a wide selection of quiet units.
Of course, if you are on a limited or nonexistent budget, try turning off your
thermostat when you know you are going to
have open microphones so the HVAC does
not kick in at a crucial time. If you are cooling
your space with a window air conditioner, you
might also consider constructing a "trap door"
or temporary cover that can be opened at
will. As shown in Figure 4.4, it is crucial to
isolate the frame from the wall and from the
doors by using SheetBlok at the junctions or
lining them with foam weatherstrip tape. The
doors should be routed at the closing junction
so they overlap and this junction should be lined with weatherstrip tape. Instead of making the frame
one layer of material, two (2) layers of different materials glued together is beneficial (if space
permits), especially with SheetBlok between them. Should you desire the frame to be removable, it
can be attached to the wall with angle irons (L brackets). Do everything you can to isolate the frame
from the wall and the doors from the frame.
The Fan
The fan (a.k.a., the “blower”) inside your air handler tends to be the single largest producer of noise.
(Except the compressor. But the compressor is usually located outside, on a roof or in a crawl space.
If there will be a compressor near your studio, make sure it is in a separate, well-isolated room.) You
should have already gotten off on a good foot if you selected an air handler of the correct size for your
application. The other thing to find out is if the air handler comes with, or can be equipped with an
insulated plenum. Most residential units do not come with this sort of feature or option. It might be
possible, however, for your HVAC expert to help you design a large box in or attached to your air
handler between the fan and the supply and return ducts. This box should be larger than the supply
or return air opening and should be lined with (minimum) 1” thick ductboard or its equivalent. Think of
this like putting a big muffler on your air handling unit. This plenum will absorb noise from the fan and
its motor.
Connecting the air handler to the duct work requires a little more than a pair of tin snips if you want to
minimize noise. Your HVAC expert should be able to help you select the correct flexible connections
to put between the air supply and return and their respective main ducts. These types of connections
are essential to help prevent vibrations from the air handler from traveling down the duct.
Ducts carry the air to and from your air handler. Most homes have a branching supply system with a
large, central “cold air return”. Commercial spaces will rarely have a ducted cold air return. More
often, the air is simply sucked up through the plenum, i.e., the air space above an acoustical ceiling.
(This is not the same as the plenum described above for quieting the air handler fan.)
For any ducted system, some key things to keep in mind:
Over-sizing the ducts is a good practice. If you have an HVAC expert in the loop, he/she will
have figured the airflow required for each room in “CFM” (cubic feet per minute). To find out
what size you should make the ducts, divide the CFM by the cross-sectional area of the duct in
square feet (ft²). Example:
o 500 CFM required.
o 12” round duct yields π*(0.5)² = 0.785 ft² (remember π*r² is the area of a circle and 0.5
feet is the radius of this particular duct example)
o Therefore, the air flow velocity will be 500/0.785 = ~637 FPM (feet per minute)
Any result you get for the above under 1,000 FPM is good. Below 500 FPM is excellent.
Use round ducts for minimal low frequency noise. Use round, insulated ducts for minimal low
and high frequency noise. Use round, insulated, flexible ducts for the best results, but do keep
in mind that since there is no sheet metal, sounds could “break-in” to the ducts from spaces
they are passing over or through.
Avoid very sharp bends in the ducts. Where bends are necessary, make sure they are gradual
and – if possible – include long, radiused turning vanes.
If the ducts are sheet metal, you may need to isolate them from the building using isolating
hangers. (You can Google this to find some vendors.)
Do include some bends
between the air handler or
main trunk and the studio
room. Bends reduce noise,
but only if they are gradual
and preferably equipped with
turning vanes.
If installing a new HVAC
system and ductwork, make
sure that you do not have
rooms that are fed by the
same main trunk. Instead, add
an additional trunk line and
feed each other room as
shown in Figure 4.5.
you might even consider
terminating your duct into the
space between two wall
studs, which you can line with
fiberglass board, then venting
that space into the room. We have seen this done and it proved to be very quiet!
Where the duct normally terminates in the wall or ceiling opening, consider an oversized boot
instead. Some pictures of a ductboard boot we built for one of our labs are shown in Figures
4.6a and b. We used 6” round, flexible, insulated duct that terminated into a ductboard box
roughly 17” long x 12” wide x 13” deep (into the ceiling). The whole boot should be caulked
airtight and isolated from the wall by SheetBlok or foam tape to keep from transferring
mechanical energy to the wall and making it resonate.
Finally, avoid putting ducts in walls shared with other noise sensitive or noise producing
spaces. This will create a weak link in your wall construction.
Figure 4.6a — Silent duct boot, grille closed
Figure 4.6b — Silent duct boot, grille open
The final links in the chain are the air devices. These are the “grilles,” “diffusers” (not the acoustical
kind), “registers” and “vent covers” that go over the duct opening in the room. When considering
devices like these – for supply or return air – you should try to find out the “NC” (“Noise Criteria”)
rating for them from their respective manufacturers. These are noise ratings that the device
manufacturer must provide for all possible airflow rates. For a studio, you should choose a device that
has NC-30 or lower for the designed airflow rate. Actually, NC-30 is the highest you should consider.
It should be quite easy to find a device that is “off the charts.” I.e., it doesn’t have a rating because it
did not produce any noise when tested at your airflow rate. For a good selection of quiet air devices,
check out on of our preferred manufacturers, Titus.
Do not locate your terminations anywhere above the mix area, especially between your ears and your
monitors, because moving air and different (even small) temperature gradients distort sound waves.
This will skew your imaging.
Again, we would encourage you to hire an expert to help you with all aspects of electrical wiring and
hookup in your studio. For electrical noise concerns, we offer some tips:
House computers, amps – basically anything with fans – in a separate equipment room. Build
this room just like you would build an isolation booth. The only thing to keep in mind is the
cooling required by many electrical devices. (Otherwise, they wouldn’t need the fans.) So be
sure not to miss the HVAC section.
If you do not have the space for a separate booth, consider at least housing some of your
noisy computers and amps in equipment from Sound Construction and Supply, makers of the
If possible, install separate circuits to power your room(s), or even various components of your
room(s) such as lights, HVAC, computers, audio processing, audio power amps, etc. While it is
of supreme importance to keep all your gear tied to a common ground at the electrical panel,
splitting things off on their own circuits lessens the possibility of various pieces of gear, lights,
etc. from causing AC problems for each other.
Avoid fluorescent lights because they can introduce noise into your room and into your audio
systems. While dimmers, in general, are also to be avoided, we do have some information on
quiet dimmers. We have compiled a PDF of some dimmer discussions that have taken place
on Syn-Aud-Con and
Keep power lines and audio/video/phone lines away from each other and never parallel.
Plug your gear into spike/surge/brownout protection devices and make sure your insurance
policy covers your gear if lightning should take some of it out. (Phone devices and computers
are especially prone to this; we have suffered these sorts of losses in the past.)
Live near extreme RF (radio) interference? Ask your electrician about constructing a Farraday
cage; basically a chicken wire or aluminum foil room within a room that ties to your ground rod
(seek professional assistance with this so you do not toast yourself).
To really clean up your ground buzzes and hums, and to greatly lower the overall noise floor of
your productions, look into the balanced power conditioners and other helpful devices
manufactured by Equi=Tech, ETA, Jensen Transformers and Furman. Of particular note are
the Jensen white papers. The folks over at Jensen are very much of the same mindset as
Auralex: We both believe that the problems for which we manufacture products are the last
anyone thinks about – i.e., acoustical and electrical noise problems. Anyway, all the products
from the manufacturers above do a fantastic job and can really save your fanny when your
best grounding and isolation intentions go awry. Of course, if you do not have the money for
them, Ebtech makes some wonderful 2-channel and 8-channel hum eliminators that really
work well. We have used them in mobile and studio racks.
Many times a studio owner will build a decent wall then sabotage himself by nailing up a shelf to
support his “nearfield” loudspeakers, or “monitors.” The problem with this is the monitors generate
high SPLs (Sound Pressure Levels), transmit the sound through their cabinets and into the shelf, then
the shelf excites the wall and transmission throughout the rest of the structure occurs. So, if you must
rest your monitors on shelves, do what you can to isolate the loudspeakers from the shelves and the
shelves from the structure, such as covering the shelves with a layer or two of SheetBlok or Platfoam.
If supporting your shelves with angle irons (which are not pretty if left exposed, but very functional
and easily hidden with Studiofoam), place a strip of SheetBlok or foam weatherstrip tape on the back
of each angle iron, then screw it to the wall, preferably using plastic wall anchors with your screws
whether or not you are screwing into wallboard or directly into studs. The plastic anchors actually help
filter the sound traveling through them.
Another monitor mounting solution is to suspend your monitors from the wall or ceiling by using
rubber tie down straps and eye bolts. The eye bolts should be screwed into sturdy studs and into the
monitor cabinets at sturdy points. From there, rubber tie down straps can be used to adjust the
monitors to the required angles. The obvious advantage of using rubber straps instead of metal chain
is that the rubber straps help better isolate the monitor cabinets from the structure. Please be careful
doing this because we do not want – and are not responsible for – your monitors falling on your head.
If you intend to set your monitors on shelves that rest on or overlap the top of your console, it is
important to not only isolate your monitors from the shelves with SheetBlok, rubber feet (Radio Shack
part # 64-2342), or our highly regarded MoPAD™ monitor isolation pads, but also the shelves from
the console. Remember that everything resonates (vibrates) at a certain frequency – even consoles –
thus producing unwanted sound. Also, do not forget to place Studiofoam pieces on the top of your
meter bridge to stop those pesky early reflections.
For those of you who have large monitors that are to be flush or “soffit” mounted in your walls, the old
school of thought about resting them on concrete-filled cavities has generally been debunked. These
days we know that concrete is so dense it transmits sound very well, so it is better to simply build
good, sturdy soffits, then place the monitors in them using the aforementioned methods to isolate the
monitors from the soffits. The inside spaces of the soffits themselves can resonate, so damp them
appropriately, by floating them from the floor and walls and by lining them with SheetBlok, then lining
the soffits with Platfoam so your monitors are “wedged in.” Be extra careful when constructing your
soffits to make sure the monitors are at precisely the same downward angle and precisely the same
distance off the center line from your mix position because, as you may know, you and your monitors
should form an equilateral (all sides the same length) triangle, otherwise you will forever think your
channel balance is off. For more great help on soffit-mounting – including construction details – check
out the SAE Reference Material site and click on the “Construction” link on the left side, then on the
“Speakers” tab that appears at the top of the page.
Angled Surfaces
It is fairly common for folks to think of angled walls when considering building a recording or
broadcast facility. A common misconception is that angled walls can be of benefit in the control of
room modes. Not so; you will still need “bass traps” in rooms with angled walls.
The good thing about angling is that it can certainly minimize instances of flutter echo (higher
frequencies) if done correctly. It then becomes essential to know how to do angle correctly. Before we
get into some suggestions there, let us point out that, in many cases you are going to be treating your
room(s) with Auralex acoustic products. Our products will work whether you have angled walls (and
ceiling) or parallel walls (and flat ceiling). So if you do not wish to go through the trouble, there is little
need to attempt to alleviate standing waves and room modes with angled walls; our absorption and
diffusion products are going to alleviate them for you. The main point is if you try to build an out-ofsquare room and get it wrong, you are going to be in a world of hurt and will end up spending more
on building materials and acoustic treatments in the long run.
If you do not mind a bit of a challenge, here are some key things to note when angling your walls:
For control rooms, symmetry is very important. One wall out-of-square is not a good thing.
If the total angle of “splay” is not between 8° and 15°, you are wasting your time. E.g., your
ceiling should be angled 8° to 15° from front (low, in front of you) to back (high, behind you). If
you are taking two parallel walls and angling them in opposite directions to each other, do it
equally with half the splay for each
Table 5.1: Sample room dimensions that are "ideal" based
side. I.e., 4° to 8° on each side
on two commonly accepted criteria (c.f.)
should be a design goal. For an
Eleven Studio Room Dimension Suggestions (Courtesy of
example of this, we will be discussing
the “Acoustics 101 Room” shortly…
Finally, angling in two dimensions
can do wonders for a recording
room, especially for the ceiling. If you
are considering something like this, a
copy of Philip Newell’s Recording
Room Dimensions
If you are going to be constructing your
room from scratch, one important thing to
keep in mind is that the worst sounding
rooms are always going to be ones whose
three dimensions are all divisible by the
same number, for example 24’x36’x12’. If
you already have a situation like this, rest
assured it is not the “end of the world.”
Treating your room with Auralex products
can take care of many of your room’s
A 226.00 in 162.00 in 84.00 in 574cm 411cm 213cm
B 218.75 in 182.75 in 90.00 in 556cm 464cm 229cm
C 253.50 in 182.50 in 96.00 in 644cm 464cm 244cm
D 252.00 in 209.00 in 102.00 in 640cm 531cm 259cm
E 293.75 in 206.25 in 108.00 in 746cm 524cm 274cm
F 301.00 in 217.75 in 114.00 in 765cm 553cm 290cm
G 302.50 in 218.50 in 120.00 in 768cm 555cm 305cm
H 342.75 in 243.25 in 126.00 in 871cm 618cm 320cm
J 359.00 in 257.50 in 132.00 in 912cm 654cm 335cm
K 343.50 in 285.75 in 138.00 in 872cm 726cm 351cm
L 354.25 in 296.75 in 144.00 in 900cm 754cm 366cm
Five Vocal Booth Room Dimension Suggestions (Courtesy
of Auralex)
66.25 in
84.00 in 203cm 168cm 213cm
A 79.75 in
72.25 in
87.00 in 215cm 184cm 221cm
B 84.50 in
68.50 in
90.00 in 222cm 174cm 229cm
C 87.25 in
69.75 in
93.00 in 224cm 177cm 236cm
D 88.25 in
74.00 in
96.00 in 239cm 188cm 244cm
E 94.00 in
Note: Dimensions are not ranked - they are in order according to
increasing ceiling height.
Note: Ratios are deliberately omitted since a good ratio for one
Now, if you are in a situation where you can
set of dimensions does not necessarily constitute a universally
design a room with good dimensional ratios,
"ideal" ratio.
there is something you should keep in mind.
The ratios that are often published are a very small sampling of the many, many good room ratios
and room dimensions you can implement. As an illustration of this, our Engineers recently wrote a
program that would rank ideal room dimensions based on two of the most popular criteria. Table 5.1
shows a small sampling of the results we’ve obtained so far. Should you have some dimensions, or
ranges of dimensions you are considering you can either contact us and we will help you decide, or
you can look check out the forum where many useful tools are housed (and where
many of the world’s experts in home studio design, construction, etc. help people just like you every
The Acoustics 101 Room
In previous versions of, you may have seen a rough sketch (plan view) of a room
with angled walls and roughly drawn in acoustical treatments. Well, by very popular demand, we’ve
taken that very general room concept and turned it into a PDF you can actually use. So if you are
building from scratch and desire to build the best stereo mixing room you can without getting drowned
by formulas and equations, take a look at the official Acoustics 101 Room PDF (see APPENDIX 2).
When built as outlined elsewhere on this site, this shape – which is loosely based on dozens of
million dollar rooms – will be about the best you could ever hope for if you are the type who likes a
little controlled liveness in your control room.
Should you prefer a more neutral room – perhaps something along the lines of a “Hidley Room” or a
“Non-environment,” you can simply replace the T’Fusors shown on the rear wall with thick absorption,
such as Venus Bass Traps. For more information on the “Non-environment” design, we would
recommend Philip Newell’s Recording Studio Design.
5.1 Mixing Rooms
If you have been reading all the ink in the trades lately regarding top engineers mixing for release in
5.1 channel surround format and are considering making the move to a surround mixing setup
yourself, there are some acoustic issues that must be addressed. Acoustically treating a control room
to yield an accurate surround-mixing environment can be quite different from treating a "typical"
control room in which stereo monitoring is performed.
In treating a stereo mix environment, we introduce large amounts of absorption at the front of the
room to kill early reflections so the engineer hears only the direct sound coming straight to his or her
ears from the monitors. We sporadically absorb the rear half of the room’s side walls and sometimes
ceiling to allow the rear of the room to breathe. We introduce broadband diffusion devices into the
rear wall and rear ceiling area of the room to spread out the sound energy in the room without killing
it, thus imparting a sense of space and envelopment at the mix position. The contribution from
diffusion on the rear wall is not detrimental to the imaging and direct sound perceived at the mix
position because the diffused sound should be arriving at the mixer’s/listener’s ears delayed enough
in relation to the direct sound. Thus, the brain/ear mechanism is not confused by the diffused sound.
(The minimum path length from loudspeaker to rear wall to listener is typically on the order of about
16’-20’. This means that if your front-to-back dimension is not at least 10’ to 12’, you are probably not
getting your money’s worth with any diffusion on the rear wall.)
Conversely, a 5.1 channel surround mixing environment requires that absorption be used to yield
early reflection control at the room boundaries near all five surround loudspeakers, not just the front
two used in a stereo mixing environment. Whereas 5.1 channel listening and mixing environments
allow you to hear much greater detail in the program material, especially with regard to reverberation
and other ambience, diffusion is not usually appropriate in these environments because it would
make you think there was more ambience on your tracks than there really was and negate much of
the painstaking work that went into the surround mix. Obviously this is not desirable. [Note that if you
are setting up a room for 5.1 playback only (no mixing), you might benefit from diffusion at the rear of
the room if you are using dipole surrounds.]
For the mixing environment, we advise room surface absorption all around (including the ceiling), a
reflective floor and we also encourage the user to strongly consider beefing up the absorption
materials used so that even, broadband absorption is achieved. Symmetry is very important when
implementing the acoustic treatments in a room in which accurate 5.1 mixing or listening is to be
performed. Extra low frequency absorption is advised due to the LFE (the “.1”) channel’s extreme
bass output capabilities.
For more information on setting up surround mixing environments, we highly recommend either of the
following articles:
Stop! You’re Surrounded by Philip Newell, Audio Media, May 2001
Surround Listening Environments – Acoustics Count by John Storyk, Pro Audio Review, June
Other Resources
If you would like to look through some plans (beside the Acoustics 101 Room) for building your
recording studio, we would suggest the SAE Reference Materials site. Simply click on the
“Studio Plans” link on the left side of the page.
If you are serious about designing and building a full-blown facility from the ground up (and you
have a BIG budget), Auralex can assist! We can provide a full studio facility design working in
conjunction with the Russ Berger Design Group and would be happy to prepare a scope of
work and fee proposal for you. Contact us for more information.
General Resources
Auralex already has a wealth of case-specific product application information available through the
following resources:
The Auralexian – Monthly installments of specific problems we have helped our customers address
using Auralex products.
Featured Industry Profiles – Some unique applications of products and some high-profile customers
with whom we have worked.
Night Club Isolation
The Situation
A blues club with a residential apartment upstairs.
The Structure
Concrete walls, concrete floor, concrete ceiling with suspended ceiling tiles 18" down. While the client
noticed less-than-ideal sound in the club, the main problem he wished to combat was the
structureborne transmission of sound to the apartment upstairs.
Our responses were as follows:
Roll out 6" unfaced insulation over the top of the suspended ceiling grid, then roll out a layer of
SheetBlok over the top of the insulation (or at least back each ceiling tile with SheetBlok). Alternately,
roll out 12" of insulation over the top of the suspended ceiling if it is determined that the ceiling cannot
support the additional weight of SheetBlok even with reinforcement. Seal the juncture where the
rolled out SheetBlok meets the structure by using the aforementioned tape.
Pull back the carpet and pad on the stage. Pull up the layer of plywood over the framing members
(joists). Insulate between the joists with 6" of insulation to cut down the reflected sound under the
stage. Line the bottoms of the joists with SheetBlok to isolate the stage from the structural concrete
floor. Install a layer of SheetBlok on the floor of the stage itself, or at least a layer of ¾" MDF and then
a layer of ¾" particle board, cross-seamed. Then lay the padding and carpet back down. If the pad is
not 6# rebond, replace it with this type or ComfortWear-200, which will offer 5-7dB of additional sound
isolation. The stage should be kept as physically separate from the structure as possible. For
maximum control, build new walls adjacent to the existing walls as outlined earlier or at least add
additional layers of gypsum board to the existing walls with a layer of SheetBlok then a layer of 5/8"
gypsum board. The club owner was unwilling to do either of these, so we recommended he apply 4”
Studiofoam, realizing that it would alleviate at least some of the low frequency sound that is offending
the apartment upstairs.
Garage Isolation and Treatment
The Situation
A one-car 13’x19’ garage; carpeted floor; ⅝" gypsum board walls; no windows; 1 36" solid-core door;
acoustical tile ceiling at 8’ height. The room is used to teach guitar and rehearse with guitar, bass,
drums and drum machine.
The Problem
Excessive slap echo and reverb along with excessive low-end buildup due to drum kit being located
in one corner. Owner not overly worried about sound transmission to/from the outside, but would like
some additional transmission control.
Our responses were as follows:
Roll out unfaced insulation over the top
of the suspended ceiling tiles, thus
increasing transmission loss through
the ceiling while adding low frequency
control to the room.
Treat all four vertical corners with
LENRD Bass Traps.
Treat the walls with 2" Studiofoam,
preferably cut into 2’x2’ panels and
applied in a staggered checkerboard
pattern with space between panels,
easily adapted so no two parallel walls
are mirror-images of each other. This
method yields improved absorption and
diffusion without costing any more
money. Coverage minimum for a room
of this size and with this intended
usage is 45%; 60-75% is more
The customer originally thought he wanted to purchase Venus Bass Traps and 12" CornerFills for all
four (4) wall/ceiling junctures, but we recommended LENRDs instead because of his room’s size. We
advised 2" Studiofoam for the walls instead of 4" because the slap echo and excessive reverb dictate
more coverage, not thicker foam. If the budget allowed, 4" Studiofoam would be a welcome
When adding layers of building materials or SheetBlok to adjacent walls, put a layer on one
wall, then the other, then one wall, then the other instead of putting all one wall’s layers on at
once then moving to the other wall. As shown in Figure 5.1, this gives sound waves a tougher
path to snake through at the corners. Be sure to caulk (with StopGap) or mud all joints before
adding the next layer.
People often ask about using plywood in the construction of their studio. Plywood is not as
wise a choice as gypsum board or MDF because the latter are considerably denser and in
many cases cheaper.
One easy way to achieve better sound isolation from neighboring spaces is to enlist the help of
the people who are likely to be in those spaces when you’re recording. To help alert them that
you’re laying down tracks, why not install a remote ON AIR light or some other warning system
outside your studio so they can easily know when to keep their activity and/or noise level
down? All it takes is a light switch in your studio, some cable and a fixture. For a few bucks you
can probably gain quite a bit of extra quiet.
Never smoke in your control room because it is bad for you and your equipment, to say
nothing of the way it lowers your gear’s resale value.
Vacuum frequently, being careful to avoid static electricity.
Cover your mixer with a clean towel when not in use.
If you use a computer, turn it on after your power amps, etc., and turn it off before your power
amps, etc. and make sure you turn your monitor (and peripherals) off first and on last.
World’s best and cheapest computer monitor anti-static cleaning wipes: Used fabric softener
dryer sheets.
Cheap "talkback" control room-to-studio communication tool: Wireless intercoms (available at
Radio Shack) or a baby monitor.
To keep your air as clean as outdoor air after a thunderstorm, check out an ionizer for your
studio. People the world over have testified that not only do ionizers clean the air, they tend to
make people feel better. They are great for allergies and getting rid of particulate matter in the
Be sure to check out these two valuable links for more great tips and information:
o Auralex General Acoustics FAQ Page
o Monthly Acoustology archives (scroll down on the Auralex Literature Page)
If after reading Acoustics 101 you are dazed and confused, feel free to fill out our Personalized Room
Analysis Form (Adobe Acrobat PDF), available here or from your favorite dealer. E-mail or fax it back
to us and our product application specialists will respond (generally within 2-3 business days) with
their suggestions for your room.
If you would prefer a quick, online analysis, rectangular rooms up to about 20’x20’x10’ can be run
through our Interactive Kit Calculator, which will respond with a basic analysis and some suggestions
for Roominators Kits.
We have compiled many great links on acoustics here. If you have some you’d like to share, feel free
to contact us!
Online Forums
Auralex forum on
Auralex forum AV:Talk
Acoustics discussion on
Professional Organizations
Acoustical Society of America (ASA)
Audio Engineering Society (AES)
Custom Electronic Design and Installation Association (CEDIA)
International Communications Industries Association (InfoCOMM)
Institute for Noise Control Engineering (INCE)
International Music Products Association (NAMM)
National Systems Contractors Association (NSCA)
Percussive Arts Society (PASIC)
Synergetic Audio Concepts (Syn-Aud-Con)
Professional Design Assistance
Russ Berger Design Group
National Council of Acoustical Consultants (NCAC)
Consultants page on
Acoustical Prediction, Test and Measurement
CARA software for small room modeling from Rhintek
ULYSSES software for large room modeling from IFBSoft
Audio Toolbox™ from TerraSonde
ETF software from AcoustiSoft
Cool Corporate (non-Auralex) Stuff
The British Broadcasting Company (BBC) now has many of their acoustical research papers
available for download from the BBC R&D page.
Genelec white papers
Rane Library includes an excellent online audio dictionary, the Pro Audio Reference
Rosebrand is the company we turn to for our heavy curtain needs.
Sound Construction and Supply is the place to go for Iso-Box™, as well as all of you studio
furniture needs.
Cool People
Eric Desart, one of the world’s best acoustical minds, has created and assembled some
wonderful tools available for limited download from his website.
Bob Golds has assembled and discussed the absorption coefficients of a bunch of different
David Griesinger of Lexicon fame has his own technical website – very cool stuff.
• is Kent Morris’ site. Kent is a world-renowned expert in church systems
Bruce Richardson has written a review of Auralex products and services for here.
Keith Yates is a leading home theater design expert. Of particular interest are Keith’s articles
on myriad home theater sound topics.
Other Cool Stuff
Some cool standing wave/mode animations
The Gypsum Board Construction Handbook is a must-have for anyone building a studio…and
now it’s available free electronically!
Rane Professional Audio Reference Home
Pro Audio Reference
Last Updated August 1, 2004
[Site updated semiannually; usually February and August]
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Copyright 2004 by the Rane Corporation. All rights reserved. This publication in whole or in part may not be
reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical,
photocopying, recording or otherwise, without the prior written permission of the Rane Corporation unless such copying is
expressly permitted by federal copyright law.
Trademarks and tradenames are those of their respective owners. No definition in this document is to be regarded as
affecting the validity of any trademark. Any word included within this document is not an expression of Rane
Corporation's opinion as to whether or not it is subject to proprietary rights.
Rane Corporation believes the information in this publication is accurate as of its publication date; such information is
subject to change without notice. Rane Corporation is not responsible for any inadvertent errors. Rane Corporation has
obtained information contained in this work from sources believed to be reliable. However, neither Rane nor its authors
guarantees the accuracy or completeness of any information published herein and neither Rane nor its authors shall be
responsible for any errors, omissions, or damages arising out of use of this information. This work is made available with
the understanding that Rane and its authors are supplying information but are not attempting to render engineering or other
professional services. If such services are required, the assistance of an appropriate professional should be sought.
Rane Corporation gratefully acknowledges the Houghton Mifflin Company publication, The American Heritage
Dictionary of the English Language, Fourth Edition (credit shown "AHD"), and the IEEE publication, IEEE 100: The
Authoritative Dictionary of IEEE Standards Terms, Seventh Edition (credit shown "IEEE"), in the preparation of this
revision of Rane's Professional Audio Reference. (1 of 2) [10/3/04 12:27:19 AM]
Rane Professional Audio Reference Home
Compiled by Dennis A. Bohn, CTO, Rane Corporation. Write me (2 of 2) [10/3/04 12:27:19 AM]
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Pro Audio Reference
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0 See zero.
0 dBFS See decibel
0 dBm See decibel
0 dBr See decibel
0 dB-SPL See decibel
0 dBu See decibel
0 dBV See decibel
1/3-octave See one-third octave
1/4" TRS or 1/4" TS See connectors
1/f noise See flicker noise
1 The other half of all the stored knowledge in a computer; compare with zero. And, surprisingly, not a
prime number. A prime number is defined to be a natural number (i.e., a positive whole number) greater
than one which has exactly two different factors: one and itself.
3D See 3D sound
3-dB down point or -3 dB point See passband
+4 dBu See decibel
5.1 See 5.1 surround sound (1 of 4) [10/3/04 12:28:32 AM]
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6.1 Extended version of 5.1 surround sound (called Dolby Digital ES but this isn't official) where one
rear channel is added to the basic 5.1 group resulting in: left-front, center, right-front, left-surround, rightsurround, rear and subwoofer.
6s or 6 Sigma See Six Sigma
7.1 Extended version of 5.1 surround sound (called Dolby Digital EX, this is official) where left and right
rear channels are added to the basic 5.1 group resulting in: left-front, center, right-front, left-surround,
right-surround, left-rear, right-rear and subwoofer.
10Base-T or 100Base-T or 1000Base-T or 1000Base-F See Ethernet
-10 dBV See decibel
10.2 Somewhat tongue-in-check term created by Tom Holman (of THX fame) for his experimental (but
impressive) surround system based on 5.1 surround sound, but with twelve channels. See Kim Wilson
"Tomlinson Holman's Next Experiment" for speaker locations and description.
12:00 Syndrome The phenomenon affecting too many pro audio sound people whereby they feel
obligated to set all rotary controls "straight up," or within an 11:00 to 1:00 aperture, thereby destroying all
the product designer's good work to provide them with a large range of adjustment to cover
16 2/3 rpm Phonograph recording speed obtained using a half-speed converter on a 33 1/3 rpm machine,
used for special recording purposes, but never a standard.
21-gun salute See 21-gun salute
24/96 Data conversion using 24-bits quantization at 96 kHz sampling rate.
24/192 Data conversion using 24-bits quantization at 192 kHz sampling rate.
33 1/3 rpm record The standardized phonograph recording speed selected for the long-play record.
Warren Rex Isom explains the reasons in his article, "Before the Fine Groove and Stereo Record and
Other Innovations," published in the Journal of the Audio Engineering Society, October/November, 1977,
Vol. 25, No. 10/11, pp. 815-820. The quick answer is that Western Electric synchronized motion pictures
with phonograph records in 1925. A reel of 35-mm film runs for 11 minutes. A record needed to play the
same length of time, which was 3.66 times longer than the 3-minute 10-inch 78-rpm standard. After
considering optimum needle groove velocity and diameter, while shooting for something approximately
half of the 78-rpm standard that would easily lock to the 60 Hz line, 33 1/3 rpm was the answer (see Isom (2 of 4) [10/3/04 12:28:32 AM]
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for the exact details).
42V PowerNet See 42V PowerNet
45 rpm record The standardized phonograph recording speed selected for the single song record. Warren
Rex Isom explains the reasons in his article, "Before the Fine Groove and Stereo Record and Other
Innovations," published in the Journal of the Audio Engineering Society, October/November, 1977, Vol.
25, No. 10/11, pp. 815-820. One popular belief is that 45 rpm was selected because 78 - 33 = 45. While
not too far off, it was a more practical engineering matter that created the ballpark number, and perhaps
that mathematical nicety determined the exact number. Once marketing decided on a 7-inch disc with 5
1/2 minutes of playing time, and knowing the groove details and cutter restrictions, the speed satisfying
these conditions is 45 rpm.
62 miles Space is defined as being this distance above the earth.
70-volt line See constant-voltage
78 rpm record First standardized phonograph recording speed (exact speed was 78.26 rpm for 60 Hz
power and 77.92 rpm for 50 Hz power). The reason for 78 rpm is explained by Warren Rex Isom in his
article, "Before the Fine Groove and Stereo Record and Other Innovations," published in the Journal of
the Audio Engineering Society, October/November, 1977, Vol. 25, No. 10/11, pp. 815-820. The short
summary is that the first machines were handcranked and a comfortable speed was heartbeat rate -between 60 and 90 per minute. (Interestingly, the same cadence as marching bands and the same speed
recommended for handcranked farm equipment.) When it became time to standardize, Victor machines
operated at 78 rpm, while competing Edison machines used 80 rpm, but Victor was the predominate sales
leader so it was picked for maximum compatibility. The exact speed of 78.26 rpm came from a simple
gearing reason: For a 60 Hz synchronous motor, and a simple worm-gear drive, a ratio of 46 to 1 turned
the table at 78.26 rpm and synchronized with the line.
232 See: RS-232
485 See: RS-485
802.3af See: PoE
802.11 See: Wi-Fi
1394 See: IEEE-1394
2182 kHz Maritime international voice distress/safety/calling frequency. (3 of 4) [10/3/04 12:28:33 AM]
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4810 The number engraved on the nib of every Montblanc fountain pen, representing the height of the
Mont Blanc mountain in meters. Mont Blanc in the French Alps is the highest mountain in Europe and
the company's namesake: a symbol for the
highest quality standards reached with the products named after it.
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Pro Audio Reference
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AAC (Advanced Audio Coding) Shortened name for the MPEG-2 Advanced Audio Coding specification,
declared an international standard by MPEG in April 1997; however, now the term is used also to refer to
MPEG-4 advanced audio coding.
A&R (artists and repertory) Historically the record industry term for the department or person that acts as the
go-between the artist and the record label. Their job is to select and sign the performers to the label, decide
what songs they will record, and select who will work with the artists in the production arranging and
performance of the material for the recording of master tapes. These details vary a lot from label to label. For a
good discussion on how the A&R world is changing see Rap Coalition's Intelligence Program by Wendy Day.
A Barking Dog The Weblog of Dave Stevens, the founder of LAB and cofounder of ProSoundWeb.
abbreviation 1. The act or product of shortening. 2. A shortened form of a word or phrase used chiefly in
writing to represent the complete form, such as Mass. for Massachusetts or USMC for United States Marine
Corps. (AHD) Compare with acronym and initialism.
absorption To absorb is to receive (an impulse) without echo or recoil: a fabric that absorbs sound; a bumper
that absorbs impact; therefore absorption is the act or process of absorbing. The absorption of sound is the
process by which sound energy is diminished when passing through a medium or when striking a surface, i.e.,
sound is attenuated by absorption. (AHD) The physical mechanism is usually the conversion of sound into
heat, i.e. sound molecules lose energy upon striking the material's atoms, which become agitated, which we
characterized as warmth; thus, absorption is literally the changing of sound energy to heat. A material's ability
to absorb sound is quantified by its absorption coefficient, whose value ranges between 0 (total reflection) and
1 (total absorption), and just to keep things interesting, varies with sound frequency and the angle of incidence.
See Siegfried Linkwitz's Acoustic absorption and acoustic resistors; contrast with isolation.
A/B testing (or A-B testing) A comparison testing methodology where a first test, A, is compared against a
second test, B.
ABX testing (aka ABX double-blind comparator) A system controller for audio component comparison
testing where the listener hears sound-A, sound-B, and sound-X. The listener must make a determination as to
whether X is A or B. The subject may go back to A and B as often and for as long as necessary to make a
determination. The listener knows that A and B are different and that X is either A or B, so there is always a
correct answer. The "double-blind" part comes from neither the tester nor the listener (can be the same) knows
what source is A, B or X, only the controller knows, which is downloaded after the test is complete to
determine the results. First invented in 1977 by Arnold Krueger and Bern Muller (of the famous Southeastern (1 of 19) [10/3/04 12:28:47 AM]
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Michigan Woofer and Tweeter Marching Society or SMWTMS), later refined and marketed by David Clark and
his ABX Company. [For complete details see David L. Clark, "High-Resolution Subjective Testing Using a
Double-Blind Comparator", J. Audio Eng. Soc., Vol. 30 No. 5, May 1982, pp. 330-338.]
AC-3 (audio coding 3) Dolby's digital audio data compression algorithm adopted for HDTV transmission and
used in DVDs, laserdiscs and CDs for 5.1 multichannel home theater use. See: Dolby Digital. Competes with
DTS Consumer. The terms AC-1 and AC-2 are other versions developed by Dolby for different applications.
Academy curve The name of the standard mono optical track that has been around since the beginning of
sound for film. Standardized in 1938, it has improved (very) slightly over the years. Also known as the N
(normal) curve the response is flat 100 Hz-1.6 kHz, and is down 7 dB at 40 Hz, 10 dB at 5 kHz and 18 dB at 8
kHz. This drastic "dumping" of the high-end was to hide the high-frequency "frying" and "crackling" noise
inherent in early film sound production. Compare with X curve
Accelerated-SlopeTM A trademark of Rane Corporation used to describe their family of patented tone control
technologies that produce steeper slopes than normal, thus allowing boost/cut of high and low frequencies
without disturbing the critical midband frequencies.
accommodation Said to be the most misspelled word in American writing (two "c"s and two "m"s).
accordion "An instrument in harmony with the sentiments of an assassin." -- Ambrose Bierce.
acoustic distortion Term coined by Dr. Peter D'Antonio, founder of RPG Diffusor Systems, for the interaction
between the room, the loudspeaker, and the listener.
acoustic echo canceller See: echo canceller
acoustic feedback The phenomenon where the sound from a loudspeaker is picked up by the microphone
feeding it, and re-amplified out the same loudspeaker only to return to the same microphone to be re-amplified
again, and so on. Each time the signal becomes larger until the system runs away and rings or feeds back on
itself producing the all-too-common scream or squeal found in sound systems. These buildups occur at
particular frequencies called feedback frequencies.
acoustic lens 1. Loudspeakers. An acoustic lens focuses sound in much the same way that an optical lens
focuses light. Snell's law describes the refraction of sound as it passes through an interface between two
materials of differing sound speed. A high frequency loudspeaker mechanical acoustic lens provides the
appropriate apparatus to spread a single point sound source into a parallel wave front. Additional information
available from B&O, and JBL. 2. Ultrasonography. A lens (often electromagnetic) used to focus or diverge a
sound beam.
acoustic lobe See: Linkwitz-Riley crossover
acoustics 1. Hearing; from the Greek akouein: to hear. 2. The study of sound. (2 of 19) [10/3/04 12:28:47 AM]
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acoustic treatments There are only three classic (physical) tools available for the acoustician to treat a room:
absorbers, reflectors and diffusers. Absorbers attenuated sound; reflectors redirect sound, and diffusers
(hopefully) uniformly distribute sound. Or put another way, these tools change the temporal, spectra and spatial
qualities of the sound. Additionally, with today's advanced digital audio tools, all of these elements can be
electronically manipulated.
acquisition time The time required for a sample-and-hold (S/H) circuit to capture an input analog value;
specifically, the time for the S/H output to approximately equal its input.
ACR (attenuation to crosstalk ratio) Category wiring. The ratio of attenuation and crosstalk in a cable, i.e., a
measure of the difference between the received signal magnitude vs. the leaked crosstalk signal.
acronym A word formed from the first letters of a name, such as laser for light amplification by stimulated
emission of radiation, or by combining initial letters or parts of a series of words, such as radar for radio
detecting and ranging. The requirement of forming a word is what distinguishes an acronym from an
abbreviation (or initialism as it is also called). Thus modem [modulator-demodulator] is an acronym, and AES
[Audio Engineering Society] is an abbreviation or initialism. Compare with portmanteau word [Unsubstantiated
rumor has it that the word "acronym" itself is an acronym, created from the phrase "abbreviating by cropping
remainders off names to yield meaning" -- but it has never been confirmed.] (Thanks MR.)
active crossfader A device found in DJ mixers used to crossfade between two music sources. An active design
uses the potentiometer to send a control voltage to some type of voltage-controlled device that controls the
audio, while in a passive design the audio appears on the potentiometer itself. Active designs are more robust
and offer greater reliability over passive ones. See Evolution of the DJ Mixer Crossfader by Rane's ace DJ
mixer designer, Rick Jeffs, for additional details.
active crossover A loudspeaker crossover requiring a power supply to operate. Usually rack-mounted as a
separate unit, active crossovers require individual power amplifiers for each output frequency band. Available
in configurations known as stereo 2-way, mono 3-way, and so on. A stereo 2-way crossover is a two-channel
unit that divides the incoming signal into two segments, labeled Low and High outputs (biamped). A mono 3way unit is a single channel device with three outputs, labeled Low, Mid and High (triamped). In this case, the
user sets two frequencies: the Low-to-Mid, and the Mid-to-High crossover points. Up to stereo 5-way
configurations exist for very elaborate systems. See: passive crossover and RaneNote: Signal Processing
active equalizer A variable equalizer requiring a power supply to operate. Available in many different
configurations and designs. Favored for low cost, small size, light weight, loading indifference, good isolation
(high input and low output impedances), gain availability (signal boosting possible), and line-driving ability.
Disliked for increased noise performance, limited dynamic range, reduced reliability, and RFI susceptibility;
however, used everywhere. See RaneNote: Operator Adjustable Equalizers
ActiveX A Microsoft developed software technology released in 1996. ActiveX, formerly called OLE (Object (3 of 19) [10/3/04 12:28:47 AM]
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Linking and Embedding), is loosely based on the Component Object Model (COM), but provides substantially
different services to developers. An ActiveX component is a unit of executable code (such as an .exe file) that
follows the Active X specification for providing objects. This technology allows programmers to assemble
reusable software components into applications and services. However, component software development using
ActiveX technology should not be confused with Object-Oriented Programming (OOP). OOP is concerned with
creating objects, while ActiveX is concerned with making objects work together. Simply stated, ActiveX is a
technology that lets a program (the ActiveX component or control) interact with other programs over a network
(e.g., the Internet), regardless of the language in which they were written. ActiveX components can do similar
things as Java beans, but they are quite different. Java is a programming language, while ActiveX controls can
be written in any language (e.g., Visual Basic, C, C++, even Java), Also ActiveX runs in a variety of
applications, while Java beans usually run only in Web browsers. ActiveX controls are of concern to the pro
audio community, because this is the technology that allows designers of computer-controlled sound systems to
create common front-end software control panels that will operate different manufacturer's units, without
having to know anything about their internal code or algorithms. Each ActiveX control is made up of
properties, values associated with the control which might include such things as level settings and meter
readings, and events, which tell the computer something significant has happened, such as a switch closer or
clip detection. ActiveX allows the manufacturer to create an object that fully describes a device, while hiding
the implementation details, such as protocol from the programmer. By hiding the communication details, there
is no longer a need for different manufacturer's devices to agree on protocol. This lack of a protocol standard
means that cooperation between manufacturers is not required. It allows each manufacturer to choose the best
protocol for their devices. See RaneNote: Controlling Audio Systems with ActiveX .
adaptive delta modulation (ADM) A variation of delta modulation in which the step size may vary from
sample to sample.
ADAT (Alesis Digital Audio Tape) Digital tape recording system developed by Alesis, and since licensed to
Fostex & Panasonic, putting 8-tracks of 16-bit, 44.1 kHz digital audio on S-VHS tape.
ADAT ODI (optical digital interface) See ADAT Optical.
ADAT Optical Alesis's proprietary multichannel optical (fiber optic) digital interface specification for their
family of ADAT modular digital multitrack recorders. This standard describes transmission of 8-channels of
digital audio data through a single fiber optic cable.
ADC (or A/D, analog-to-digital converter) The electronic component which converts the instantaneous value
of an analog input signal to a digital word (represented as a binary number) for digital signal processing. The
ADC is the first link in the digital chain of signal processing. See data converter bits See RaneNote: Digital
Dharma of Audio A/D Converters
ADJA (American Disc Jockey Association) An organization of professional disc jockeys that promotes ethical
behavior, industry standards and continuing education for its members.
administratium See: "Administratium" [No technical glossary is complete without this term. Supporting
evidence is given by the fact that it took the GoogleTM search engine just 0.25 second to return 2,150 versions (4 of 19) [10/3/04 12:28:47 AM]
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located on the Web. Among these, it is credited to more than six authors, a hundred different research centers,
universities and corporations, and is dated from the 1980s to the 1990s, but there is compelling evidence that it
dates back to the '60s. Anyone who can prove who really wrote this classic piece of humor and when, please
write me. Thanks.]
ADPCM (adaptive differential pulse code modulation) A very fast data compression algorithm based on the
differences occurring between two samples.
ADR (automatic dialog replacement) Film postproduction term used to indicate the act and location where
dialogue that is not taped during production or that needs to be redone is recorded and synchronized to the
picture. Usually the name of the room where this occurs, containing a studio with a screen, TV monitors,
microphones, control area, console and loudspeakers.
Advanced Audio Coding See: AAC
AES (Audio Engineering Society) Founded in 1948, the largest professional organization for electronic
engineers and all others actively involved in audio engineering. Primarily concerned with education and
AES17 low-pass filter The common name given to the low-pass filter defined by AES standard method for
digital audio engineering -- Measurement of digital audio equipment AES17-1998, used to limit the measuring
bandwidth. The rather daunting specifications call for a filter with a passband response of 10 Hz to 20 kHz,
±0.1 dB and a stopband attenuation greater than 60 dB at 24 kHz.
AES24 A developing AES standard for sound systems using computer networks to control audio equipment.
Formerly called "SC-10" (after the working group's subcommittee number), the title for AES24-1-1999 (the
first part to be published) is Application Protocol for Controlling and Monitoring Audio Devices via Digital
Data Networks -- Part 1: Principles, Formats, and Basic Procedures. The complete standard is broken down
into several parts issued separately. The second part, in the proposed draft stage, is titled -- Part 2: Data Types,
Constants, and Class Structure. The remaining two parts are in process.
AES3 interface (The interface formerly known as AES/EBU). The serial transmission format standardized for
professional digital audio signals (AES3-1992 AES Recommended Practice for Digital Audio Engineering Serial transmission format for two-channel linearly represented digital audio data). A specification using time
division multiplex for data, and balanced line drivers to transmit two channels of digital audio data on a single
twisted-pair cable using 3-pin (XLR) connectors. Issued as ANSI S4.40-1985 by the American National
Standards Institute. In addition, information document AES-3id is available describing the transmission of
AES3 formatted data by unbalanced coaxial cable. Transmission by fiber optic cable is under discussion. The
consumer version is referred to as S/PDIF. See RaneNote: Interfacing AES3 and S/PDIF
AES/EBU interface See AES3
AFL Abbreviation for after fade listen, a term used on recording consoles and mixers, referring to a signal (5 of 19) [10/3/04 12:28:47 AM]
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taken after the main channel fader; hence this sampling point tracks the main fader level. Also referred to as
post fade solo, but since PFL already meant pre fade, AFL was adopted to prevent confusion. Got it? Compare
with PFL and APL.
AIFF (audio interchange file format) Defined by Apple Computer in 1988, it provides a standard for storing
monaural and multichannel sampled sounds at a variety of sample rates and widths.
air raid siren See: Chrysler Air Raid Siren
album covers See: Steinweiss, Alex
aleatoric Music. Using or consisting of sounds to be chosen by the performer or left to chance; indeterminate.
From aleatory meaning dependent on chance, luck, or an uncertain outcome. Of or characterized by gambling.
algorithm A structured set of instructions and operations tailored to accomplish a signal processing task. For
example, a fast Fourier transform (FFT), or a finite impulse response (FIR) filter are common DSP algorithms.
aliasing The problem of unwanted frequencies created when sampling a signal of a frequency higher than half
the sampling rate. See: Nyquist frequency. Also see RaneNote: Digital Dharma of Audio A/D Converters
all-pass filter A filter that provides only phase shift or phase delay without appreciably changing the magnitude
ALMA (American Loudspeaker Manufacturers Association) Founded in 1964, an international trade
association for companies that design, manufacture, sell, and/or test loudspeakers, loudspeaker components and
loudspeaker systems.
ambience 1. Acoustics. A perceptual sense of space (Blesser). The acoustic qualities of a listening space
(White). 2. Psychoacoustics The special atmosphere or mood created by a particular environment; also spelled
ambiance (AHD). Contrast with reverberation
Ambisonics A British-developed surround sound system designed to reproduce a true three-dimensional sound
field. Based on the late Michael Gerzon's (1945-1996) ( Oxford University) famous theoretical foundations,
Ambisonics delivers what the ill-fated quadraphonics of the '70s promised but could not. Requiring two or
more transmission channels (encoded inputs) and four or more decoded output loudspeakers, it is not a simple
system; nor is the problem of reproducing 3-dimensional sound. Yet with only an encoded stereo input pair and
just four decoded reproducing channels, Ambisonics accurately reproduces a complete 360-degree horizontal
sound field around the listener. With the addition of more input channels and more reproducing loudspeakers, it
can develop a true spherical listening shell. As good as it is, a mass market for Ambisonics has never developed
due to several factors. First, the actual recording requires a special tetrahedron array of four microphones: three
to measure left-right, front-back and up-down sound pressure levels, while the fourth measures the overall
pressure level. All these microphones must occupy the same point in space as much as possible. So far, only (6 of 19) [10/3/04 12:28:47 AM]
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one manufacturer (first Calrec, bought by AMS, bought by Siemens, sold, now Soundfield) is known to make
such an array. Next, a professional Ambisonics encoding unit is required to matrix these four mic signals
together to form two or more channels before mastering or broadcast begins. Finally, the consumer must have
an Ambisonics decoder, in addition to at least four channels of playback equipment.
AMI-C (Automotive Multimedia Interface Collaboration) "An organization of motor vehicle manufacturers
worldwide created to facilitate the development, promotion and standardization of electronic gateways to
connect automotive multimedia, telematics and other electronic devices to their motor vehicles."
AMPAS (Academy of Motion Picture Arts & Sciences) Created in 1927, a professional honorary organization
composed of over 6,000 motion picture craftsmen and women. Think Oscars®.
ampere Abbr. I, also A. 1. A unit of electric current in the International standard meter-kilogram-second (mks)
system. It is the steady current that when flowing in straight parallel wires of infinite length and negligible cross
section, separated by a distance of one meter in free space, produces a force between the wires of 2E-7 newtons
per meter of length. 2. A unit in the International System specified as one International coulomb per second and
equal to 0.999835 ampere. [After André Marie Ampère.] (AHD)
Ampère, André Marie (1775-1836) French physicist and mathematician who formulated Ampère's law, a
mathematical description of the magnetic field produced by a current-carrying conductor. (AHD)
amplifier An electronic device used to increase an electrical signal. The signal may be voltage, current or both
(power). Preamplifier is the name applied to the first amplifier in the audio chain, accepting inputs from
microphones, or other transducers, and low output sources (CD players, tape recorders, turntables, etc.). The
preamplifier increases the input signals from mic-level, for instance, to line-level. Power amplifier is the name
applied to the last amplifier in the audio chain, used to increase the line-level signals to whatever is necessary to
drive the loudspeakers to the loudness required. See amplifier classes.
amplifier classes Audio power amplifiers were originally classified according to the relationship between the
output voltage swing and the input voltage swing; thus it was primarily the design of the output stage that
defined each class. Classification was based on the amount of time the output devices operate during one
complete cycle of signal swing. Classes were also defined in terms of output bias current [the amount of current
flowing in the output devices with no applied signal]. For discussion purposes (with the exception of class A),
assume a simple output stage consisting of two complementary devices (one positive polarity and one negative
polarity) using tubes (valves) or any type of transistor (bipolar, MOSFET, JFET, IGFET, IGBT, etc.).
[Historical Notes marked "GRS" provided by Gerald R. Stanley, Senior V.P. of Research, Crown International,
Inc., designer of the famous Crown DC-300, inventor of the Crown K Series switchmode amplifier line and
holder of 20 U.S. Patents, with three pending as of 2003.]
[GRS on amplifiers: "At first there were no amplifiers as the very thought of amplification had yet to enter the
vocabulary of electronics (another word which had yet to be birthed!). The invention of a three-terminaled
device (DeForest Audion U.S. patent 841,386 or later triode) was the invention in 1906 of a more sensitive (7 of 19) [10/3/04 12:28:47 AM]
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radio detector and not an element for an amplifier.
By 1912 the triode had become both a vacuum tube and an amplifier (multiple names can be attached to this
collective achievement). The oscillator also dates to 1912 giving proof to the saying "When you set out to make
an amplifier you get an oscillator and when you attempt to make an oscillator you get an amplifier."]
[GRS on amplifier classes: "Originally it was adequate to distinguish amplifier classes only by the conduction
angles of the control elements (tubes or valves). More recently it has been necessary to add distinctions that
relate to topology, degrees of conduction and control methods to be able to determine class."]
Class A operation is where both devices conduct continuously for the entire cycle of signal
swing, or the bias current flows in the output devices at all times. The key ingredient of class A
operation is that both devices are always on. There is no condition where one or the other is
turned off. Because of this, class A amplifiers in reality are not complementary designs. They are
single-ended designs with only one type polarity output devices. They may have "bottom side"
transistors but these are operated as fixed current sources, not amplifying devices. Consequently
class A is the most inefficient of all power amplifier designs, averaging only around 20%
(meaning you draw about 5 times as much power from the source as you deliver to the load.)
Thus class A amplifiers are large, heavy and run very hot. All this is due to the amplifier
constantly operating at full power. The positive effect of all this is that class A designs are
inherently the most linear, with the least amount of distortion. [Much mystique and confusion
surrounds the term class A. Many mistakenly think it means circuitry comprised of discrete
components (as opposed to integrated circuits). Such is not the case. A great many integrated
circuits incorporate class A designs, while just as many discrete component circuits do not use
class A designs.]
[GRS Historical Note: "Class A - The most basic of operating modes saw both single-ended and
push-pull embodiments by 1913. The first known use of push-pull appears in a patent of E.F.W.
Alexanderson of GE U.S. 1,173,079 filed in 1913. While Alexanderson would have been aware of
other levels of biasing his push-pull stage, such as classes B and C, he would have only been able
to produce a useful result with a tuned stage such as a transmitter where resonant filtering would
have managed the distortion problem. Negative feedback is not understood in 1913 to be able to
cope with distortion problems."]
Class B operation is the opposite of class A. Both output devices are never allowed to be on at
the same time, or the bias is set so that current flow in a specific output device is zero when not
stimulated with an input signal, i.e., the current in a specific output flows for one half cycle. Thus
each output device is on for exactly one half of a complete sinusoidal signal cycle. Due to this
operation, class B designs show high efficiency but poor linearity around the crossover region.
This is due to the time it takes to turn one device off and the other device on, which translates
into extreme crossover distortion. Thus restricting class B designs to power consumption critical
applications, e.g., battery operated equipment, such as 2-way radio and other communications
[GRS Historical Note: "Class B - This class has no obvious inventor, but it does have its master (8 of 19) [10/3/04 12:28:47 AM]
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and perfector. Loy Barton working for RCA developed tube designs and biasing methods to
manage the open loop distortion of class B push-pull power stages. His IRE paper in 1931 titled
"High Output Power from Relatively Small Tubes" is a landmark in the history of class B.
Technically he only used class AB but the distinction was not in the language. Class AB is a later
and probably unnecessary class fabrication."]
Class AB operation is the intermediate case. Here both devices are allowed to be on at the same
time (like in class A), but just barely. The output bias is set so that current flows in a specific
output device appreciably more than a half cycle but less than the entire cycle. That is, only a
small amount of current is allowed to flow through both devices, unlike the complete load current
of class A designs, but enough to keep each device operating so they respond instantly to input
voltage demand s. Thus the inherent non-linearity of class B designs is eliminated, without the
gross inefficiencies of the class A design. It is this combination of good efficiency (around 50%)
with excellent linearity that makes class AB the most popular audio amplifier design.
Class AB1 & AB2 Subdivisions of Class AB developed for vacuum tube design.
These subsets primarily describe grid current behavior: Class AB1 has no current
flowing into the grid of the tube, and Class AB2 has some current flowing into the
grid. Class AB1 operates closer to Class A, while Class AB2 operates closer to
Class B. Most bipolar solid-state amplifiers would be classified as Class AB2,
while power JFET designs mimic Class AB1.
Class AB plus B design involves two pairs of output devices: one pair operates class AB while
the other (slave) pair operates class B.
[GRS Historical Note: "Class AB+B is a term that I'd coined and is intended to be very
descriptive but is not truly worthy of its own class. The Crown DC-300 was the first to use this
mode of operation in 1968."]
Class BD Invented by Robert B. Herbert in 1971 U.S. patent 3,585,517 and improved on by Neil
Edward Walker as disclosed in his 1971 U.S. patent 3,629,616. Both patents are concerned with
improving original class D design efficiencies by using various bridge connections and
cancellation techniques. And most recently more improvements are claimed by inventors James
C. Strickland & Carlos A. Castrejon in their U.S. patent 6,097,249 assigned to Rockford
Corporation in 2000 for their Fosgate-brand automotive amplifier.
[GRS comments: "This is a class designation that would best be forgotten. It has been applied to
multiple modulation schemes on a class D derived full-bridge. This is perhaps the most
reinvented class design in recent history with "filter-less amplifiers" and other such things. An
interleave of two class D full-bridge is what we actually have here, and it is a good improvement
to an interleave of one class D full-bridge. However an interleave of four is actually possible on
a full-bridge if one uses class I design."]
Class C use is restricted to the broadcast industry for radio frequency (RF) transmission. Its (9 of 19) [10/3/04 12:28:47 AM]
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operation is characterized by turning on one device at a time for less than one half cycle. In
essence, each output device is pulsed-on for some percentage of the half cycle, instead of
operating continuously for the entire half cycle. This makes for an extremely efficient design
capable of enormous output power. It is the magic of RF tuned circuits (flywheel effect) that
overcomes the distortion create d by class C pulsed operation.
Class D operation is switching, hence the term switching power amplifier. Here the output
devices are rapidly switched on and off at least twice for each cycle (Sampling Theorem).
Theoretically since the output devices are either completely on or completely off they do not
dissipate any power. If a device is on there is a large amount of current flowing through it, but all
the voltage is across the load, so the power dissipated by the device is zero (found by multiplying
the voltage across the device [zero] times the current flowing through the device [big], so 0 x big
= 0); and when the device is off, the voltage is large, but the current is zero so you get the same
answer. Consequently class D operation is theoretically 100% efficient, but this requires zero onimpedance switches with infinitely fast switching times -- a product we're still waiting for;
meanwhile designs do exist with true efficiencies approaching 90%. [Historical note: the original
use of the term "Class D" referred to switching amplifiers that employed a resonant circuit at the
output to remove the harmonics of the switching frequency. Today's use is much closer to the
original "Class S" designs.
[GRS Historical Note: "Class D is a subset of all possible switch-mode amplifier topologies that
is typified by use of the half-bridge (totem-pole) output stage that has two interconnected
switches operating in time alternation. The paradigm is that of Loy Barton's class B, but uses the
statistics of conduction angle to produce amplification (PWM). There are many subclasses within
class D that describe the origins of the modulation. Class D is at least as old as 1954 when
Bright patented a solid-state full-bridge servo amplifier U.S. 2,821,639."]
Class E operation involves amplifiers designed for rectangular input pulses, not sinusoidal audio
waveforms. The output load is a tuned circuit, with the output voltage resembling a damped
single pulse. Normally Class E employs a single transistor driven to act as a switch.
The following terms, while generally agreed upon, are not considered "official"
Class F Also known by such terms as "biharmonic," "polyharmonic," "Class DC," "single-ended
Class D," "High-efficiency Class C," and "multiresonator." Another example of a tuned power
amplifier, whereby the load is a tuned resonant circuit. One of the differences here is the circuit is
tuned for one or more harmonic frequencies as well as the carrier frequency. See References:
Krauss, et al. for complete details.
[GRS Historical Note: "Classes E and F are distinguished by their resonant topology and not
conduction angle else we would class them with C. A good reference to these is found in the many
patents of Nathan Sokal. Also class S which is very old (1929-1930) has similar applications
(resonant RF)."] (10 of 19) [10/3/04 12:28:47 AM]
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Class G operation involves changing the power supply voltage from a lower level to a higher
level when larger output swings are required. There have been several ways to do this. The
simplest involves a single class AB output stage that is connected to two power supply rails by a
diode, or a transistor switch. The design is such that for most musical program material, the
output stage is connected to the lower supply voltage, and automatically switches to the higher
rails for large signal peaks [thus the nickname rail-switcher]. Another approach uses two class
AB output stages, each connected to a different power supply voltage, with the magnitude of the
input signal determining the signal path. Using two power supplies improves efficiency enough
to allow significantly more power for a given size and weight. Class G is becoming common for
pro audio designs.
[Historical note: Hitachi is credited with popularizing class G designs with their 1977
Dynaharmony HMA 8300 power amplifier, however it is shown much older by GRS: "Class G - I
have been searching for the proper inventor of this class, but have not been able to find a
reference older than 1965 when I first encountered it in a college text "Handbook of Basic
Transistor Circuits and Measurements" by Thornton et al., SEEC vol. 7. The method is
introduced without references or fanfare. One is led to believe that it was common knowledge in
1965 and earlier. This is not the first known use of extended quasi-linear methods (beyond class
B), as there is a dual found in Fisher U.S. 2,379,513 from 1942."]
Class H operation takes the class G design one step further and actually modulates the higher
power supply voltage by the input signal. This allows the power supply to track the audio input
and provide just enough voltage for optimum operation of the output devices [thus the nickname
rail-tracker or tracking power amplifier]. The efficiency of class H is comparable to class G
[Historical note: Soundcraftsmen is credited with popularizing class H designs with their 1977
Vari-proportional MA5002 power amplifier, however like class H above GRS finds precedence:
"Class H - The apparent inventor of class-H in full-blown multi-level form was Manuel Kramer
of NASA in 1964 U.S. patent 3,319,175. Class H optimally applied to a full-bridge was invented
in 1987 (Stanley) U.S. 4,788,452. Classes G and H are all members of a class of amplifiers that
has articulated rail voltages to improve the efficiency of class B power stages. Examples are
available of tracking using binarily weighted segments, (Stanley) U.S. 5,045,990. Continuously
variable tracking with switch-mode PWM appears to have been first done by Hamada in 1976
U.S. 4,054,843. The ultimate rail tracker using interleaved technology is found in (Stanley) U.S.
5,513,094. Only with interleave is the converter fast enough to meet the needs of full-bandwidth
audio and yet have low switching losses."]
Class I operation invented and named by Gerald R. Stanley for amplifiers based on his patent
U.S. 5,657,219 covering opposed current converters. [GRS explains: The "I" of the class is short
for "interleave" as this is the only four-quadrant converter known that uses two switches yet has
an interleave number of 2 in the terminology of interleave. When used with fixed-frequency
natural two-sided PWM it forms a theoretically optimum converter having the least
unnecessary/undesirable PWM spectra. A good reference is found in the IEEE Transactions on
Power Electronics Vol. 14, No. 2, March 1999, pages 372-380."] (11 of 19) [10/3/04 12:28:47 AM]
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Class J operation is the category/name suggested by Gerald R. Stanley for amplifiers that
combine class B and class D where converters act in parallel to drive the load. [GRS elaborates:
"There are serious problems with the power efficiency of these products when processing fast
signals into arbitrary loads. The class B stage is used to actively remove the ripple of the class D
stage and other distortion problems that plague class D. No solution is offered for the MOSFET
CSOA (current safe operating area) problem of class D. To solve that problem it would be
to parallel a class I and class B amplifier but this would be without merit as the class I amplifier
generally does not need the class B amplifier to meet fidelity requirements."]
Class S First invented in 1932, this technique is used for both amplification and amplitude
modulation. Similar to Class D except the rectangular PWM voltage waveform is applied to a
low-pass filter that allows only the slowly varying dc or average voltage component to appear
across the load. Essentially this is what is termed "Class D" today. See References: Krauss for
[Final GRS Amplifier Historical Note: "All of our amplifier classes have thrived under a very
important invention, without which most would have floundered. That invention is, of course,
negative feedback. Harold Black in 1927 changed our world forever while riding to work on the
Lackawanna Ferry. (See U.S. patent 2,102,671.) Harold Black did not stop there however, he
also in 1953 wrote the text "Modulation Theory" which we today use to understand the
fundamentals of PWM. In 1935, Terman, in his now famous "Fundamentals of Radio" handbook,
wrote that it was good that class B was only used in places like radio stations as there needed to
be an engineer on duty full time to keep the bias tweaked to where the distortion was acceptable.
Thanks go to Harold Black for changing all that and leading us into the next century of
amplifier dummy load Modeling a real world loudspeaker for power amplifier testing purposes has been
studied for years, resulting in many circuit possibilities. An article compiled and edited by Tomi Engdahl
entitled "Speaker Impedance" is an excellent summary of the results. He gives a complete (and complex)
solution to the loudspeaker dummy load question. However you can get excellent results with a simplified
version developed by Michael Rollins, Sr. Design Engineer, Rane Corporation, appearing below. The series
resistor and inductor model the loudspeaker voice coil's DC resistance and inductance, while the parallel
inductor and capacitor simulate the mechanical components of suspension compliance and cone mass
respectively. The values shown work well for most power amplifier measurements.
RS = 6 ohms (aluminum body power resistor bolted to heatsink; (12 of 19) [10/3/04 12:28:47 AM]
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power rating twice max testing watts)
LS = 0.33 mH (air core inductor; wire sized for max current)
LP = 20 mH (air core inductor; wire sized for max current)
CP = 1000 µF (100 V, or maximum expected peak voltage;
paralleling two 500 µF caps may be smaller, cheaper)
amplitude 1. Greatness of size; magnitude. 2. Physics. The maximum absolute value of a periodically varying
quantity. 3. Mathematics. a. The maximum absolute value of a periodic curve measured along its vertical axis.
b. The angle made with the positive horizontal axis by the vector representation of a complex number. 4.
Electronics. The maximum absolute value reached by a voltage or current waveform. (AHD)
amplitude-frequency response See frequency response.
analog A real world physical quantity or data characterized by being continuously variable (rather than making
discrete jumps), and can be as precise as the available measuring technique.
anechoic Literally, without echo, used to describe specially designed rooms, anechoic chambers, built to
emulate a free sound field, by absorbing practically all the sound field.
angstrom A unit of length equal to one-tenth of a nanometer -- used for measuring the wavelengths of light.
anode 1. A positively charged electrode. 2. In a vacuum tube, it is the plate electrode. 3. In a forward-biased
semiconductor diode it is the positive terminal. Contrast with cathode.
ANSI (pronounced "ann-see") (American National Standards Institute) A private organization that develops
and publishes standards for voluntary use in the U.S.A.
Antheil, George (1900-1959) US Composer, specializing in film music, who described himself as "America's
bad boy of music."
Among Antheil's early avant-garde pieces, none caused a greater sensation than his Balet
mécanique, scored for automobile horns, airplane propeller, fire siren, ten grand pianos, and
other instruments. When it was performed at Carnegie Hall in 1924, a concertgoer near the
orchestra could stand no more than a few minutes of the racket. Tying his handkerchief to his
cane, he raised the white flag in surrender. [Bartlett's Book of Anecdotes]
anti-aliasing filter A low-pass filter used at the input of digital audio converters to attenuate frequencies above
the half-sampling frequency to prevent aliasing.
anti-imaging filter A low-pass filter used at the output of digital audio converters to attenuate frequencies
above the half-sampling frequency to eliminate image spectra present at multiples of the sampling frequency. (13 of 19) [10/3/04 12:28:47 AM]
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APA (Audio Publishers Association) The online resource center designed for audiobook listeners and industry
apparent power The result of multiplying the rms value of the voltage by the rms value of the current in an
electronic circuit. It is expressed in watts (W) for resistive loads and in volt-amperes (VA) for reactive loads.
It's the amount of power the casual observer thinks is available (hence, apparent), but because of power factor
may not be -- the real power is usually less. See power factor .
APL (after processing listen) A mixing console term and feature that allows post-processing monitoring of the
signal. Compare with: AFL and PFL.
ARM (advanced RISC machines) The name for a microprocessor group formed from Acorn, backed by Apple,
VLSI Technology and Nippon Investment and Finance, in 1990. Acorn Computer was the parent company set
up by Dr. Hermann Hauser and Dr. Chris Curry in 1979 to make personal computers, but now enjoys its biggest
success selling intellectual property around their proprietary RISC computer, called ARM, which originally
stood for Acorn RISC Machines.
Armstrong, Edwin Howard (1890-1954) American radio engineer and inventor of regenerative feedback, FM
(frequency modulation) and the superheterodyne receiver.
ARRL (American Radio Relay League) The national association for amateur radio.
articulated line arrays See: line arrays
ASA (Acoustical Society of America) Founded in 1929, the oldest organization for scientist and professional
acousticians and others engaged in acoustical design, research and education.
ASCII (pronounced "ask-ee") (American Standard Code for Information Interchange) An ANSI standard
data transmission code consisting of seven information bits, used to code 128 letters, numbers, and special
characters. Many systems now use an 8-bit binary code, called ASCII-8, in which 256 symbols are represented
(for example, IBM's "extended ASCII").
ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc.) An
international organization organized for the purpose of advancing the arts and sciences of heating, ventilation,
air-conditioning and refrigeration for the public's benefit through research, standards writing, continuing
education and publications.
ASIC (application-specific integrated circuit) A large-scale integrated circuit whose function is determined by
the final mask layer for a particular application or group of applications; for example, an IC that does all the
functions of a modem.
ASIO (audio stream input/output) A multichannel audio transfer protocol developed by Steinberg in 1997, for
audio/MIDI sequencing applications, allowing access to the multichannel capabilities of sound cards. (14 of 19) [10/3/04 12:28:47 AM]
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ASPEC (adaptive spectral perceptual entropy coding) A bit rate reduction standard for high quality audio.
Jointly developed by AT&T Bell Labs, Thomson, the Fraunhofer Society and CNET. Characterized by high
degrees of compression to allow audio transmission on ISDN.
asymmetrical (non-reciprocal) response Term used to describe the comparative shapes of the boost/cut
curves for variable equalizers. The cut curves do not mirror the boost curves, but instead are quite narrow,
intended to act as notch filters.
asynchronous A transmission process where the signal is transmitted without any fixed timing relationship
between one word and the next (and the timing relationship is recovered from the data stream).
A-taper See potentiometer
ATM (asynchronous transfer mode) networking An extremely fast networking technology already found on
many disk editors (Avid, Sonic Solutions, Studio Audio, etc.) and predicted to infiltrate homes within the
coming decade. ATM specifies the protocol (i.e., the order and sequence) of the digital information on the
network, but not the physical means of transmission (e.g., fiber optic, twisted-pair, etc.). The protocol controls
how the entire network is run and maintained.
atmospheric pressure Pressure caused by the weight of the atmosphere. At sea level it has a mean value of one
atmosphere but reduces with increasing altitude. [AHD] See: 0 dB-SPL
attack Music. The beginning or manner of beginning a piece, passage, or tone. [AHD] A measure of how long
it takes for the beginning to peak. Contrast with decay. Audio Compressors. How fast the gain is turned down
once the signal exceeds the threshold setting. Contrast with release.
attenuation to crosstalk ratio See: ACR.
attenuator or attenuator pad Electronics. A passive network that reduces the voltage (or power; see usage
note under gain) level of a signal with negligible distortion, but with insertion loss. Often a purely resistive
network, although any combination of inductors, resistors and capacitors are possible, a pad may also provide
impedance matching. [Compare with fader and crossfader. More details available in an excellent article by Rick
Chinn, "Pads 101" appearing in the Syn-Aud-Con Newsletter, Vol. 32, No. 2 Spring 2004, pp. 8-11.]
Pads are referred to by the topology of the network formed, with the two most common being an
L-pad and a T-pad:
L-pad A two-leg network shaped like an inverted, backward letter "L". It usually consists of two
resistors that are fixed or adjustable. A true variable L-pad consists of two variable
potentiometers that are ganged (tied) together. The ganged sections work to provide either a
constant input or a constant output impedance regardless of the attenuation setting. Since modern
analog audio electronic circuits consist of stages characterized by very high input and very low
output impedances, the term is now broaden to include all L-shaped networks without the (15 of 19) [10/3/04 12:28:47 AM]
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requirement of providing constant impedance to the source or load. Volume and level controls are
common examples.
T-pad A three-leg network shaped like the letter "T". It usually consists of three resistors that are
fixed or adjustable. A true variable T-pad consists of two or three variable potentiometers that are
ganged (tied) together. The ganged sections work to provide either a constant input or a constant
output impedance regardless of the attenuation setting. Since modern analog audio electronic
circuits consist of stages characterized by very high input and very low output impedances, the
term is now broaden to include all T-shaped networks without the requirement of providing
constant impedance to the source or load.
Balanced L-pad A balanced version of the above L-pad, the following is for general purpose
audio, recommended by the IEC, exact and nearest 1% values shown.
audio 1. Of or relating to humanly audible sound, i.e., audio is all the sounds that humans hear (approximately
20 Hz - 20 kHz). 2. a. Of or relating to the broadcasting or reception of sound. b. Of or relating to high-fidelity
sound reproduction. [Audio traveling through air is vibrations, or cycles of alternating pressure zones.
Rarefaction follows each cycle of compression, which produces a wave.] (AHD)
Audio Annals A pro audio industry sponsored history of audio technology -- wonderful and worthwhile
audio books See: Pro Audio Reference Books for books used to create this site.
audio bridge A communications bridge that allows multiple duplex connections over 4-wire telephone
connections. Well designed audio bridges, such as Rane's ECB 6 do not connect inputs to their own outputs,
thus avoiding feedback. See mix-minus.
audio compression See: digital audio data compression (16 of 19) [10/3/04 12:28:47 AM]
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audio connectors See connectors.
Audio Courses Interesting website, its an online audio production school but with lots of useful (and free)
audio levels See: levels and decibels.
Audio magazine (1947-2000) America's first and longest running audio magazine. Its demise after 53 years of
continuous publication leaves a huge void in the consumer audio world. Gone is the last great rational voice,
lost amidst the pseudoscientific din dominating high-end audio. An audio warrior is dead and we are lessened.
audion Dr. Lee De Forest's name for his 1906 invention of the triode (three-element vacuum tube), building
upon Sir John Ambrose Fleming's thermionic diode, based on the Edison effect. De Forest credits his assistant,
C.D. Babcock for the name.
audion piano The first vacuum tube instrument in 1915, invented by Dr. Lee De Forest.
audio snake See: snake.
audio taper See potentiometer
Audio Timeline A most fascinating audio development timeline created by three esteemed AES members,
Jerry Bruck, Al Grundy and Irv Joel, as part of the 50th anniversary of the AES.
audio websites A truly astonishing and remarkable list of audio related websites compiled daily by Steve
Ekblad. Also see Audio & Hi-Fi Page, an equally astonishing and remarkable list of audio related websites
compiled by Tomi Engdahl. And for a refreshingly rational voice on hot audio topics check out Rod Elliott's
site, particularly his get-rich-quick scheme for exploiting the gullible regarding burning-in audio cables.
[Absolutely brilliant.]
auditory filter Term used to describe the concept of critical bands. Analogous to a bandpass filter with a
rounded top ("rounded-exponential" after Patterson and Moore, 1986). The filter is slightly asymmetric, being
wider on the low-frequency side.
aural hallucinations See: clairaudient.
Aureal 3D (A3D) Proprietary 3D sound technology first developed by Crystal River Engineering, which
became the advanced technology subsidiary of Aureal Semiconductor, alas, now defunct. Aureal 3D made
many claims. At one time their website stated that "since we can hear sounds three dimensionally in the real
world by using two ears, it must be possible to create sounds from two speakers that have the same effect" ...
well ... NO ... it's pretty rhetoric, but flawed logic. Our two ears receive sound coming from sources located in (17 of 19) [10/3/04 12:28:47 AM]
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every possible direction, and from that information process three-dimensional location -- that is not the
problem. The problem is how to make our two ears receive sound from sources located in only two directions,
and trick them into hearing three dimensionally -- that is the problem. Aureal claimed to have solved this
problem, but didn't stay in business long enough for anyone to find out.
auricle See: pinna.
authoring DVD, CD or CD-ROM. A term used to indicate more than writing, now used to include all the
processes necessary (designing, creating & editing) to add information of any sort onto a DVD, CD or CDROM primarily providing search and retrieval features.
autoformer Autoformer is short for autotransformer, or self-transformer, from the definition of auto-. An
autotransformer is one that self-magnetizes to produce the transformer voltage, it does this by not having a true
secondary, i.e., there is only one winding with one part acting as the primary and the other part acting as the
secondary, but there is no second winding, and no air gap, and thus no true isolation between the primary and
secondary. Therefore an autotransformer is a transformer in which part of one winding is common to both the
primary and the secondary circuits associated with that winding. For this reason, autotransformers are not the
preferred choice for professional audio use because in addition to the transformed voltage (usually 70.7 V in the
U.S. & 100 V elsewhere) you want true isolation. However, they are common because they are cheaper to make
since you don't have to wind a separate primary and secondary.
automatic mic mixer A specialized mixer optimized for solving the problems of multiple live microphones
operating together as a system, such as found in boardrooms, classrooms, courtrooms, church systems, etc. An
automatic mic mixer controls the live microphones by turning up (on) mics when someone is talking, and
turning down (off) mics that are not used, thus it is a voice-activated, real-time process, without an operator,
hence, automatic. An automatic mic mixer must adapt to changing background noise conditions. Further it must
control the additive effect of multiple mics being on at the same time (see NOM). If one mic is on at maximum
gain, opening up another one may cause acoustic feedback, so an automatic mixer must also control the system
gain to prevent feedback or excessive noise pickup. Dan Dugan patented the first automatic mic mixer and is
recognized as the father of this technology. A final problem that automatic mixers solve is maintaining a natural
ambience from the room. This is especially critical in recording and broadcasting. A good automatic mixer
must make rapid and dramatic changes in the gains of the input channels while maintaining the sonic illusion
that nothing is happening at all.
aux fed subs, or aux fed subwoofers A live sound technique becoming popular when subwoofers are used
with the FOH system. It is claimed that a properly configured and operated aux fed subwoofer system better
maintains gain structure and crossover relationships. See Tom Young's article at ProSoundweb, "A Detailed
Explanation Of The Aux Fed Subwoofer Technique"
AVD (advanced video disk) A Chinese proposed alternative to the DVD standard to avoid paying what they
consider exorbitant royalties. This threatened standard would apply to DVD-like players sold only in China.
Members of the China Audio Industry Association (CAIA) say the spec could be published in late 2001 if the
DVD royalty issue remains unsettled. (18 of 19) [10/3/04 12:28:47 AM]
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average power See apparent power
A-weighting See weighting filters
AWG (American wire gauge) A specification for non-ferrous (e.g., copper, aluminum, gold, silver, etc.) wire
diameter. [Note, for example, that this means that 14 gauge galvanized steel wire & 14 gauge cooper wire have
different diameters.] Also known as Brown and Sharp (B&S) wire gauge, after J.R. Brown who devised the
system in 1857 (I have been unsuccessful in finding out what Sharpe's role was). For more detail, see Douglas
Brooks' "How to Gauge Traces." Many tables exist on the Internet; e.g., see Alpha. The British standard is
called SWG standing for Standard wire gauge, also called Imperial wire gauge. Compare with AWG here.
axe Musical instrument, usually a guitar.
azimuth 1. The horizontal angular distance from a reference direction, usually the northern point of the
horizon, to the point where a vertical circle through a celestial body intersects the horizon, usually measured
clockwise. Sometimes the southern point is used as the reference direction, and the measurement is made
clockwise through 360°. 2. The horizontal angle of the observer's bearing in surveying, measured clockwise
from a referent direction, as from the north, or from a referent celestial body, usually Polaris. 3. The lateral
deviation of a projectile or bomb. (AHD)
azure noise See noise color
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babbling tributary In LAN technology, a workstation that constantly sends meaningless messages.
babel Loud, confused, or disagreeable sound that stresses confusion of vocal sounds arising from
simultaneous utterance and random mixture of languages. After Babel, the biblical city (now thought to
be Babylon) in Shinar where God confounded a presumptuous attempt to build a tower into heaven by
confusing the language of its builders into many mutually incomprehensible languages. [AHD]
back-EMF (back-electromotive force) See also EMF. Literally, back-voltage, is a phenomena found in
all moving-coil electromagnetic systems, but for audio is most often used with respect to loudspeaker
operation. This term describes the action where, after the signal stops, the speaker cone continues moving,
causing the voice coil to move through the magnetic field (now acting like a microphone), creating a new
voltage that tries to drive the cable back to the power amplifier's output. If the loudspeaker is allowed to
do this, the cone flops around like a dying fish. It does not sound good. The only way to stop back-emf is
to make the loudspeaker "see" a dead short, i.e., zero ohms looking backward, or as close to it as possible.
See: damping factor
background music Officially music without lyrics and not performed by the original artist, used as an
alternative to silence. Contrast with foreground music.
backward masking See: temporal masking
baffle Loudspeakers. In its simplest form, the main speaker mounting board in a cabinet, whose primary
purpose is to separate the front and rear sound waves, from here it becomes a very complex subject.
baking Sound Recording. The name for the process required for old analog tapes where they must be put
into an oven and “baked” to remove moisture and prevent the oxide from shedding onto the tape heads.
balance control A control found most commonly on professional and consumer stereo preamplifiers,
used to change the relative loudness (power) between the left and right channels. Attenuating the opposite
channel makes one channel (apparently) louder. This is most often done (in analog designs) with a dual
potentiometer with an "M-N taper." An M-N taper consists of a "shorted" output for the first 50% of
travel and then a linear taper for the last 50% of travel, operating oppositely for each channel. Therefore,
with the control in its center detent position, there is no attenuation of either channel. Rotating it away
from the center position causes one channel to be attenuated, while having no effect on the other channel, (1 of 14) [10/3/04 12:28:59 AM]
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and vice-versa. Contrast with pan and crossfade controls.
balanced line The IEEE dictionary defines a balanced circuit as "a circuit in which two branches are
electrically alike and symmetrical with respect to a common reference point, usually ground." This is the
essence of a balanced interconnect. Namely, that two lines are driven equally and oppositely with respect
to ground. Normally this also implies that the receiving circuits have matching impedances. Exactly
matching impedances is preferred for it provides the best common mode rejection. Balances lines are the
preferred method (for hum free) interconnecting of sound systems using a shielded twisted-pair. Because
of its superior noise immunity, balanced lines also find use in interconnecting data signals, e.g., RS-422,
and digital audio, e.g., AES/EBU. The principal behind balanced lines is that the signal is transmitted over
one wire and received back on another wire. The shield does not carry any information, thus it is free to
function as a true shield, but must be earth grounded at each end to be successful. (For a detailed tutorial
on proper grounding practices, see RaneNote: Sound System Interconnection) [Long Answer: To
understand why balanced lines are so successful, first examine a balanced, or differential (equivalent
term) output stage, and then an input stage: A differential output stage simultaneously drives two lines,
one positive and one negative. The voltage difference between these two wires is the audio signal. The
two signals form an envelope that rides the wires to the balanced input stage. Note that the audio signal
exists uniquely between these two lines -- not between them and ground. The complete circuit path travels
down on the positive line and back on the negative line. Ground is not needed to transmit the signal -- this
is the essence and power of balanced lines. Ground is used only for shielding and safety purposes.
Conversely, an unbalanced line is one that transmits the audio signal between one wire and ground. The
circuit path is down the wire and back through the shield cable connected to ground. Ground is the return
path; the circuit does not work without it. A balanced (or differential) input stage extracts the difference
between the two input lines, and that, of course, is the desired audio signal. It receives the envelope sent
down the cable by the differential output. This circuit's shining virtue is its great noise rejection ability. It
has what is called great common-mode rejection. The concept here relies on induced noise showing up
equally (or common) on each wire. It is mainly due to EMI (electromagnetic interference: passing through
or near magnetic fields), RFI (radio frequency interference: strong broadcast signals), noisy ground
references, or a combination of all three. The best balanced line designs have exactly equal impedance
from each line relative to ground, guaranteeing equal noise susceptibility. Since the balanced input stage
amplifies only the difference between the lines, it rejects everything else (noise) that is common to the
ballistics See: meter ballistics
balun (balanced-unbalanced) A jargon term originally popularized by radio engineers referring to the
balanced to unbalanced transformer used to interface with the radio antenna. Today, expanded to refer to
any interface (usually a transformer) between balanced and unbalanced lines or circuitry; may also
provide impedance transformation, as 300 ohm balanced to 75 ohm unbalanced, or vice versa. Another
popular use is in transitioning between balanced twisted-pair and an unbalanced coaxial cable.
banana jack or banana plug See: connectors. (2 of 14) [10/3/04 12:28:59 AM]
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band-limiting filters A low-pass and a high-pass filter in series, acting together to restrict (limit) the
overall bandwidth of a system.
bandpass filter A filter that has a finite passband, neither of the cutoff frequencies being zero or infinite.
The bandpass frequencies are normally associated with frequencies that define the half power points, i.e.
the -3 dB points. See Figure 1 of RaneNote: Constant-Q Graphic Equalizers
bandwidth Abbr. BW 1. Electronic filters The numerical difference between the upper and lower -3 dB
points of a band of audio frequencies. Used to figure the Q, or quality factor, for a filter. See Figure 1 of
RaneNote: Constant-Q Graphic Equalizers; also download "Bandwidth vs. Q Calculator" as a zipped
Microsoft Excel spreadsheet in the Rane Library. 2. Telecommunications The size of the communications
channel. In analog communications, bandwidth is measured in Hertz (Hz), while digital communications
measures bandwidth (data transfer rate) in bits per second. For example, an analog telephone channel has
a bandwidth of 4,000 Hz, while a digitally coded telephone channel has a bandwidth of 64
kilobits/second. See RaneNote: Audio Specifications
banjo "I can see fiddling around with a banjo, but how do you banjo around with a fiddle?" -- Duncan
Purney [from Barber]
bar A unit of pressure equal to one million dynes per square centimeter. (Yeah, I know, you expected
some wiseacre response, but you ain't gonna get it.)
Bara, Theda (1890-1955) Anagram of "Arab Death," used as a pseudonym by the Cincinnati-born,
Hollywood actress Theodosia Goodman in the 1920s, who became the first woman movie star.
Baroque 1. Music: of, relating to, or characteristic of a style of composition that flourished in Europe
from about 1600 to 1750, marked by chromaticism, strict forms, and elaborate ornamentation. (AHD) 2.
When you are out of Monet. (Thanks JF and I'll never tell.)
barrelhouse Style of boogie piano playing. (Decharne)
barrier strips Same as terminal strips, see connectors.
baseband A transmission medium with capacity for one channel only. Typically found in local area
networks (LANs). In baseband LANs, the entire bandwidth, or capacity, of the cable is used to transmit a
single digital signal. Everything on that cable (transmitted or received) must use that one channel, which
is very fast, so each device needs only to use that high speed channel for only a little of the time.
Therefore all attached devices (printers, computers, databases) share by taking turns using the same cable.
Baseband as used in videoconferencing means audio and video signals are transmitted over separate
cables. Contrast with broadband. (3 of 14) [10/3/04 12:28:59 AM]
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baseband signaling Transmission of a digital or analog signal at its original frequencies; i.e., a signal in
its original form, not changed by modulation.
BASH® (Bridged Amplifier Switching Hybrid) Audio Amplifiers. The registered trademark of Indigo,
an OEM company, for their patented (U.S. 5,075,634 & U.S. 5,510,753) Class H power amplifier
technology that uses a fast-response, pulse-width modulated power supply and a linear Class AB
amplifier. BASH modules are found in many powered loudspeakers from Cambridge Audio to Pioneer to
bass management See Ken Kriesel's excellent write up on the M&K website; compare with LFE.
bass ratio (BR) Acoustics. An objective measure of sound "warmth." See Concert Hall Acoustics.
bass reflex Loudspeakers. A type of cabinet design featuring a "port" (a vent or opening of any shape) on
the baffle to allow the rear sound wave to exit (in phase -- that is the trick) with the front wave.Originally
a trademark of the Jensen Company in the 1930s. [White], this popular design is also called a vented
bathythermographAcoustics. A device unsed in underwater acoustics to measure water temperature at
different depths for the purpose of determining the velocity of speed in seawater. See: XBT
battle axe Musician slang for a trumpet. (Decharne)
baud rate (pronounced "bawd"; after Baudot Code named for the French telegrapher Emile Baudot, 18451903) The transmitted signaling speed, or keying rate of a modem. Often confused with bit rate. Bit rate
and baud rate are NOT synonymous and shall not be interchanged in usage. For example, one baud
equals one half dot cycle per second in Morse code, one bit per second in a train of binary signals, and
one 3-bit value per second in a train of signals each of which can assume one of 8 different states, and so
on - all brought to you by the magic of advanced coding techniques that allow more than one bit per baud.
Preferred usage is bit rate, with baud used only when the details of a modem are specified.
Baxandall tone controls The most common form of active bass and treble tone control circuit based
upon British engineer P.J. Baxandall's paper "Negative Feedback Tone Control -- Independent Variation
of Bass and Treble Without Switches," Wireless World, vol. 58, no. 10, October 1952, p. 402. The
Baxandall design is distinguished by having very low harmonic distortion due to the use of negative
BCD 1. (binary-coded decimal) Pertains to a number system where each decimal digit is separately
represented by a 4-bit binary code; for example, the decimal number 23 is represented as 0010 0011 (2 =
0010 and 3 = 0011, grouped together as shown), while in straight binary notation, 23 is represented as (4 of 14) [10/3/04 12:28:59 AM]
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10111. 2. (binary-coded digit) A digit of any number system that is represented as a fixed number of
binary digits; from the previous example, the decimal digit 23 is represented as 10111.
beamforming Popular buzz word in audio pick-ups for teleconferencing. Makes use of spatial filters and
arrays. Nice explanation by Greg Allen here and a teleconferencing demo by Koen Eneman here.
beat Physics. To cause a reference wave to combine with a second wave so that the frequency of the
second wave can be studied through time variations in the amplitude of the combination. [AHD]
beat frequency Equal to the absolute value of the difference in frequency of two waves beating together
(see "beat" above).
Beat Generation The story goes like this ...
In The Origins of the Beat Generation Jack Kerouac (1922-1969) recalled how he
borrowed the term that labeled an entire decade from a broken-down drug addict named
Herbert Huncke and how he then went on to use it himself. "John Clellon Holmes ... and I
were sitting around trying to think up the meaning of the Lost Generation and the
subsequent existentialism and I said, 'You know, this is really a beat generation': and he
leapt up and said, 'that's it, that's right.'" [Bartlett's Book of Anecdotes] See Generation X
Beat me Daddy, eight to the bar. Play some boogie-woogie for me. (The left-hand bass lines in typical
boogie-woogie piano feature a driving, eight-to-the-bar rhythm.) (Decharne)
bebop Modern jazz style developed by Charlie Parker, Dizzy Gillespie and others in the early 1940s.
Dizzy put out a single called "Bebop" in 1945 and also released "He Beeped When He Shoulda Bopped,"
in 1946. (Decharne) See: bop
Begun, Semi Joseph (1905-1995) Born in German, he immigrated to the U.S. in 1935 and pioneered
magnetic tape recording. He wrote the first book published on magnetic recording and invented many
recording products including the first consumer tape recorder as well as developing the technology that
gave birth to the Black Box flight data recorder. Subject of a fascinating book by Mark Clark.
bel Abbr. b, B Ten decibels. [After Alexander Graham Bell.] The Bel was the amount a signal dropped
in level over a one-mile distance of telephone wire. See: decibel
Belchfire® Series Term coined by Crown International for their mythical power amplifier, the BF6000SUX. Based on original research into the first principles of teramagnostriction quasar-quadrature, the
BF-6000SUX could have changed the design of all future power amps, but it didn't. In spite of Crown's
leap forward into the past of technical declination, the marketplace categorically stated that it did not want
6,000 watts per channel in only one rack space - in spite of its six-foot depth and 206 pounds weight. The (5 of 14) [10/3/04 12:28:59 AM]
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only known use of a BF-6000SUX was to drive the experimental Electro-Voice Rearaxial Softspeaker,
when Rane demoed their PI 14 Pseudoacoustic Infector using Jensen's JE-EP-ERs Multi-denomial
Transpedance Informer for coupling - but many consider that only hearsay.
Bell, Alexander Graham (1847-1922) Scottish-born American inventor of the telephone. The first
demonstration of electrical transmission of speech by his apparatus took place in 1876. Bell also invented
the audiometer, an early hearing aid, and improved the phonograph. (AHD)
belly fiddle Guitar. (Decharne)
benders or bending See: circuit-bending
Benten or Ben Zai Ten Japanese Deity. Goddess of music. The name of one of the Seven Gods of Good
Fortune, the goddess of music, art, happiness and love.
BeOS (Be operating system) An operating system (OS) developed by Be Incorporated in 1996, called the
first true "media OS," it is becoming very popular for Internet appliances, as well as software designed for
live performance venues.
BER (bit error ratio) (also called bit error rate) 1. The ratio of the number of erroneous bits divided by
the total number of bits transmitted, received, or processed over some stipulated period. 2. The number of
bits processed before an erroneous bit is found (e.g., 10E13), or the frequency of erroneous bits (e.g., 10E13).
Bessel crossover A type of crossover utilizing low-pass filter design characterized by having a linear
phase response (or maximally flat phase response), but also a monotonically decreasing passband
amplitude response (which means it starts rolling off at DC and continues throughout the passband).
Linear phase response (e.g., a linear plot of phase shift vs. frequency produces a straight line) results in
constant time-delay (all frequencies within the passband are delayed the same amount). Consequently the
value of linear phase is it reproduces a near-perfect step response, i.e., there is no overshoot or ringing
resulting from a sudden transition between signal levels. The drawback is a sluggish roll-off rate. For
example, for the same circuit complexity a Butterworth response rolls off nearly three times as fast. This
circuit is based upon Bessel polynomials; however, the filters whose network functions use these
polynomials are correctly called Thompson filters [W.E. Thomson, "Delay Networks Having Maximally
Flat Frequency Characteristics," Proc. IEEE, part 3, vol. 96. Nov 1949, pp. 487-490]. The fact that we do
not refer to these as Thompson crossovers demonstrates, once again, that we do not live in a fair world.
See Ray Miller, Bessel Filter Crossover and Its Relation to Other Types
biamp, biamplified, or biamplification Term used to refer to a 2-way active crossover where the audio
signal is split into two paths, and using separate power amplifier channels for each driver. (6 of 14) [10/3/04 12:28:59 AM]
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bipolar transistor Pertaining to a semiconductor technology in which transistors are built from
alternating layers of positively and negatively doped semiconductors material. [IEEE]
BICSI® (Building Industry Consulting Services, International) A telecommunications association that
is a worldwide resource for technical publications, training, conferences, and registration programs for
low-voltage cabling distribution design and installation.
BIEM (Bureau International des Sociétés Gérant les Droits d'Enregistrement et de Reproduction
Mécanique) An international organization representing mechanical rights societies found in most
countries. They license the reproduction of songs (including musical, literary and dramatic works). Their
members are composers, authors and publishers and their clients are record companies and other users of
recorded music. They also license the downloading of music via the Internet.
bifilar windings A term most often associated (in the pro audio industry) with audio transformer design
describing the winding technique of laying two wires side-by-side, providing essentially unity coupling,
thus reducing leakage inductance to negligible amounts. Literally two threads from Latin bi- two, and
filum thread.
bigit Very early contraction term for "binary digit," now obsolete. (Mentioned by Edmund C. Berkeley in
his book The Computer Revolution, Doubleday, 1962, page 234.) See: bit
bilinear transform A mathematical method used in the transformation of a continuous time (analog)
function into an equivalent discrete time (digital) function. Fundamentally important for the design of
digital filters. A bilinear transform ensures that a stable analog filter results in a stable digital filter, and it
exactly preserves the frequency-domain characteristics, albeit with frequency compression.
binary A condition in which there are two possible states; for example, the binary number system (base2) using the digits 0 and 1. See RaneNote: Digital Dharma of Audio A/D Converters
binary logarithm A logarithm based on the powers of 2 (aka base 2).
binaural recording or binaural sound Believe it or not, the groundwork was laid in the 1920s (no
kidding, and some claim even earlier) when the idea of placing two microphones in a dummy head was
first introduced as a source of loudspeaker stereo (which wouldn't go anywhere until Blumlein's
contributions). It was the Germans who first produced a standard artificial listener for evaluating
auditorium acoustics, and then played back the results over headphones -- the startling realism launched
binaural recording. A binaural recording is made using two microphones placed in the ear canals of an
anatomically accurate dummy head, such that all the normal spatial attributes of the human head are
present (just as in real listening situations) when the recording is made. Designed to be played back
through headphones, the results are nothing but astonishing. First time listeners to binaural recordings
often swear someone is there with them, talking and walking around them, such is the realism
accomplished. (7 of 14) [10/3/04 12:28:59 AM]
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binding post See: connectors.
binky See Larry Blake's Film Sound Glossary
bit Abbr. b Abbreviation for binary unit or binary digit. 1. The smallest amount of digital information. A
bit can store or represent only two states, 0 and 1. [The original term binary unit was coined by John
Tukey of Bell Laboratories to represent the basic unit of information as defined by Shannon as a message
representing one of two states.] 2. A little bit -- from Old English bita, meaning a piece bitten off.
bit clock The synchronizing signal that indicates the rate of individual data bits over a digital audio
bit error rate or bit error ratio See BER
bit rate The rate or frequency at which bits appear in a bit stream. Applied to digital audio, bit rate
(kbits/sec/channel) equals the sampling rate (kHz) times the number of bits per sample. The data bit rate
for a CD, for example, is 1.41M bits per second (44.1 kHz x 16 bits per sample x 2 channels). [The oftquoted CD bit rate of 4.3218 MHz is for the raw bit rate which comes from multiplying 7,350 frames per
second by 588, the number of channel bits.]
bits -- data converter See data converter bits
bit stream A binary signal without regard to grouping.
bit-mapped display A display in which each pixel's color and intensity data are stored in a separate
memory location.
Black, Harold S. (1898-1983) American electrical engineer and innovator most noted for his invention of
negative feedback (U.S. patent 2,102,671).
black hole music Name given by astronomers to detecting the deepest note ever generated in the cosmos,
a B-flat 57 octaves below middle C.
Blackmer, David (1927-2002). American scientist, inventor and businessman best known for founding
dbx, Inc. and pioneering audio-grade VCAs for signal processing.
black noise See noise color
black stick Clarinet. (Decharne) (8 of 14) [10/3/04 12:28:59 AM]
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blame shifter Shifts the pitch of mistakes down one octave so the audience thinks it was the bass player.
[Thanks to DD at Sound Path Labs.]
blue moon For half a century, it's been known as the second full moon in the same calendar month;
however, recently this definition was corrected by the editors of Sky & Telescope magazine. The correct
definition, they say, is that a blue moon occurs when a season has four full moons, rather than the usual
three. Further, they claim the misunderstanding is their fault based on an article they published in 1946.
For all the wonderful details, see Once In A Blue Moon
blue noise See noise color
Blu-ray Disc A trademark of Sony for their optical disc video recording format developed for recording,
rewriting and playback of HDTV, and is predicted to find its way into audio recording use.
Bluetooth The code name given a wireless network protocol, after a 10th century Danish king, Harald
Bluetooth, who unified Denmark. The code name was adopted in April, 1998, when Intel and Microsoft
formed a consortium between themselves IBM, Toshiba, Nokia, Ericsson and Puma Technology. This
protocol promised to bring wireless Internet to the masses, making the Web as ubiquitous as radio and
TV. The Bluetooth SIG (special interest group), now numbering over 2000 companies, sees a world
where equipment from different manufacturers works seamlessly together using Bluetooth as a sort of
virtual cable. Check out the website to read the whole history of Harald Bluetooth and get all the details.
Heavily challenged by Wi-Fi, which appears to have already accomplished what Bluetooth is still
promising. Compare with ZigBee.
blue whales See SPL
Blumlein, Alan Dower (1903-1942) English engineer who in a short working life span of 15 years wrote
or cowrote 128 patents, developed stereophonic sound, designed new uses for microphones, designed a
lateral disc-cutting system making modern records possible, developed much of the 405-line high
definition television system broadcast in Britain until 1986, and improved radar systems such that they
still operated 40 years later. Indeed, a genius by any definition, yet his story had to wait until 1999 to be
told completely. Thanks to Robert Charles Alexander, former editor of AudioMedia magazine, a
definitive biography now exists. Not only that, but Alexander has created a web site dedicated to
Blumlein that eventually will have all 128 patents reproduced in their entirety, along with all of his
binaural recordings (another of his inventions), downloadable as MP3 files, including binaural film clips
(the world's first stereo films).
BNC (bayonet Neill-Concelman) A miniature bayonet locking connector for coaxial cable. It was
developed in the late '40s by a collaboration of Paul Neill and Carl Concelman based on a patent granted
to the late Dr. Octavio M. Salati. In 1942, while at Bell Labs, Paul Neill developed what became known (9 of 14) [10/3/04 12:28:59 AM]
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as the type N connector, named after him, which became a U.S. Navy standard. Carl Concelman, while at
Amphenol, developed a bayonet version of the N connector, which became known as the type C
connector, after him (the first true 50-ohm connector). Then, together, they developed a miniature
bayonet locking version of the C connector and it was named the type BNC connector, after both of them.
There is even an improved threaded version called the threaded Neill-Concelman or TNC connector.
[Thanks to all who wrote me to help clarify this correct meaning. My condolences to all, who with
passion, conviction, and great creativity, truly believe differently. It is a sad but true tale that BNC does
NOT stand for "baby N connector," or "bayonet connector," or "bayonet Naval connector," or "British
Naval Connector" (sorry Microsoft). For further verification search the web for info on Paul Neill and
Carl Concelman.]
Boner, C.P. (1900-1979) American physicist specializing in acoustics, considered the father of room
equalization (U.S. patent 3,457,370).
boogaloo Nickname given to Abie "Boogaloo" Ames (1921-2002) in the 1940s for his boogie-woogie
(see below) piano style.
boogie-woogie A style of blues piano playing characterized by an up-tempo rhythm, a repeated melodic
pattern in the bass, and a series of improvised variations in the treble. (AHD)
Boole, George (1815-1864) British mathematician who devised a new form of algebra that represented
logical expressions in a mathematical form now known as Boolean Algebra. [See Maxfield]
boost/cut equalizer The most common graphic equalizer. Available with 10 to 31 bands, on 1-octave to
1/3-octave spacing. The flat (0 dB) position locates all sliders at the center of the front panel. Comprised
of bandpass filters, all controls start at their center 0 dB position and boost (amplify or make larger)
signals by raising the sliders, or cut (attenuate or make smaller) the signal by lowering the sliders on a
band-by-band basis. Commonly provide a center-detent feature identifying the 0 dB position. Proponents
of boosting in permanent sound systems argue that cut-only use requires adding make-up gain that runs
the same risk of reducing system headroom as boosting.
bop 1. A post-World War II style of jazz characterized by rhythmic and harmonic complexity, improvised
solo performances, and a brilliant style of execution. (AHD) The word "bebop" was shortened to "bob"
with Charlie Parker's 1947 recording "Bongo Bop." (Decharne) 2. "Playing bop is like playing Scrabble
with all the vowels missing." Duke Ellington, Look August 10, 1954. (Crystal)
Boucherot, Paul (1869-1943) French engineer who studied the phenomena of electric conduction,
introducing the concept of reactive power and inventing the synchronous electric motor in 1898. He also
studied the thermal energy of the seas. The Claude-Boucherot Process described a scheme to power a
turbo-alternator using warm seawater from tropical oceans to produce steam in a vacuum chamber.
Theorem of Boucherot: In an AC electrical network, the total active power is the sum of the individual (10 of 14) [10/3/04 12:28:59 AM]
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active powers, the total reactive power is the sum of the individual reactive powers, but the total apparent
power is NOT equal to the sum of the individual apparent powers.
Boucherot cell After Paul Boucherot above; see Zobel network
boundary microphone See PZM
Bozak, Rudy See: Bozak
BPL (broadband over power lines) General term for any of the "carrier-current" systems that conduct
signals over existing electrical wiring or power lines.
BPM (beats per minute) Music. A measure of music tempo. Used by disc jockeys to match beats to
produce a seamless segue, or transition, between songs.
Bps (always uppercase B) Abbreviation for bytes per second.
bps (always lowercase b) Abbreviation for bits per second.
Braille, Louis (1809-1852) French musician, educator, and inventor of a writing and printing system for
blind or visually impaired people (1829). He lost his sight at the age of three. [AHD] His braille system
was first developed for blind musicians.
brewer See zymurgy
brick wall filter Electronic Filters. A low-pass, high-pass or bandpass filter exhibiting extremely steep
rolloff rates of greater than 50 dB/octave such that the response resembles a "brick wall."
bridge 1. In communications networks a bridge is a device that connects two or more different networks
and forwards packets between them; specifically a device that (a) links or routes signals from one ring or
bus to another, or from one network to another, (b) may extend the distance and capacity of a single LAN
system, (c) performs no modification to packets or messages, (d) operates at the data-link layer of the OSI-Reference Model (Layer 2), (e) reads packets, and (f) passes only those with addresses on the same
segment of the network as the originating user. 2. A functional unit that interconnects two local area
networks that use the same logical link control (LLC) procedure, but may use different medium access
control (MAC) procedures. 3. A balanced electrical network, e.g., a Wheatstone bridge. Contrast with
briole Theater. Name for the adjustable wire ropes used for theater rigging, e.g., loudspeakers, lighting,
scenery, etc. (11 of 14) [10/3/04 12:28:59 AM]
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broadband Also wideband, a transmission medium having a bandwidth greater than a traditional
telephone (speech) channel (4 kHz). [Some argue that to be "broadband" the medium must support 20
kHz.] The most common broadband medium is coaxial cable carrying multiple audio, video and data
channels simultaneously. Each channel takes up a different frequency on the cable. There will be
guardbands, or empty spaces, between the channels to make sure each channel does not interfere with its
neighbor. The most common example is the CATV cable. Contrast with baseband.
broadcasting Networks. A message sent out available for anyone to receive (just like radio broadcast),
i.e., sending the same message to multiple recipients, as opposed to multicasting. Broadcasting sends a
message to everyone on the network; multicasting sends a message to a specified few.
brown noise See noise color
B&S gauge (Brown & Sharpe) See AWG.
BSI (British Standards Institute) The National Standards organization responsible for coordinating
standards preparation for sound equipment in the UK.
B-taper See potentiometer
buds See: IEM.
buffer In data transmission, a temporary storage location for information being sent or received.
buffer amplifier The IEEE dictionary defines buffer amplifier as "An amplifier in which the reaction of
output-load-impedance variation on the input circuit is reduced to a minimum for isolation purposes."
This is a bit confusing, but one thing is clear, it says that at the most fundamental level a buffer amplifier
isolates (or buffers) the loading effects (impedance) of two stages. It separates them, making them
independent. In analog designs, buffer amplifiers are used for just this purpose. If the next circuit stage in
a design has impedance characteristics that are detrimental to the preceding stage then a buffer amplifier
minimizes this interaction. And its use is not confined to analog design, digital circuits use buffers to
minimize similar loading effects.
The term "amplifier" comes about from the fact that most buffer amplifiers also provide either voltage or
current gain. In this sense, a normal audio power amplifier can be called a buffer amplifier - it buffers
your preamp from your very low impedance loudspeakers. [Historical Note: Sometimes a buffer amplifier
provides speed as well as isolation. In the mid '70s, National Semiconductor offered in their specialty
hybrid circuits line, a product simply named "Fast Buffer," whose purpose was to provide impedance
isolation, but could do so at high megawiggle speeds (not a trivial task back then), and if that wasn't good
enough, they also offered a "Damn Fast Buffer," that could really get the job done (true story).] As can (12 of 14) [10/3/04 12:28:59 AM]
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seen, the term buffer amplifier is a bit vague: it provides isolation, that much is sure, however, it may also
offer voltage gain, current gain, or both. And it may even provide an unbalanced-to-balanced function, or
bug A surprisingly old word used most often to connote a problem with a program or computer. From the
1896 edition of Hawkin's New Catechism of Electricity (Theo. Audel & Co.) comes this definition: "The
term `bug' is used to a limited extent to designate any fault or trouble in the connections or working of
electric apparatus." For a detailed study check out bug. To get rid of see: Agans.
Bulwer-Lytton Fiction Contest A whimsical literary competition that challenges entrants to compose the
opening sentence to the worst of all possible novels. Created by Professor Scott Rice, English
Department, at San Jose State University in 1982, the contest is still sponsored by the college. The name
comes from Edward George Earle Bulwer-Lytton, who wrote the famous line "It was a dark and stormy
night ..." as the opening words in his novel Paul Clifford (1830). Check it out -- great fun.
When Wilkie Collins's detective novel The Woman in White appeared in 1860, it created a considerable
stir. A feature much remarked upon was the villain, Count Fosco. One lady reader, however, was not so
impressed and wrote to tell Collins, "You really do not know a villain. Your Count Fosco is a very poor
one." She then offered to supply Collins with a villain next time he wanted one. "Don't think that I am
drawing upon my imagination. The man is alive and constantly under my gaze. In fact, he is my husband."
The writer was Bulwer-Lytton's wife. [Bartlett's Book of Anecdotes]
bumbershoot 1. An umbrella. Derived from an alteration of umbrella + alteration of (para)chute. (AHD)
2. A Seattle arts festival held each Labor Day weekend, featuring over 2,500 artists including comedians,
dancers, painters, poets, sculptors, tightrope walkers, acrobats, filmmakers, bookbinders, DJs, thespians,
and musicians of every genre -- from classical to hip-hop.
burnt-in time code See: time code
burst error A large number of data bits lost on the medium because of excessive damage to or
obstruction on the medium.
burst noise See popcorn noise
bus One or more electrical conductors used for transmitting signals or power from one or more sources to
one or more destinations. Often used to distinguish between a single computer system (connected together
by a bus) and multi-computer systems connected together by a network.
buss To kiss. (AHD)
Butterworth filter A type of electronic filter characterized by having a maximally flat magnitude (13 of 14) [10/3/04 12:28:59 AM]
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response, i.e., no amplitude ripple in the passband. [Contrast with Chebyshev] This circuit is based upon
Butterworth functions (or Butterworth polynomials). [For the mathematically inclined, these polynomials
represent a specialized solution to a general MacLaurin series based upon a Taylor series expansion.
Named after Stephen Butterworth, a British engineer who first described this response in his paper "On
the Theory of Filter Amplifiers," Wireless Engineer, vol. 7, 1930, pp. 536-541. Eleven years later, V.D.
Landon coined the phrase maximally flat in his paper "Cascade Amplifiers with Maximal Flatness," RCA
Review, vol. 5, 1941, pp. 347-362.]
Butterworth crossover The category of loudspeaker crossover design (or alignment) based on
Butterworth filters (see above).
byte Abbr. B A group of eight bits (a word) operating together. Usually abbreviated in uppercase to
distinguish "byte" from "bit" which uses lowercase "b". See: Bps
| 0-9 | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | Top |
Copyright © Rane Corporation. All rights reserved. (14 of 14) [10/3/04 12:28:59 AM]
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Pro Audio Reference
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C The electronic symbol for a capacitor.
C50 (dB); C80 (dB) Intelligibility. Clarity ratings; a logarithmic measure of the early-to-late arrival sound
energy ratio; for music the constant is 80 ms (C80) and for speech it is 50 ms (C50). Compare with D50
CABA (Continental Automated Buildings Association) An industry association that promotes advanced
technologies for the automation of homes and buildings in North America.
cables Audio systems use many different types of cables (for all the details see Lampen):
coaxial cable A single copper conductor, surrounded with a heavy layer of insulation,
covered by a thick surrounding copper shield and jacket. A constant-impedance unbalanced
transmission line.
data cable See data cables and Category cables.
fiber optics The technology of using glass fibers to convey light and modulated
information. Short distances (typically less than 150 feet) use plastic fibers, while long
distances must use glass fibers.
mic cable (aka audio cable) A shielded twisted-pair, usually designed for low current, high
flexibility and low handling noise. The best insulating materials are somewhat inflexible, so
most mic cables use rubber, neoprene, PVC, or similar materials, with small gauge wire,
and therefore, true mic cables are not intended for long runs. Unfortunately the term "mic
cable" has become synonymous with general-purpose audio cable (as distinguished from
speaker cable) when it can be quite different. The very best audio cable may not be the best
mic cable and vice versa.
quad mic cable or star-quad mic cable [a term coined by Canare for the first quad mic
cable, but was not trademarked and is now a generic term]. A four-conductor cable
exhibiting very low noise and hum pickup (hum reduction can be 30 dB better than
standard mic cable). The four conductors are wound together in a spiral, and then opposite
conductors are joined together at the connectors forming a two-conductor balanced line
(also called double balanced) with superior performance.
speaker cable An unshielded insulated pair, normally not twisted, characterized by heavy
(or large) gauge conductors (hence, low-resistance), used to interconnect the output of a
power amplifier and the input of a loudspeaker. The coupling between amplifier and (1 of 19) [10/3/04 12:29:09 AM]
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loudspeaker may be direct or via transformer (see constant voltage). The star quad design
described above also makes excellent speaker cables for use in high noise environments.
twisted-pair Standard two-conductor copper cable, with insulation extruded over each
conductor and twisted together. Usually operated as a balanced line connection. May be
shielded or not, abbreviated UTP (unshielded twisted-pair), or STP (shielded twisted-pair).
Cannon plug See connectors.
cans See: headphones.
capacitance A force that resists the sudden buildup of electric voltage (as opposed to inductance which
resists the sudden buildup of electric current). [IEEE]
capacitive reactance See impedance
capacitor Circuit symbol: C. 1. A device with the primary purpose of introducing capacitance into an
electric circuit. 2. An element within a circuit consisting of two conductors, each with an extended surface
exposed to that of the other, but separated by a layer of insulating material called the dielectric. Note: The
dielectric is designed so the electric charge on one conductor is equal in value but opposite in polarity to
that of the other conductor. [IEEE]
capacitor microphone See condenser microphone
capacitor standard values See: values
cardioid A heart-shaped plane curve, the locus of a fixed point on a circle that rolls on the circumference
of another circle with the same radius. (AHD)
cardioid microphone A directional microphone with an on-axis response shaped like a cardiod. Different
degress of caridiod-ness exist, termed subcardioid and hypercardioid.
carillon A stationary set of chromatically tuned bells in a tower, usually played from a keyboard. (AHD)
Cartesian coordinate system 1. A two-dimensional coordinate system in which the coordinates of a
point in a plane are its distances from two perpendicular lines that intersect at an origin, the distance from
each line being measured along a straight line parallel to the other. (AHD) 2. A three-dimensional
coordinate system in which the coordinates of a point in space are its distances from each of three
perpendicular planes that intersect at an origin. After the Latin form of Descartes, the mathematician who
invented it. (2 of 19) [10/3/04 12:29:09 AM]
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Category wiring A wire grading system developed by the EIA / TIA ("TIA/EIA 568-B: Commercial
Building Telecommunications Cabling Standard") describing UTP cabling (and hardware) with
transmission characteristics. Some of the most popular follow:
CAT 3 (Category 3 cable) Unshielded twisted-pair (UTP) data grade cable (usually 24
AWG). CAT 3 cables are characterized to 16 MHz and support applications up to 10 Mbps.
Typically used for voice telephone and 10Base-T Ethernet systems.
CAT 5 (Category 5 cable) Unshielded twisted-pair (UTP) data grade cable (usually 24
AWG). CAT 5 cable runs are limited to 100 meters (328 feet) due to signal radiation and
attenuation considerations. Longer runs are vulnerable to electromechanical interference.
CAT 5 cables are characterized to 100 MHz and support applications up to 100 Mbps. Most
common application is 100Base-T Ethernet systems. [With the release of ANSI/TIA/EIA568-B, CAT 5 is no longer recognized and is officially replaced by CAT 5e (see next
CAT 5e (Category 5 enhanced) As above CAT 5 cable except there is a plastic rib running
through the center of the cable that separates the pairs, maintaining greater distance
between them to reduce crosstalk ((they are other non-rib ways to meet this requirement). It
also keeps them in position to maintain the proper geometry along the whole cable. It uses
better insulation, making attenuation and crosstalk performance better. IT DOES NOT
EXTEND THE BANDWIDTH as some believe. The rated bandwidth is the same 100
MHz. It may run faster but the official specification (ANSI/TIA/EIA-568-B) does not
require it, so caveat emptor.
CAT 6 (Category 6) Proposed 300 MHz cabling is under study.
cathode Abbr. ka 1. A negatively charged electrode. 2. In a vacuum tube the electron emitting electrode.
3. In a forward-biased semiconductor diode it is the negative terminal. Contrast with anode.
cathode follower See buffer amplifier
CATV (community antenna television or cable television) A broadband transmission medium, most
often using 75-ohm coaxial cable carrying many TV channels simultaneously.
Cauer filters See: elliptic filters.
CAV (constant angular velocity) A disc rotating at a constant number of revolutions per second. The LP
is a CAV system at 33 1/3 rpm. Another example is the CAV laser disc that plays two thirty minute sides. (3 of 19) [10/3/04 12:29:09 AM]
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CBGB (country bluegrass blues) Famous Manhattan underground music club and gallery opened in
CBID (content-based indentification) The method of establishing intellectual property through a system
that does not embed digital watermarks into the audio data but instead uses algorithms to analyze an audio
segment to determine its unique characteristics (e.g., loudness, pitch, brightness and harmonicity).
CB Scheme (Certification Bodies Scheme) The official name is "Scheme of the IECEE for Mutual
Recognition of Test Certificates for Electrical Equipment."
CCIF (Comité Consultatif International des Téléphonique, or International Telephone Consultative
Committee) The CCIF merged with the CCIT becoming the CCITT. In 1992, the CCITT, together with
the CCIR, morphed into the ITU
CCIR (Comité Consultatif International des Radio Communications, or International Radio
Consultative Committee) (International Radio Consultative Committee) Merged with the ITU and
became the ITU-R radiocommunications division.
CCIR ARM See: weighting filters
CCIR-468 See: weighting filters
CCIR 2 kHz See: weighting filters
CCIT (Comité Consultatif International des Télégraphique, or International Telegraph Consultative
Committee) Merged with the CCIF to become the CCITT.
CCITT (Comité Consultatif International des Téléphonique et Télégraphique, or International
Telegraph and Telephone Consultative Committee) Merged with the ITU and became the ITU-T
telecommunications division.
CD (compact disc) Trademark term for the Sony-Philips digital audio optical disc storage system. The
system stores 80 minutes (maximum) of digital audio and subcode information, or other non-audio data,
on a 12-centimeter diameter optical disc. The disc is made of plastic, with a top metallized layer, and is
read by reflected laser light. Variations (such as the 3" disc) are reserved for special applications.
CD horn EQ See: constant directivity horn
CD-I (compact disc interactive) System storing digital audio, video, text, and graphics information (4 of 19) [10/3/04 12:29:09 AM]
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interactively, with user control over content and presentation, on a 12-centimeter diameter optical disc.
CD+MIDI A System storing MIDI information in a disc's subcode area.
CD-PROM (compact disc programmable read-only memory) A write-once CD-ROM disc.
CD-R (compact disc-recordable) A compact disc that is recordable at least once.
CD-ROM (compact disc read-only memory) A method of storing digitally coded information, such as
computer information or database, on a 12-centimeter diameter optical disc.
CD-V (compact disc video) A system storing five minutes of analog video and digital audio plus twenty
minutes of digital audio only on a 12-centimeter diameter optical disc, and longer times on 20- or 30centimeter diameter optical discs.
CEDIA (Custom Electronic Design & Installation Association) A global trade association of companies
that specialize in planning and installing electronic systems for the home.
CEI (Commission Electrotechnique Internationale) See IEC
Celsius Abbr. C Of or relating to a temperature scale that registers the freezing point of water as 0 °C and
the boiling point as 100 °C, under normal atmospheric pressure. (AHD) [The term "Celsius" is preferred
to "centigrade" in technical contexts.] [After Anders Celsius]
Celsius, Anders (1701-1744) Swedish astronomer who devised the centigrade thermometer (1742).
CEMA (Consumer Electronics Manufacturers Association) The definitive source for information about
the consumer electronics industry.
CE-mark (Conformité Européenne) The letter-logo used in marking units certified for distribution
within the European Union (EU) that meet the directives mandated by the European Commission.
center frequency One of the parameters of a bandpass filter. The center frequency occurs at the
maximum or minimum amplitude response for Butterworth filters, the most common found in audio
centi- Prefix for one hundredth (10E-2), abbreviated c.
centigrade Temperature term generally not used in scientific contexts apart from meteorology. See:
Celsius (5 of 19) [10/3/04 12:29:09 AM]
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ceptrum The word "spectrum" with the first four letters reversed. Created in 1963 by Bogert, Healy and
Tukey in their paper "The Quefrency Analysis of Time Series for Echoes: Cepstrum,
Pseudoautocovariance, Cross-Cepstrum, and Saphe Cracking." They observed that the logarithm of the
power spectrum of a signal containing an echo has an additive periodic component due to the echo, and
thus the Fourier transform of the logarithm of the power spectrum should exhibit a peak at the echo delay.
They called this function the "cepstrum," interchanging letters in the word spectrum because "in general,
we find ourselves operating on the frequency side in ways customary on the time side and vice versa."
The cepstrum is obtained in two steps: A logarithmic power spectrum is calculated and declared to be the
new analysis window. On that an inverse FFT is performed. The result is a signal with a time axis.
cereal interface A bowl and a spoon. [Thanks PM.]
CERN (Conseil Européenne pour la Recherche Nucléaire) European Particle Physics Laboratory. See:
World Wide Web
chachka or tchotchke also tsatske A cheap showy trinket, sometimes used as swag or a spiff. (AHD)
channel separation See crosstalk
charge Symbol q 1. Electricity. a. To cause formation of a net electric charge on or in (a conductor, for
example). b. To energize (a storage battery) by passing current through it in the direction opposite to
discharge. 2. Physics. a. The intrinsic property of matter responsible for all electric phenomena, in
particular for the force of the electromagnetic interaction, occurring in two forms arbitrarily designated
negative and positive. b. A measure of this property. c. The net measure of this property possessed by a
body or contained in a bounded region of space. (AHD)
chassis ground 1. The common point on a conducting chassis surrounding the system electronic circuit
boards; usually separate from the signal ground but may be tied at one point. 2. The earth grounding
connection provided on the chassis for safety reasons. See RaneNote: Sound System Interconnection
Chebyshev filter A class of electronic filter characterized by having an equiripple magnitude response,
meaning the magnitude increases and decreases regularly from DC to the cutoff frequency. Chebyshev
filters are classified by the amount of ripple in the passband, for example a 1 dB Chebyshev low-pass
filter is one with a magnitude response ripple of 1 dB. Chebyshev filters are popular because they offer
steeper roll-off rates than Butterworth filters for the same order, but for audio applications the Chebyshev
is virtually never seen due to the superior magnitude and phase responses of the Butterworth class. [After
Pafnuty Lvovich Chebyshev.]
Chebyshev, Pafnuty Lvovich [also spelled Tschebyscheff and Tchebysheff] (1821-1894) Russian
mathematician best remembered for his work on the theory of prime numbers. (AHD) (6 of 19) [10/3/04 12:29:09 AM]
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checksum The sum of a group of data items used for error checking. If the checksum received equals the
one sent, all is well. Otherwise, the receiving equipment requests the data be sent again.
chiasmus The term for a reversal in the order of words in two otherwise parallel phrases. For example,
the advice from the great sci-fi writer Ray Bradbury to aspiring writers: "You have to know how to accept
rejection and reject acceptance," or the familiar adage: "Say what you mean and mean what you say."
Christie, Samuel Hunter See Wheatstone bridge.
chorusing Recording. An effect where the audio signal is given multiple delays so as to sound like
several instruments playing at once. The delay times are short, typically 20-45 milliseconds, and each
delayed signal may be pitch-shifted. The effect is similar to hearing a “chorus,” where everyone is singing
the same thing but at slightly different times and pitches. Chorusing is a slightly elaborated version of
doubling. A signal is delayed approximately 15-35 milliseconds and mixed with the undelayed signal.
The delay time is modulated by a low-frequency-oscillator to achieve a shimmering effect due to a
combination of beat-frequencies and the slight pitch-bending that occurs as the delay time is changed.
chromatic scale Music. A scale consisting of 12 semitones.
chrominance 1. Abbreviated C. The color portion of the video signal - includes hue and saturation
information but not brightness. 2. VJ Jargon. A video filter that rejects color portions of an image. Used
by VJs to eliminate or feature specific image colors. Popular technique for blending images. (See:
Chrysler Air Raid Siren Promoted as "The Most Powrful Siren Ever Built," now a much sought after
collector's item. Powered by a 180 HP V-8 Chrysler Hemi® gasoline engine driving a three-stage
compressor blowing 2,610 cubic feet of air a minute into a giant siren rotor, with exit velocity of 400
miles per hour, the siren produced loudness levels of 138 dB SPL at a distance of 100 feet. Hit the link to
hear a sample. [Impressive.Thanks Rob!]
circuit-bendingThe popular art of altering low-cost electronic devices -- toys mostly -- to make them
produce new and unique sounds such as squawks, beeps and bongs, thus creating a homemade musical
instrument. Reed Ghazala is credited with inventing this new music genre.
circumaural Headphones. Literally "around the ear," thus headphones with earpieces surrounding the ear
and pressing against the side of the head, forming a seal to reduce ambient noise leakage. Compare with:
CISAC (Confederation Internationale des Societes d'Auterus et Compositeurs or The International
Confederation of Societies of Authors and Composers) An organization that works towards increased (7 of 19) [10/3/04 12:29:09 AM]
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recognition and protection of creator's rights.
CISC (complex instruction set computing) See: RISC
CISPR (Comite International Special des Perturbations Radioelectriques or International Special
Committee on Radio Interferance) Established in 1934 by a group of international organizations to
address radio interference.
clairaudience The supposed power to hear things outside the range of normal perception. [AHD] Also
called aural hallucination.
clarity index or clarity measure See: C50 (dB)
clamor Loud, usually sustained noise, as a public outcry of dissatisfaction. [AHD]
class-A An amplifier class
Class I equipment Equipment where protection against electric shock does not rely on basic insulation
only, but also provides an additional safety precaution allowing connection of the equipment to the
protective earth conductor in the fixed wiring of the installation so that accessible metal parts cannot
become live in the event of a failure of the basic insulation.
Class II equipment Equipment where protection against electric shock does not rely on basic insulation
only, but also provides additional safety precautions such as double insulation or reinforced insulation,
but there is no provision for connection of the equipment to the protective earth conductor.
clef Music. French, key, a symbol indicating the pitch represented by one line of a staff, in relation to
which the other pitches of the staff can be determined. [AHD]
client Any device connected to a server on a local area network (LAN), e.g., personal computer, DSPbased unit, workstation, etc.
clipping Term used to describe the result of an amplifier running into power supply limitation. The
maximum output voltage that any amplifier can produce is limited by its power supply. Attempting to
output a voltage (or current) level that exceeds the power supply results in a flattoping effect on the
signal, making it look cut off or "clipped." A clipped waveform exhibits extreme harmonic distortion,
dominated by large amplitude odd-ordered harmonics making it sound harsh or dissonant. Hard clipping
is the term used to describe extreme clipping of a signal, producing highly visible flattoped waveforms as
viewed on an oscilloscope; soft clipping refers to moderate clipping that results in waveforms having
softly-rounded edges, as opposed to the sharp edges of hard clipping. For how-to-avoid see RaneNote: (8 of 19) [10/3/04 12:29:09 AM]
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Setting Sound System Level Controls
clock A timing device that generates the basic periodic signal used as a source of synchronizing signals in
digital equipment.
CLV (constant linear velocity) A disc rotating at varying numbers of revolutions per second to maintain
a constant relative velocity between pickup and track across the disc radius. The CD is a CLV system
rotating from 500 rpm (lead-in track) to 200 rpm (lead-out track). Another example is the CLV laser disc
that plays two sixty minute sides.
CMR or CMRR See common-mode rejection (ratio)
coaxial Having or mounted on a common axis. [AHD]
coaxial cable A single copper conductor, surrounded with a heavy layer of insulation, covered by a thick
surrounding copper shield and jacket. A constant-impedance unbalanced transmission line. See cables.
coaxial loudspeaker Two or more transducers sharing a common axis. A common example is the car
speaker with a small tweeter mounted on axis and in front of the woofer cone. See Frazier white paper for
in-depth details.
CobraNetTM A trademark of Peak Audio (a division of Cirrus Logic) identifying their licensed
networking technology used for the deterministic and isochronous transmission of digital audio, video,
and control signals over 10 Mbit and 100 Mbit Ethernet networks.
codec (code-decode also compression-decompression) Originally a device for converting voice signals
from analog to digital for use in digital transmission schemes, normally telephone based, and then
converting them back again. Broaden now to mean an electronic device that converts analog signals, such
as video and voice signals, into digital form and compresses them to conserve bandwidth. Most codecs
employ proprietary coding algorithms for data compression, common examples being Dolby's AC-2,
ADPCM, and MPEG schemes. It is data compression (and direct digital video & audio inputs) that has
evolved the newer meaning of compression-decompression.
coincident-microphone technique See X/Y microphone technique
combining response See: interpolating response and RaneNote: Exposing Equalizer Mythology
common logarithm A logarithm based on the powers of 10 (aka base 10).
common-mode rejection (ratio) Abbr. CMR and CMRR The characteristic of a differential amplifier to (9 of 19) [10/3/04 12:29:09 AM]
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cancel all common-mode signals applied to its inputs. The "ratio" is obtained by dividing the input
common-mode voltage by the amount of output voltage, thereby giving you some measure of the
amplifier's ability to reject common signals. See RaneNote: Audio Specifications.
common-mode signal Strictly speaking it is the average of the signals present at the two inputs of a
differential amplifier, although it is more often meant to be the voltage level present at both inputs, as if
they were tied together.
compander A contraction of compressor-expander. A term referring to dynamic range reduction and
expansion performed by first a compressor acting as an encoder, and second by an expander acting as the
decoder. Normally used for noise reduction or headroom reasons.
complex frequency variable An AC frequency in complex number form. See complex number.
complex number Mathematics. Any number of the form a + bj, where a and b are real numbers and j is
an imaginary number whose square equals -1 (AHD); and a represents the real part (e.g., the resistive
effect of a filter, at zero phase angle) and b represents the imaginary part (e.g., the reactive effect, at 90
degrees phase angle).
component video A video system for color television that stores separate channels of red, green and blue.
Becoming increasingly popular on DVD players, as well.
composite video A video signal combining luminance, chrominance and synchronization data on a single
coax cable using RCA connectors and color-coded yellow.
compression 1. An increase in density and pressure in a medium, such as air, caused by the passage of a
sound wave. 2. The region in which this occurs.
compression wave A wave propagated by means of the compression of a fluid, such as a sound wave in
air. (AHD)
compressor A signal processing device used to reduce the dynamic range of the signal passing through it.
For instance, an input dynamic range of 110 dB might pass through a compressor and exit with a new
dynamic range of 70 dB. This clever bit of skullduggery is normally done through the use of a VCA
(voltage controlled amplifier), whose gain is a function of a control voltage applied to it. Thus, the control
voltage is made a function of the input signal's dynamic content. [Long answer: What "compression" is
and does has evolved significantly over the years. Originally compressors were used to reduce the
dynamic range of the entire signal; with modern advances in audio technology, compressors now are used
more sparingly. First the classical case: The history of compressors dates back to the late '20s and '30s
(the earliest reference I have located is a 1934 paper in the Bell Labs Journal.) The need arose the very
first time anyone tried to record (sound-motion pictures film recording, phonograph recording, etc.) or (10 of 19) [10/3/04 12:29:09 AM]
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broadcast audio: the signal exceeded the medium. For example, the sound from a live orchestra easily
equals 100 dB dynamic range. Yet early recording and broadcasting medium all suffered from limited
dynamic range. Typical examples: LP record 65 dB, cassette tape 60 dB (w/noise reduction), analog tape
recorder 70 dB, FM broadcast 60 dB, AM broadcast 50 dB. Thus "6 pounds of audio into a 4 pound bag"
became the necessity that mothered the invention of the compressor (sorry). Early compressors did not
have a "threshold" knob, instead, the user set a center ("hinge") point equivalent to the midpoint of the
expected dynamic range of the incoming signal. Then a ratio was set which determined the amount of
dynamic range reduction. The earlier example of reducing 110 dB to 70 dB requires a ratio setting of
1.6:1 (110/70 = 1.6). The key to understanding compressors is to always think in terms of increasing and
decreasing level changes in dB about some set-point. A compressor makes audio increases and decreases
smaller. From our example, for every input increase of 1.6 dB above the hinge point, the output only
increases 1 dB, and for every input decrease of 1.6 dB below the hinge point, the output only decreases 1
dB. If the input increases by x-dB, the output increases by y-dB, and if the input decreases by x-dB, the
output decreases by y-dB, where x/y equals the ratio setting. Simple - but not intuitive and not obvious.
This concept of increasing above the set-point and decreasing below the set-point is where this oft-heard
phrase comes from: "compressors make the loud sounds quieter and the quiet sounds louder." If the
sound gets louder by 1.6 dB and the output only increases by 1 dB, then the loud sound has been made
quieter; and if the sound gets quieter by 1.6 dB and the output only decreases by 1 dB, then the quiet
sound has been made louder (it didn't decrease as much). Think about it - it's an important concept. With
advances in all aspects of recording, reproduction and broadcasting of audio, the usage of compressors
changed from reducing the entire program to just reducing selective portions of the program. Thus was
born the threshold control. Now sound engineers set a threshold point such that all audio below this point
is unaffected, and all audio above this point is compressed by the amount determined by the ratio control.
Therefore the modern usage for compressors is to turn down (or reduce the dynamic range of) just the
loudest signals. Other applications have evolved where compressors are used in controlling the creation
of sound. For example when used in conjunction with microphones and musical instrument pick-ups,
compressors help determine the final timbre by selectively compressing specific frequencies and
waveforms. Common examples are "fattening" drum sounds, increasing guitar sustain, vocal
"smoothing," and "bringing up" specific sounds out of the mix, etc.] See RaneNote: Squeeze Me, Stretch
Me: The DC 24 Users Guide , RaneNote: Signal Processing Fundamentals, and RaneNote: Good
Dynamics Processing
condenser microphone [Also called capacitor microphone but more properly, the correct name is
electrostatic microphone.] A microphone design where a condenser (the original name for capacitor) is
created by stretching a thin diaphragm in front of a metal disc (the backplate). By positioning the two
surfaces very close together an electrical capacitor is created whose capacitance varies as a function of
sound pressure. Any change in sound pressure causes the diaphragm to move, which changes the distance
between the two surfaces. If the capacitor is first given an electrical charge (polarized) then this
movement changes the capacitance, and if the charge is fixed, then the backplate voltage varies
proportionally to the sound pressure. In order to create the fixed charge, condenser microphones require
external voltage (polarizing voltage) to operate. This is normally supplied in the form of phantom power
from the microphone preamp or the mixing console. (11 of 19) [10/3/04 12:29:09 AM]
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cone of confusion Hearing. If a sound presented to one ear is within an on-axis cone, then it is not
possible to locate it, due to the head blocking the sound from reaching the other ear (or attenuates it so
much that the brain ignores it). (The listener can tell from which side the sound comes from but cannot
locate it within the cone.) There is a similar effect for sounds occuring exactly in front, or to the rear,
where the sound does reach each ear but with the identical level and direction causing localization
confusion. If the sound is not heard differently by each ear, we cannot accurately localize the source. This
is called the "cone of confusion."
conjobble An English word no longer in print (except here) meaning to settle, arrange; to chat (late 17th
connectionless Networks. Protocols where the host sends messages without establishing connection with
the recipients. This is the "hope and pray" school: put the message on the network (with an address) and
"hope and pray" it arrives. Examples: Ethernet, and UDP are connectionless.
connection-oriented Networks. Protocols where the host sends messages directly to a connected receiver
(as opposed to connectionless above), i.e., the protocol requires a confirmed channel before transmission.
TCP/IP is connection-oriented.
connectors Audio equipment uses many types of connectors as follow (Also see: Connectors & Clark
[check "Technical Information" at bottom of page] for useful pin-out guides):
banana jack or banana plug A single conductor electrical connector with a banana-shaped springmetal tip most often used on audio power amplifiers for the loudspeaker wiring. Usually
configured as a color-coded molded pair (red = hot & black = return) on 3/4" spacing. Also used
for test leads and as terminals for plug-in components. The British still refer to these as a GR plug,
after General Radio Corporation, the inventor (according to The Audio Dictionary by Glenn D.
binding posts Alternate name for banana jacks above, derived from the capability to loosen
(unscrew) the body and insert a wire through a hole provided in the electrical terminal and tighten
the plastic housing down over the wire insulation, holding the wire in place.
BNC A miniature bayonet locking connector for coaxial cable. Used to interconnect S/PDIF
digital audio. See BNC for development and name history.
Cannon connector or Cannon plug Alternate reference for XLR.
Elco connector or Elco plug AVX manufactures several connectors used for interconnecting
multiple audio channels at once, most often found in recording studios on analog and digital audio
tape machines. One of these, a 90-pin version (Vari*con Series 8016), carries 28 shielded pairs of
audio channels, allowing 3-wires per channel (positive, negative & shield) for a true balanced
system interconnect.
Euroblocks Shortened form of European style terminal blocks, a specialized disconnectable, or
pluggable terminal block consisting of two pieces. The receptacle is permanently mounted on the
equipment and the plug is used to terminate both balanced and unbalanced audio connections using (12 of 19) [10/3/04 12:29:09 AM]
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screw terminals. Differs from regular terminal strips in its plugability, allowing removal of the
equipment by disconnecting the plug section rather than having to unscrew each wire terminal.
RCA (aka phono jack or pin jack) The Radio Corporation of America (RCA) originally developed
this type of unbalanced pin connector for internal chassis connections in radios and televisions
during the '30s. It became popular for use in the cables that connected phonograph cartridges to
preamplifiers because it was inexpensive and easily fitted to the rather small diameter shielded
cables used for the cartridge leads (then they were mono cartridges so single conductor shielded
cables were adequate -- now you know.). The standard connector used in line-level consumer and
project studio sound equipment, and most recently to interconnect composite video signals.
(excerpted from Yamaha Sound Reinforcement Handbook, pp. 297-298).
Speakon® A registered trademark of Neutrik for their original design loudspeaker connector, now
considered an industry de facto standard.
terminal strips or terminal blocks Also called barrier strips, a type of wiring connector provided
with screwdown posts separated by insulating barrier strips. Used for balanced and unbalanced
wiring connections, where each wire is usually terminated with a crimped-on spade- or ringconnector and screwed in place; not disconnectable, or pluggable. Has become known as the U.S.
style terminal blocks. Contrast with Euroblocks.
1/4" TRS (tip-ring-sleeve) 1. Stereo 1/4" connector consisting of tip (T), ring (R), and sleeve (S)
sections, with T = left, R = right, and S = ground/shield. 2. Balanced interconnect with the positive
& negative signal lines tied to T and R respectively and S acting as an overall shield. 3. Insert loop
interconnect with T = send, R = return, and S = ground/shield. [Think: ring, right, return]
1/4" TS (tip-sleeve) Mono 1/4" connector consisting of tip (T) [signal] and sleeve (S) [ground &
shield] for unbalanced wiring.
XLR 1. Originally a registered trademark of ITT-Cannon. The original model number series for
Cannon's 3-pin circular connectors - invented by them - now an industry generic term. [Ray A.
Rayburn tells the whole story: "At one time Cannon made a large circular connector series that was
popular for microphones called the P series (now known as the EP series). Mics used the 3-pin P3
version. Some loudspeakers use the P4 or P8 versions of this connector to this day (Neutrik
Speakon NL4MPR 4-pole chassis mount and all Speakon 8-pole chassis mount connectors are
made to fit the same mounting holes as the Cannon EP series). In an attempt to make a smaller
connector for the microphone market, Cannon came out with the UA series. These were "D"
shaped instead of circular and were used on such mics as the Electro-Voice 666 and 654. There
was a desire for a smaller yet connector. Someone pointed out the small circular Cannon X series.
The problem with this was it had no latch. Cannon rearranged the pins and added a latch, and the
XL (X series with Latch) was born. This is the connector others have copied. Later Cannon
modified the female end only to put the contacts in a resilient rubber compound. They called this
new version the XLR series. No other company has copied this feature."] 2. The standard
connector for digital and analog balanced line interconnect between audio equipment.
constant directivity (CD) horn (also known as uniform coverage or constant coverage horns) A hornloaded high frequency driver that exhibits more or less constant distribution of high-frequency sound in
the horizontal direction. This is done by using one of several special dual shaped horn designs created to (13 of 19) [10/3/04 12:29:09 AM]
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solve the traditional problem of horn-loaded driver output varying with frequency. All CD horns exhibit a
high frequency roll-off of approximately 6 dB/octave beginning somewhere in the 2 kHz to 4 kHz area.
Fixed EQ boost networks that compensate for this are known as CD horn EQ circuits.
constant group delay See: group delay
constant-Q equalizer (also constant-bandwidth) Term applied to graphic and rotary equalizers describing
bandwidth behavior as a function of boost/cut levels. Since Q and bandwidth are inverse sides of the same
coin, the terms are interchangeable. The bandwidth remains constant for all boost/cut levels. For constantQ designs, the skirts vary directly proportional to boost/cut amounts. Small boost/cut levels produce
narrow skirts and large boost/cut levels produce wide skirts. See RaneNote: Constant-Q Graphic
Equalizers, RaneNote: Operator Adjustable Equalizers, and RaneNote: Signal Processing Fundamentals
Compare with proportional-Q and true response equalizers.
constant splay array See: line arrays
constant-voltage The common name given to the general practices begun in the 1920s and 1930s
(becoming a U.S. standard in 1949) governing the interface between power amplifiers and loudspeakers
used in distributed sound systems. Installations employing ceiling-mounted loudspeakers, such as offices,
factories and schools are examples of distributed sound systems. The standard was derived from the need
to minimize cost and to simplify the design of complex audio systems. One way to minimize cost is to
minimize the use of copper, and one way to do that is to devise a scheme that allows the use of smaller
gauge wire than normal 8 ohm loudspeakers require. Borrowing from the cross-country power
distribution practices of the electric companies, this was done by using a transformer to step-up the
amplifier's output voltage (with a corresponding decrease in output current); use this higher voltage to
drive the (now smaller gauge due to smaller current) long lines to the loudspeakers; and then use another
transformer to step-down the voltage at each loudspeaker. Clever. This scheme became known as the
constant-voltage distribution method. The term "constant-voltage" is quite misleading and causes much
confusion until understood. Point 1: In electronics, two terms exist to describe two very different power
sources: "constant-current" and "constant-voltage." Constant-current is a power source that supplies a
fixed amount of current regardless of the load, so the output voltage varies, but the current remains
constant. Constant-voltage is just the opposite. The voltage stays constant regardless of the load, so the
output current varies but not the voltage. Applied to distributed sound systems, the term is used to
describe the action of the system at full power only. This is the key point in understanding. At full power
the voltage on the system will not vary as a function of the number of loudspeakers driven, that is, you
may add or remove (subject to the maximum power limits) any number of loudspeakers and the voltage
will remain the same, i.e., constant. Point 2: The other thing that is "constant" is the amplifier's output
voltage at rated power -- and it is the same voltage for all power ratings. Several voltages are used, but
the most common in the U.S. is 70.7 volts rms. The standard specifies that all power amplifiers put out
70.7 volts at their rated power. So, whether it is a 100 watt, or 500 watt or 10 watt power amplifier, the
maximum output voltage of each must be the same (constant) value of 70.7 volts. This particular number
came about from the second way this standard reduced costs: Back in the late '40s, UL safety code
specified that all voltages above 100 volts peak created a "shock hazard," and subsequently must be (14 of 19) [10/3/04 12:29:09 AM]
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placed in conduit. Expensive. Bad. So, working backward from a maximum of 100 volts peak (conduit
not required), you get a maximum rms value of 70.7 volts (Vrms = 0.707 Vpeak). [Often "70.7 volts" is
shortened to just "70 volts." It's sloppy; it's wrong; but it's common -- accept it.] In Europe, the most
common level is 100 volts rms (although 50 V and 70.7 V are used too). This allows use of even smaller
wire. Some large U.S. installations used as high as 210 volts rms, with wire runs of over one mile!
Remember, the higher the voltage the lower the current, and consequently the smaller the cable and the
longer the line can be driven without significant line loss. [The reduction in current exceeds the increase
in impedance caused by the smaller wire because of the current-squared nature of power.] In some parts
of the U.S., safety regulations regarding conduit use became stricter, forcing distributed systems to adopt
a 25 volt rms standard. This still saves conduit, but adds a considerable increase in copper cost, so its use
is restricted to small installations. Modern constant-voltage amplifiers either integrate the step-up
transformer into the same chassis, or employ a high voltage design to directly drive the line without the
need for the transformer. Similarly, constant-voltage loudspeakers have the step-down transformers builtin. Both 70.7 volt amplifiers and loudspeakers need only be rated in watts. An amplifier is rated for so
many watts output at 70.7 volts, and a loudspeaker is rated for so many watts input (to give a certain
SPL). Designing a system becomes a relatively simple matter of selecting speakers requiring so many
watts to achieve the target SPL (quieter zones use lower wattage speakers, etc.), and then adding up the
total to obtain the amplifier(s) power. For example, say you need (10) 25 watt, (5) 50 watt and (15) 10
watt loudspeakers, then you need at least 650 watts of amplifier power (actually you need about 1.5 times
this due to real world losses, but that's another story). [See RaneNote: Constant-Voltage Audio
Distribution Systems for more details]
content-based identification See: CBID.
contour control DJ mixers. A control found on professional DJ performance mixers used to change the
shape or taper (contour) of the fader action. Thus at, say, 50 % of travel, a fader may allow 50 %, or 10
%, or 90% of the audio signal to pass depending on the taper of the control. The contour control
(switched, continuous or stepped variable) changes this amount.
control voltage In audio electronic circuits using voltage-controlled amplifiers, or other gain-controllable
devices, a DC voltage proportional to the audio input signal amplitude, sometimes frequency dependent,
used to set the instantaneous gain of a VCA or other device. It is normally developed in the side-chain of
the electronic circuit.
convolution A mathematical operation producing a function from a certain kind of summation or integral
of two other functions. In the time domain, one function may be the input signal, and the other the
impulse response. The convolution than yields the result of applying that input to a system with the given
impulse response. In DSP, the convolution of a signal with FIR filter coefficients results in the filtering of
that signal.
Cook, Emory (1913-2002) American engineer and audio pioneer best known for his many contributions
to vinyl disc technology including the left-right binaural disc. He produced the first audiophile record in (15 of 19) [10/3/04 12:29:09 AM]
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1949 and demonstrated it at the Audio Fair in New York, subsequently founding the company Sounds of
Our Times, the first high fidelity record company. He was a founding member of the AES. Said to be the
first to record the sound of rain so accurate that it sounded "wet."
cooker wire A British term for the large gauge solid wire (i.e., not stranded) used for electric cookers.
Popularly used in ABX testing to confound and expose the aural hallucinations of those obsessed by
exotic loudspeaker wire.
copyright The legal right granted to an author, composer, playwright, publisher, or distributor to
exclusive publication, production, sale, or distribution of a literary, musical, dramatic, or artistic work.
(AHD) For an enlightening editorial, see: Joe Bob's (aka John Bloom) "Wrong copyright laws".
Corba (common object request broker architecture) An ORB (object request broker) standard developed
by the OMG (object management group). Corba provides for standard object-oriented interfaces between
ORBs, as well as to external applications and application platforms (from Newton's Telecom Dictionary).
Not to be confused with CobraNet.
corner frequency Same as -3 dB point, or the 3 dB down point; see passband.
correlation A mathematical operation that indicates the degree to which two signals are alike.
CORREQTTM (Computer Optimized Room Resonant EQualization Technique) Acronym created by
inventor Ken DeLoria for Apogee Sound International in 1991.
coupling or mutual coupling Loudspeakers. General term describing the combining behaviour of two or
more drivers reproducing the same frequency. If two or more identical loudspeakers are mounted such
that their acoustic centers are less than half a wavelength apart, their acoustic outputs over the frequency
range defined by the half wavelength distance will combine (couple) and propagate forward as one
waveform, thus two smaller drivers behave as one big driver. For example, two 12" drivers mounted with
their rims nearly touching will couple up to around 500 Hz.
CRC (cyclic redundancy check) An integrity checking process for block data. A CRC character is
generated at the transmission end. Its value depends on the hexadecimal value of the number of ones in
the data block. The transmitting device calculates the value and appends it to the data block. The
receiving end makes a similar calculation and compares its results with the added character. If there is a
difference, the recipient requests retransmission.
crap (completely ridiculous audio performance) Favorite acronym used to describe the characteristics of
poor sound equipment. (Thanks C.D.!)
creepage distance Shortest path along the surface of insulating material between two conductive parts. (16 of 19) [10/3/04 12:29:09 AM]
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crest factor The term used to represent the ratio of the peak (crest) value to the rms value of a waveform
measured over a specified time interval. For example, a sine wave has a crest factor of 1.4 (or 3 dB), since
the peak value equals 1.414 times the rms value. Music has a wide crest factor range of 4-10 (or 12-20
dB). This means that music peaks occur 12-20 dB higher than the rms value, which is why headroom is so
important in audio design.
critical band Physiology of Hearing. A range of frequencies that is integrated (summed together) by the
neural system, equivalent to a bandpass filter (auditory filter) with approximately 10-20% bandwidth
(approximately one-third octave wide). [Although the latest research says critical bands are more like 1/6octave above 500 Hz, and about 100 Hz wide below 500 Hz.] The ear can be said to be a series of
overlapping critical bands, each responding to a narrow range of frequencies. Introduced by Fletcher
(1940) to deal with the masking of a pure-tone by wideband noise.
cross-coupled A type of balanced line driver loosely based on servo-loop technology. Developed to
emulate some of the features of a balanced line output transformer, the circuit employs positive feedback
taken from each side of the outputs coupled back (cross-coupled) to the opposite input circuitry where it
is used to fix the gain of the positive and negative line drivers. Each gain is typically set to unity (one) for
normal operation and changes to two whenever either of the output lines is shorted to zero. In this manner,
it emulates a transformer in that there is no change in output level if one of the lines becomes shortcircuited to ground; however, since the gain of the ungrounded side has increased 6 dB then the headroom
of the system has been reduced by 6 dB due to the short. In this sense this circuit does not act like a
transformer, which does not change gain when one side is shorted to ground. See RaneNote: Unity Gain
and Impedance Matching: Strange Bedfellows
crossfade or crossfader Within the pro audio industry, a term most often associated with DJ mixers and
broadcast. DJ mixers usually feature a crossfader slide-type potentiometer control. This control allows the
DJ to transition from one stereo program source (located at one travel extreme) to another stereo program
source (located at the other travel extreme). It is the crossfader that becomes the main remix tool for
turntablists. The exact origin of the first use of a crossfader in the DJ world has proven difficult to track
down. It seems certain to have come out of the broadcast industry, where the term "fader" has been in use
since at least the '50s (mentioned throughout the Radiotron Designer's Handbook, 4th ed., 1952) and the
term "cross-fading" shows up in the Tremaine's Audio Cyclopedia in 1973. Richard Wadman, one of the
founders of the British company Citronic designed the earliest example documented so far. It was called
the model SMP101, made about 1977, and had a crossfader that doubled as a L/R balance control or a
crossfade between two inputs. [Anyone who can document an earlier example of a DJ crossfader please
write me.]
For a history of DJ-use crossfader circuitry see Evolution of the DJ Mixer Crossfader by Rane's ace DJ
mixer designer, Rick Jeffs, for additional details. Contrast with pan, balance and fader controls.
cross-framing A term borrowed from the construction industry (meaning diagonal bracing) by TimeLine (17 of 19) [10/3/04 12:29:09 AM]
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Vista, Inc. (now defunct) the original developer and manufacturer of the TASCAM-branded MX-2424
(24-track, 24-bit hard disk recorder) to describe their sync product with "independent cross-framing"
capability that allows a longitudinal timecode (LTC) reader and two generators to be set to different frame
crossover An electrical circuit (passive or active) consisting of a combination of high-pass, low-pass and
bandpass filters used to divide the audio frequency spectrum (20 Hz - 20 kHz) into segments suitable for
individual loudspeaker use. Since audio wavelengths vary from over 50 feet at the low frequency end, to
less than one inch at the high frequency end, no single loudspeaker driver can reproduce the entire audio
range. Therefore, at least two drivers are required, and more often three or more are used for optimum
audio reproduction. Named from the fact that audio reproduction transitions (or crosses over) from one
driver to the next as the signal increases in frequency. For example, consider a two driver loudspeaker
crossed over at 800 Hz: Here only one driver (the woofer - "woof, woof" = low frequencies) works to
reproduce everything below 800 Hz, while both drivers work reproducing the region immediately around
800 Hz (the crossover region), and finally, only the last driver (the tweeter - "tweet, tweet" = high
frequencies) works to reproduce everything above 800 Hz. Crossover circuits are characterized by their
type (Butterworth, Bessel and Linkwitz-Riley being the most popular), and by the steepness of their rolloff slopes (the rate of attenuation outside their passbands) as measured in decibels per interval, such as
dB/octave, or sometimes dB/decade [useful rule-of-thumb: 6 dB/octave approximately equals 20
dB/decade]. See RaneNote: Signal Processing Fundamentals
crosspoint Audio Signal Processing. Found in matrix-mixers, referring to a device, usually a switch,
potentiometer, VCA or DAC, located where two schematic or block diagram lines intersect or cross.
Typically this is drawn with the inputs entering from the left and exiting to the top depending upon the
setting of the crosspoint device. For example if Input 4 is to exit Output 6 then at the intersection of Input
4's signal path and Output 6's exit path there will be a switch that is closed, or a potentiometer set for
something other than off, or a VCA or DAC that is at least partially turned up. Crosspoints form the heart
of a router.
crosstalk (recording) See: print-through
crosstalk (signal) 1. Undesired capacitive, inductive, or conductive coupling from one circuit, part of a
circuit, or channel, to another. 2. Any phenomenon by which a signal transmitted on one circuit or
channel of a transmission system creates an undesired effect in another circuit or channel. Note: In
telecommunications, crosstalk is usually distinguishable as speech or signaling tones. See RaneNote:
Audio Specifications
crystal See: piezo.
cue 1. A term found throughout various audio fields meaning to monitor, or listen (via headphones) to a
specific source. In mixers (particularly DJ mixers), the term is used interchangeably with solo or PFL as (18 of 19) [10/3/04 12:29:09 AM]
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found on recording consoles. 2. Music. a. A section of music used in film or video ranging from a short
piece of background music to a complex score. b. An extract from the music for another part printed,
usually in smaller notes, within a performer's part as a signal to enter after a long rest. c. A gesture by a
conductor signaling the entrance of a performer or part. 3. A signal, such as a word or an action, used to
prompt another event in a performance, such as an actor's speech or entrance, a change in lighting, or a
sound effect. (AHD)
current Symbol i, I Electricity. a. A flow of electric charge. b. The amount of electric charge flowing past
a specified circuit point per unit time, or the rate of flow of electrons. (AHD) [As electrons flow in one
direction, the spaces left behind, called holes, appear to flow in the opposite direction. Thus, current can
be visualized as electron flow (negative current flow), or in the opposite direction, hole flow (positive
current flow, sometimes called conventional current flow).]
current loop A data transmission scheme that looks for current flow rather than voltage levels. This
systems recognizes no current flow as a binary zero, and having current flow as a binary one. Favored for
its low sensitivity to cable impedance, and independence of a common ground reference; hence current
loops do not introduce ground loops. MIDI is an example of a current loop interconnect system.
cut-only equalizer Term used to describe graphic equalizers designed only for attenuation. (Also referred
to as notch equalizers, or band-reject equalizers). The flat (0 dB) position locates all sliders at the top of
the front panel. Comprised only of notch filters (normally spaced at 1/3-octave intervals), all controls start
at 0 dB and reduce the signal on a band-by-band basis. Proponents of cut-only philosophy argue that
boosting runs the risk of reducing system headroom.
cutoff frequency Filters. The frequency at which the signal falls off by 3 dB (the half power point) from
its maximum value. Also referred to as the -3 dB points, or the corner frequencies.
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D50 (%) Intelligibility. A linear measure of the early-to-total energy ratio expressed in percentage.
Compare with C50 (dB).
DA-88 Tascam's model number for their digital multitrack recorder using Sony-developed "Hi8" 8 mm
videotape as the storage medium. Becoming a generic term describing this family of recorders. See:
DA (distribution amplifier) Common abbreviation used throughout the broadcast, telecommunication
and sound consulting/contracting fields.
DAA (Digital Access Arrangement) Telephony. Name for the physical connection to the telephone line
known as the local loop. The DAA performs the four critical functions of line termination, isolation,
hybrid, and ring detection.
DAB (digital audio broadcast) 1. NRSC (National Radio Systems Committee) term for the next
generation of digital radio broadcast. 2. Initials of the compiler of this Pro Audio Reference.
DAC (or D/A, digital-to-analog converter) The electronic component which converts digital words into
analog signals that can then be amplified and used to drive loudspeakers, etc. The DAC is the last link in
the digital chain of signal processing. See data converter bits
damping factor Damping is a measure of a power amplifier's ability to control the back-emf motion of
the loudspeaker cone after the signal disappears. The damping factor of a system is the ratio of the
loudspeaker's nominal impedance to the total impedance driving it. Perhaps an example best illustrates
this principle: let's say you have a speaker cabinet nominally rated at 8-ohms, and you are driving it with
a Rane MA 6S power amp through 50 feet of 12 gauge cable. Checking the MA 6S data sheet (obtained
off this web site, of course), you don't find its output impedance, but you do find that its damping factor is
300. What this means is that the ratio of a nominal 8 ohm loudspeaker to the MA 6S's output impedance
is 300. Doing the math [8 divided by 300] comes up with an amazing .027 ohms. Pretty low. Looking up
12 gauge wire in your handy Belden Cable Catalog (... then get one.) tells you it has .001588 ohms per
foot, which sure ain't much, but then again you've got 100 feet of it (that's right: 50 feet out and 50 feet
back -- don't be tricked), so that's 0.159 ohms, which is six times as much impedance as your amplifier.
(Now there's a lesson in itself -- use big cable.) Adding these together gives a total driving impedance of (1 of 16) [10/3/04 12:29:17 AM]
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0.186 ohms -- still pretty low -- yielding a very good damping factor of 43 (anything over 10 is enough,
so you don't have to get extreme about wire size). [Note that the word is damp-ing, not damp-ning as is so
often heard -- correct your friends; make enemies.]
DAR (digital audio radio) EIA term for the next generation of digital radio broadcasting standards.
DASH (digital audio stationary head) A family of formats for ensuring compatibility among digital
multitrack studio recorders using stationary (as opposed to rotating) heads. The DASH standard,
popularized by Sony and Studer, specifies 2 to 48 tracks, with tape speeds from 12 to 76 cm/sec.
DAT (digital audio tape recorder ) 1. A digital audio recorder utilizing a magnetic tape cassette system
with rotary heads similar to that of a video recorder. 2. A little bit of something as in dis & dat.
data cables Analog audio signals require a relatively small bandwidth and are interconnected using
standard cables. In contrast to analog audio, digital audio and digital control signals require a very large
bandwidth and must be interconnected with specially designed data cables. See Category cables.
data compression See: digital audio data compression
data converter bits The number of bits determines the data converter precision. The more bits available,
the more precise the conversion, i.e., the closer the digital answer will be to the analog original. When an
analog signal is sampled (at the sampling frequency), it is being sliced up into vertical pieces. Each
vertical piece is then estimated as to its amplitude (How large is the audio signal at this instant?). This
estimation process is the data converters job. It compares the original signal against its best estimate and
chooses the closest answer. The more bits, the more choices the data converter has to choose from. The
number of choices is the number "2" raised to the number of bits (this explanation is simplified for
clarity). For example, 16-bits creates 2 to the 16th power of choices, or 65,536 possible answers for the
converter to choose from. And the higher the sampling rate, the more slices for any given time period.
Again, the more slices, the more accurate will be the data conversion. All of which, ultimately determines
how well the reproduced signal sounds compared to the original. For example, if a signal is recorded
using "16-bits at 48 kHz", then for every one second of the audio signal, it is sliced up into 48,000 pieces.
Then each piece is compared against a ruler with 2 to the 16th graduations, or 65,536 voltage levels. Each
sample instant is compared against this ruler and one value is assigned to represent its amplitude. For
each second, 48,000 samples are given specific values to represent the original signal. If the same signal
is recorded using "24-bits at 96 kHz" then for the same one second period, there will be 96,000 slices, or
samples, and each one will be compared against a voltage ruler now divided into 2 to the 24th divisions,
or 16,777,216 choices. Obviously this converter can choice an answer that is far closer to the original
than before, and it gets to do this for twice as many samples. All of which, in the end, means this
converter recorded samples that more closely approximated the original audio signal. [Where it gets
interesting is in trying to answer the question of what is enough? Sure, more bits are more accurate, but
can the human ear tell the difference. In most cases, once you go beyond true 16-bits, the answer is no. (2 of 16) [10/3/04 12:29:17 AM]
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All benefits above 16-bits/48 kHz are very small refinements, not monumental improvements. What really
is going on, is that the advertised "16-bit/48 kHz" recordings of yesterday weren't. They used 16-bit
converters but their accuracy was not 16-bits, it was more like 14-bits. Similarly today, the advertised
"24-bit" converters are not 24-bit accurate, but they are certainly at least 18-bit accurate, and that makes
an audible difference. So, if you can find a true 16-bit system and compare it with a typical 24-bit system
of today, they will sound very nearly identical. And the sampling rate getting faster makes even less of an
audible difference. For example if you compare a typical 16-bit/96 kHz system against a 24-bit/48 kHz,
you will pick the 24-bit system every time. If you have a choice, always choose more bits, over a higher
sampling rate.] See RaneNote: Digital Dharma of Audio A/D Converters
DAW (digital audio workstation) Any of several software/hardware systems using a computer as the
basis for creating, editing, storing, and playback of digital audio, using the computer's hard disk as the
recording medium, or a SAN.
DB-9 connector (Note: the correct term is DE-9 but has lost out to this popular misusage. DE is the
shell size for a 9-pin connector; DB is the shell size for a 25-pin connector. See Ishmael StefanovWagner's D-Subminiature Nomenclature for details) A smaller 9-pin version of the connector used for
RS-232 communications. First made popular by IBM in their AT personal computer in the mid-80s. [The
“D” originally described the shape of the housing. The second letter: A, B, C D or E originally specified
the size of the housing somewhat like drawing sizes. (Newton)]
DB-25 connector A 25-pin D-shell connector originally standardized for RS-232 serial communications.
dB (decibel) See: decibel
dBA Unofficial but popular way of stating loudness measurements made using an A-weighting curve.
dBC Unofficial but popular way of stating loudness measurements made using an C-weighting curve.
dB drag racer Term applied to auto sound enthusiasts that travel the world to compete in loudness
contests. Current record is over 177 dB-SPL (yes, 177 dB-SPL!).
DCA (digitally-controlled attenuator) Also digitally-controlled analog and digitally-controlled
DCC (Digital Compact Cassette) Philips's digital version of the standard analog cassette tape system. A
DCC recorder plays and records digital cassettes, as well as playing analog cassettes. [Now
DCE (Data Communications Equipment) Within the RS-232 standard, the equipment that provides the
functions required to establish, maintain, and terminate a connection, as well as the signal conversion, (3 of 16) [10/3/04 12:29:17 AM]
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and coding required for communication between data terminal equipment and data circuit - e.g., a modem
or printer. See: DTE. The main difference between DCE and DTE is the wiring of pins 2 and 3, thus the
need for a null modem cable when tying two computers together.
DE-9 connector See: DB-9 connector
deadly nevergreen An English word no longer in print (except here) meaning the gallows (late 18th,
early 19th centuries).
Dead Musician Directory "A site about dead musicians ... and how they got that way" Hey! Don't laugh,
these guys are dead serious. Dead Rockers, jazz, reggae, bluegrass, etc.
Dead Recording Media (This was the original name, now renamed The History of Sound Recording
Technology. I guess someone complained.) A great chronicle of obsolete devices compiled by David L.
Morton: "... site devoted to the dead, dying, or very ill technologies of sound recording."
decay Electronics. A gradual magnitude decrease of signal level, ocurring immediately after a signal
reaches its peak. Contrast with attack.
decibel Abbr. dB Equal to one-tenth of a bel. [After Alexander Graham Bell.] 1. A measuring system
first used in telephony (Martin, W.H., "DeciBel -- the new name for the transmission unit. Bell System
Tech. J. January, 1929), where signal loss is a logarithmic function of the cable length. 2. The preferred
method and term for representing the ratio of different audio levels. It is a mathematical shorthand that
uses logarithms (a shortcut using the powers of 10 to represent the actual number) to reduce the size of
the number. For example, instead of saying the dynamic range is 32,000 to 1, we say it is 90 dB [the
answer in dB equals 20 log x/y, where x and y are the different signal levels]. Being a ratio, decibels have
no units. Everything is relative. Since it is relative, then it must be relative to some 0 dB reference point.
To distinguish between reference points a suffix letter is added as follows [The officially correct way per
AES-R2, IEC 60027-3 & IEC 60268-2 documents is to enclose the reference value in parenthesis
separated by a space from "dB"; however this never caught on, probably for brevity reasons if no other.]:
0 dBu Preferred informal abbreviation for the official dB (0.775 V); a voltage reference
point equal to 0.775 Vrms. [This reference originally was labeled dBv (lower-case) but was
too often confused with dBV (upper-case), so it was changed to dBu (for unterminated).]
+4 dBu Standard pro audio voltage reference level equal to 1.23 Vrms.
0 dBV Preferred informal abbreviation for the official dB (1.0 V); a voltage reference point
equal to 1.0 Vrms.
-10 dBV Standard voltage reference level for consumer and some pro audio use (e.g. (4 of 16) [10/3/04 12:29:17 AM]
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TASCAM), equal to 0.316 Vrms. (Tip: RCA connectors are a good indicator of units
operating at -10 dBV levels.)
0 dBm Preferred informal abbreviation of the official dB (mW); a power reference point
equal to 1 milliwatt. To convert into an equivalent voltage level, the impedance must be
specified. For example, 0 dBm into 600 ohms gives an equivalent voltage level of 0.775 V,
or 0 dBu (see above); however, 0 dBm into 50 ohms, for instance, yields an equivalent
voltage of 0.224 V -- something quite different. Since modern audio engineering is
concerned with voltage levels, as opposed to power levels of yore, the convention of using
a reference level of 0 dBm is obsolete. The reference levels of +4 dBu, or -10 dBV are the
preferred units.
0 dBr An arbitrary reference level (r = re; or reference) that must be specified. For
example, a signal-to-noise graph may be calibrated in dBr, where 0 dBr is specified to be
equal to 1.23 Vrms (+4 dBu); commonly stated as "dB re +4," that is, "0 dBr is defined to
be equal to +4 dBu."
0 dBFS A digital audio reference level equal to "Full Scale." Used in specifying A/D and
D/A audio data converters. Full scale refers to the maximum peak voltage level possible
before "digital clipping," or digital overload (see overs) of the data converter. The Full
Scale value is fixed by the internal data converter design, and varies from model to model.
[According to standards people, there's supposed to be a space between "dB" and "FS" -yeah, right, like that's gonna happen.]
0 dBf Preferred informal abbreviation of the official dB (fW); a power reference point
equal to 1 femtowatt, i.e., 10-15 watts.
0 dB-SPL The reference point for the threshold of hearing, equal to 20 microPA (micro
Pascals rms).
Since 1 PA = 1 newton/m2 = .000145 PSI (pounds per square inch)
Then 0 dB-SPL = 2.9 nano PSI (rms) -- an unbelievably small value.
This means that since 1 atm = 14.7 PSI, it is equivalent to a loudness level of 194 dB-SPL!
[Thanks to Bob Pease for pointing out these enlightening facts!]
dBA Unofficial but popular way of stating loudness measurements made using an Aweighting curve.
dBC Unofficial but popular way of stating loudness measurements made using an C (5 of 16) [10/3/04 12:29:17 AM]
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weighting curve.
decimal digit Everyday normal, base-10 numbers.
DED (pronounced "dead") (dark emitting diode) A variation of LED technology used exclusively by the
CIA for clandestine equipment. Also popular as power-off indicators.
de-emphasis See: pre-emphasis
de-esser A special type of audio signal compressor that operates only at high frequencies (>3 kHz), used
to reduce the effect of vocal sibilant sounds.
De Forest, Lee (1873-1961) Known as "the Father of Radio," he was an American electrical engineer
who patented the triode electron tube (1907) that made possible the amplification and detection of radio
waves. He originated radio news broadcasts in 1916. (AHD)
deja-booboo "The inexorable feeling that you've made this mistake before." --
delay 1. Crossovers. A signal processing device or circuit used to delay one or more of the output signals
by a controllable amount. This feature is used to correct for loudspeaker drivers that are mounted such
that their points of apparent sound origin (not necessarily their voice coils) are not physically aligned.
Good delay circuits are frequency independent, meaning the specified delay is equal for all audio
frequencies (constant group delay). Delay circuits based on digital sampling techniques are inherently
frequency independent and thus preferred. 2. MI. Digital audio delay circuits comprise the heart of most
all "effects'' boxes sold in the MI world. Reverb, flanging, chorusing, phasers, echoing, looping, etc., all
use delay in one form or another. 3. Sound Reinforcement. Acousticians and sound contractors use signal
delay units to "aim" loudspeaker arrays. Introducing small amounts of delay between identical, closelymounted drivers, fed from the same source, controls the direction of the combined response.
delay skew Category wiring. The time arrival difference between received signals at the far end. For
example, the maximum allowed in CAT 5e wiring is 45 ns.
delta modulation A single-bit coding technique in which a constant step size digitizes the input
waveform. Past knowledge of the information permits encoding only the differences between consecutive
delta-sigma ADC See: delta-sigma modulation
delta-sigma modulation (also sigma-delta) An analog-to-digital conversion scheme rooted in a design
originally proposed in 1946, but not made practical until 1974 by James C. Candy. Inose and Yasuda (6 of 16) [10/3/04 12:29:17 AM]
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coined the name delta-sigma modulation at the University of Tokyo in 1962, but due to a
misunderstanding the words were interchanged and taken to be sigma-delta. Both names are still used for
describing this modulator. Characterized by oversampling and digital filtering to achieve high
performance at low cost, a delta-sigma A/D thus consists of an analog modulator and a digital filter. The
fundamental principle behind the modulator is that of a single-bit A/D converter embedded in an analog
negative feedback loop with high open loop gain. The modulator loop oversamples and processes the
analog input at a rate much higher than the bandwidth of interest (see: Sampling (Nyquist) Theorem). The
modulator's output provides 1-bit information at a very high rate and in a format that a digital filter can
process to extract higher resolution (such as 20-bits) at a lower rate. See RaneNote: Digital Dharma of
Audio A/D Converters
dempo "In music, taking a song or a part of a song down tempo, or slower."
Compare with: umpo.
denominator Mathematics. The bottom part of a common fraction.
Descartes, René (1596-1650) French mathematician and philosopher. Considered the father of analytic
geometry, he formulated the Cartesian system of coordinates. [Then there's the story about how Descartes
met his ultimate demise: It seems he was in a bar in Paris sipping a glass of Kir when the bartender asked
if he would like another. M. Descartes responded "I think not," whereupon he disappeared without a
trace.] (Thanks to Glenn D. White for this.)
deserializer A serial-to-parallel data converter; used in buses and networks.
destructive solo See: solo
DI (digital audio input) AES3 (& IEC 60958-4) abbreviation to be used for panel marking where space
is limited and the function of the XLR AES3 connector might be confused with an analog signal
DI (direct) box See direct box
diatonic 1. Music. Of or using only the eight tones of a standard major or minor scale without chromatic
deviations. (AHD) 2. A popular summer drink without the gin or the sugar.
dichotic Hearing. Pertaining to different sounds present at both ears. Contrast: diotoc
dichotic listening Hearing. Listening to a different message in each ear at the same time. Try: A Dichotic
Listening Experiment (7 of 16) [10/3/04 12:29:17 AM]
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dictionary "A malevolent literary device for cramping the growth of a language and making it hard and
inelastic. This dictionary, however, is a most useful work." -- Ambrose Bierce.
difference-tone IMD See: IM
differential amplifier Electronics. A three-terminal analog device consisting of two inputs designated
positive and negative and one output that responds to the difference in potential between them.
diffraction Acoustics. The bending of waves around obstacles and the spreading of waves through
openings that are approximately the same as the wavelength of the waves. See link.
diffraction grating A usually glass or polished metal surface having a large number of very fine parallel
grooves or slits cut in the surface and used to produce optical spectra by diffraction of reflected or
transmitted light. (AHD)
diffuse Widely spread out or scattered; not concentrated. (AHD)
diffuser (or diffusor, British spelling; in acoustics, the British spelling is seen most often.) A commercial
device that diffuses, or scatters sound. First invented by Manfred R. Schroeder ["Diffuse Sound
Reflection by Maximum-Length Sequences," J. Acoust. Soc. Am., Vol. 57, No. 1, pp 149-150, Jan 1975],
and made commercially successful by Dr. Peter D'Antonio and his company RPG Diffusor Systems.
Diffusors are the acoustical analog of diffraction grating -- see above.
digital audio The use of sampling and quantization techniques to store or transmit audio information in
binary form. The use of numbers (typically binary) to represent audio signals.
digital audio data compression Commonly shortened to "audio compression." Any of several
algorithms designed to reduce the number of bits (hence, bandwidth and storage requirements) required
for accurate digital audio storage and transmission. Characterized by being "lossless" or "lossy." The
audio compression is "lossy" if actual data is lost due to the compression scheme, and "lossless" if it is
not. Well-designed algorithms ensure "lost" information is inaudible - that's how you win the game.
digital audio recording formats See The Digital Revolution compiled by Steve E. Schoenherr -outstanding compilation beginning in 1937 with the invention of PCM by Alec H. Reeves.
digital audio watermarking See watermarking
digital clipping See: 0 dBFS
digital filter Any filter accomplished in the digital domain. (8 of 16) [10/3/04 12:29:17 AM]
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digital hybrid See: hybrid
digital overs See: overs
digital signal Any signal which is quantized (i.e., limited to a distinct set of values) into digital words at
discrete points in time. The accuracy of a digital value is dependent on the number of bits used to
represent it.
digitization Any conversion of analog information into a digital form.
Dilettante's Dictionary Great audio/video/recording/computing dictionary started and maintained by
Sandy Lerner, one of the founders of Cisco Systems.
diminished fifth 1. A fifth is an interval of 3:2 (interval is the ratio of frequencies between a base note
and another note). A diminished fifth is a half step lower. 2. What's left after you've had a few shots.
[Thanks GD]
din A jumble of loud, usually discordant sounds. [AHD]
DIN Acronym for Deutsche Industrie Norm (Deutsches Institut fuer Normung), the German
standardization body.
diode Semiconductor. A two-terminal device consisting of a cathode and anode that conducts only in one
direction of polarity.
diotic Hearing. Pertaining to the identical sound present at both ears. Contrast: dichotic
dipless crossfader A crossfader design that does not attenuate the first audio signal until the fader is
moved past the 50% travel point, while simultaneously increasing the second audio signal to 100% at the
center point. With this design there is no attenuation (dip) in the center position for either audio signal,
hence "dipless."
dipole bass or dipole subwoofer system Loudspeakers. Literally "two poles," the name derives from the
physics definition: "A pair of electric charges or magnetic poles, of equal magnitude but of opposite sign
or polarity, separated by a small distance." [AHD] In dipole woofer designs the rear wave is left
untreated, and the overall system response is tuned by varying the baffle size and the system "Q." It acts
like a figure-of-eight source and thus excites room modes less than monopole woffer systems. For
detailed theory and DIY examples buy Linkwitz Labs Archive CD-ROM, the best source available
direct box Also known as a DI box, a phrase first coined by Franklin J. Miller, founder of Sescom, to (9 of 16) [10/3/04 12:29:17 AM]
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describe a device that enables a musical instrument (guitar, etc.) to be connected directly to a mic- or linelevel mixer input. The box provides the very high input impedance required by the instrument and puts
out the correct level for the mixer.
directional microphone One whose response is more sensitive to sound arriving from one direction than
another. See: unidirectional microphone
direct out Term for auxiliary outputs found on some mic preamps, mixing consoles, and
teleconferencing equipment. Direct outputs are taken before any signal processing (other than normal mic
preamp functions like gain, buffering, phantom power, bandlimiting filters, etc.), or mixing with other
channels is done, hence, normally at line-level.
direct sound Sound first arriving. Sound reaching the listening location without reflections, i.e., sound
that travels directly to the listener. See also early reflections.
disc The term used for any optical storage media. Originally popularized to refer to phonograph records.
From Latin discus, the term refers primarily to audio and video storage systems, such as compact discs,
laser discs, etc., but the advent of CD-ROMs and computer optical storage units blurs this distinction.
Compare with disk
discoidal capacitor Also known as feed-thru capacitors, they are used mainly by connector designers to
create in-line EMI/RFI filters for each pin. Constructed of ceramic dielectric, and toroidal shaped, these
capacitors help suppress electromagnetic interference by shunting the interference to ground, and if
combined with a series inductor become even more effective. The feed-thru design results in greatly
reduced self-inductance compared to standard leaded capacitors. The combination of low inductance and
high input/output isolation provides excellent shunting of EMI for frequencies up to and beyond 1 GHz.
Made by Spectrum Control, Inc., CDI, INSTEC, and others.
discreet Marked by, exercising, or showing prudence and wise self-restraint in speech and behavior.
(AHD) [You may want to be discreet when bussing someone.]
discrete Constituting a separate thing; distinct, or a set of distinct things. (AHD)
discrete Fourier transform (DFT) 1. A numerical method of calculating the coefficients of the Fourier
series from a sampled periodic signal. 2. A DSP algorithm used to determine the Fourier coefficient
corresponding to a set of frequencies, normally linearly spaced. See: Fourier theorem.
disk The term used for any magnetic storage media such as computer diskettes or hard disks. From Greek
diskos, the term refers primarily to non-audio digital data storage, but the advent of hard disk digital
audio recording systems fogs this up somewhat. Compare with disc (10 of 16) [10/3/04 12:29:17 AM]
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distance learning A specialized form of videoconferencing optimized for educational uses. Distance
learning allows students to attend classes in a location distant from where the course is being presented.
Two-way audio and video allows student and instructor interaction.
distortion Audio distortion: By its name you know it is a measure of unwanted signals. Distortion is the
name given to anything that alters a pure input signal in any way other than changing its size. The most
common forms of distortion are unwanted components or artifacts added to the original signal, including
random and hum-related noise. Distortion measures a system's linearity - or nonlinearity, whichever way
you want to look at it. Anything unwanted added to the input signal changes its shape (skews, flattens,
spikes, alters symmetry or asymmetry, even if these changes are microscopic, they are there). A spectral
analysis of the output shows these unwanted components. If a piece of gear is perfect, it does not add
distortion of any sort. The spectrum of the output shows only the original signal - nothing else - no added
components, no added noise - nothing but the original signal. See RaneNote: Audio Specifications
distribution amplifier A splitter with added features. Distribution amplifiers (usually) feature balanced
inputs and outputs with high-current line drivers (often cross-coupled) capable of driving very long lines.
dither The noise (analog or digital) added to a signal prior to quantization (or word length reduction)
which reduces the distortion and noise modulation resulting from the quantization process. Although
there is a slight increase in the noise level, spectrally shaped dither can minimize the apparent increase.
The noise is less objectionable than the distortion, and allows low-level signals to be heard more clearly.
The most popular type of dither is called TPDF. See RaneNote: Digital Dharma of Audio A/D Converters
DIY Acronym for do-it-yourself, usually referring to various hobbies, especially audio-related.
DJ mixer For a history of, see David Cross's master thesis: The History of the DJ Mixer.
DLP (digital light processing) Texas Instrument's proprietary projection display technology. The basis of
the technology is the Digital Micromirror Device (DMD) semiconductor chip, which uses an array of up
to 1.3 million hinged, microscopic mirrors (made using nano-technology) that operate as optical switches
to create a high resolution color image. See TI's DLP website.
DMD (digital micromirror device) See DLP above.
DMM (digital multimeter) See VTVM
DO (digital audio output) AES3 (and IEC 60958-4) abbreviation to be used for panel marking where
space is limited and the function of the XLR digital AES3 connector might be confused with an analog
signal connector. (11 of 16) [10/3/04 12:29:18 AM]
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Dolby Digital® Dolby's name for its format for the digital soundtrack system for motion picture
playback. Utilizes their AC-3 system of digital compression. The signal is optically printed between the
sprocket holes. Now being introduced to Home Theater on laserdisc and DVD. Dolby Digital may use
any number of primary audio delivery and reproduction channels, from 1 to 5, and may include a separate
bass-only effects channel. The designation "5.1" describes the complete channel format. Surround
decoder systems with Dolby Digital automatically contain Dolby Pro Logic processing to ensure full
compatibility with the many existing program soundtracks made with Dolby Surround encoding. No
abbreviations are to be used. See RaneNote: Home Cinema Systems
dongle Security device for protected software: a small hardware device that, when plugged into a
computer, enables a specific copy-protected program to run, the program being disabled on that computer
if the device is not present. The device is effective against software piracy.
Doppler effect [After Christian Johann Doppler, 1803-1853, Austrian physicist and mathematician
who first enunciated this principle in 1842.] 1. For an observer, the apparent change in pitch (frequency)
of a sound (or any wave) when there is relative motion between the source and the listener (or observer).
The classic example is the train phenomenon where the pitch of the whistle sounds higher approaching
and lower leaving. 2. Gave rise to the variation known as the dope-ler effect, defined as the phenomenon
of stupid ideas that seem smarter when they come at you in rapid succession. [Thanks, JF.]
DOS (pronounced "doss") (disk operating system) A software program controlling data in memory, disk
storage, running programs and I/O management.
double balanced See cables.
double-barrelled shotgun Harmonica that can be played from both sides. (Decharne)
double bass A large viola that plays one octave lower than the cello, thereby doubling the bass. Also
referred to as a Baroque doghouse for its deep tones. See: Slatford for historical details.
double-blind comparator See ABX testing
Double MS See: MSM
double precision The use of two computer words to represent each number. This preserves or improves
the precision, or correctness, of the calculated answer. For example, if the number 999 is single precision,
then 999999 is the double precision equivalent.
doubling Recording. An effect where the original signal is added to a slightly delayed version of itself.
The result is a fuller sound, giving the aural impression of more players or singers then originally
recorded. The most famous use of doubling is that done by Roger Nichols on Donald Fagen's vocals and (12 of 16) [10/3/04 12:29:18 AM]
Rane Professional Audio Reference (D)
Walter Becker's instruments in all Steely Dan recordings.
downstage Theater. The front of the stage closest to the audience, as opposed to upstage.
downward expander See: expander
Drag and Drop 1. A protocol where objects from one desktop application can be 'dragged' out of that
application, through clicking on the object with a mouse, across the desktop and 'dropped' on another
application. Most graphics operating systems use some form of Drag and Drop. (Newton) For an
example, see Drag NetGUI. 2. Not to be confused with dragon drop -- a mess crated by a fire-breathing
creature. (Thanks CD.)
drain wire A non-insulated wire in contact with parts of a cable, usually the shield(s), used for chassis or
earth grounding; in general, a ground or shield wire.
dreamt The only English word ending in the letters "mt."
DRM (Digital Rights Management) Controlling mechanisms for exchanging intellectual property in
digital form over the Internet or other electronic media. Basically, DRM is an encryption distribution
scheme with built-in payment methods. Content is encoded, and to decode it a user must do something
like supply a credit card, or provide an e-mail address, or whatever. Content owners set the conditions.
dropout An error condition in which bits are incorrect or lost from a digital medium. Also occurs with
analog tape - audio or video.
dry Recording. 1. The original recorded signal before any effects processing. 2. Any signal without
reverberation; dead. Contrast with wet.
dry circuit See below.
dry transformer Telephony. An analog audio transformer designed for AC operation only; no direct
current (DC) is allowed to flow in the primary or secondary coils. Derived from the term, dry circuit,
referring to a circuit where voice signals are transmitted but does not carry direct current. Contrast with
wet transformer.
DSD® (Direct Stream Digital®) See: SACD
DSP (digital signal processing) A technology for signal processing that combines algorithms and fast
number-crunching digital hardware, and is capable of high-performance and flexibility. (13 of 16) [10/3/04 12:29:18 AM]
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DTE (Data Terminal Equipment) 1. Within the RS-232 standard, the equipment comprising the data
source, the receiver, or both - e.g., personal computers or terminals. See: DCE. The main difference
between DTE and DCE is the wiring of pins 2 and 3, thus the need for a null modem cable when tying
two computers together. 2. CobraNet refers to DTEs as the source and sink devices on the network, i.e.,
they source and sink audio. Rane's NM 48 & NM 84 Network Mic/Line Preamps are DTE devices.
DTMF (dual tone multi-frequency) Normal everyday pushbutton touch-tone dialing system, where a
combination of two tones is used for each button pushed.
DTRSTM (digital tape recording system) Tascam's suggested term for describing their DA-88 type
digital multitrack recorders.
DTS Coherent AcousticsTM (now DTS Cinema) A competing digital soundtrack system for motion
picture playback developed by Digital Theater Systems Inc. (backed by Stephen Spielberg and Universal
Studios). Its novelties are: 1) not requiring a special projector to read digital code off the filmstrip like its
competitors; 2) using only very moderate compression (3:1 verses Dolby's 11:1); and 3) offering 20-bit
audio. The discrete digital full bandwidth six (6) channel sound is contained on a CD that is played
synchronously with the film. The synching time code is printed between the standard optical soundtrack
and the picture.
DTS-ES (DTS Extended Surround) Digital Theater System's version of THX Surround EX. DTS-ES
adds a third surround channel to the left and right surround channels in a DTS-encoded signal. Two
versions exist: straight "DTS-ES" matrix-encodes the third surround channel into the existing left and
right surround signals in a 5.1 channel source, while "DTS-ES Discrete" is a new format that adds a
separate third surround channel.
DTS Zeta DigitalTM (now DTS Consumer) Digital Theater Systems' audio compression scheme
applied to laser disc, DVD and CD technology for home theater use. Competing format with Dolby's AC3 algorithm. See RaneNote: Home Cinema Systems
dubplate or dub plate DJ. An acetate one-off version of a vinyl record. The name comes from the
Jamaican dancehall reggae scene in the early '70s where "dub" or instrumental versions of songs were
produced so the vocalist could "toast" over the "riddims" in club settings.
ducker A dynamic processor that lowers (or "ducks") the level of one audio signal based upon the level
of a second audio signal. A typical application is paging: A ducker senses the presence of audio from a
paging microphone and triggers a reduction in the output level of the main audio signal for the duration
of the page signal. It restores the original level once the page message is over. Another use is for talkover.
Dudley, Homer Inventor of the vocoder. [Dudley, H. (1939) "The Vocoder," Bell Labs Record, 17, pp.
122-126] (14 of 16) [10/3/04 12:29:18 AM]
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dummy load Any substitute device having impedance characteristics simulating those of the substituted
device. For example, see amplifier dummy load
duplex Pertaining to a simultaneous two-way independent transmission in both directions. Often referred
to as "full duplex" which is redundant. See also: half-duplex.
DVD (Officially "DVD" does not stand for anything. It used to mean "digital versatile disc" - and before
that it meant "digital video disc" also once known as hdCD in Europe.) A 12-centimeter (4.72") compact
disc (same size as audio CDs and CD-ROMs) that holds 10 times the information. Capable of holding fulllength movies and a video game based on the movie, or a movie and its soundtrack, or two versions of
the same movie - all in sophisticated discrete digital audio surround sound. The DVD standard specifies a
laminated single-sided, single-layer disc holding 4.7 gigabytes, and 133 minutes of MPEG-2 compressed
video and audio. It is backwards compatible, and expandable to two-layers holding 8.5 gigabytes.
Ultimately two discs could be bounded together yielding two-sides, each with two-layers, for a total of 17
gigabytes. There are four main versions:
DVD-Video (movies) As outlined above.
DVD-Audio (music-only) The standard is flexible, allowing for many possibilities, leaving
the DVD-player to detect which system is used and adapt. Choices include 74 minutes for 2chs at 24-bits, 192 kHz sampling, or 6-chs at 24-bits, 96 kHz, all utilizing lossless
compression (type MLP for Meridian Lossless Packing). Quantization can be 16-, 20-, &
24-bits, with sampling frequencies of 44.1, 88.2, and 176.4 kHz, as well as 48, 96, and 192
kHz all supported. [See "DVD-Audio Specifications" by Norihiko Fuchigami, Toshio
Kuroiwa, and Bike H. Suzuki, in the J. Audio Eng. Soc., Vol. 48, No. 12, December 2000,
pp. 1228-1240 for complete details.]
DVD-ROM (read-only, i.e., games and computer use)
DVD-RAM (rewritable, i.e., recording systems). Matsushita (Panasonic brand) is currently
the leader in density with 4.7 Gb and 9.4 Gb claimed for single-sided and double-sided
discs respectively, compared with 2.6 Gb and 5.2 Gb offered by standard DVD-RAM
technology. There are several competing formats:
DVD-R (Hitachi, Pioneer & Matsushita) Primary 4.7 Gb application is
peripheral drive for PCs, but is also of interest for video servers, video-disk
cameras and other consumer applications.
DVD-RW (Pioneer) Also 4.7 Gb aimed at VCR replacement.
DVD+RW or just RW (because it is not sanctioned by the DVD Forum)
(Sony, Philips & Hewlett-Packard) Originally a 3-Gbyte system, positioned
as a PC peripheral, but now expanded to a 4.7 Gbyte consumer version.
MMVF-DVD (NEC's 5.2 Gbyte Multimedia Video File Disk system) Now
officially shifted from a laboratory project to a business project. (15 of 16) [10/3/04 12:29:18 AM]
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dynamic controllers (or dynamic processors) A class of signal processing devices used to alter an audio
signal based solely upon its frequency content and amplitude level, thus the term "dynamic" since the
processing is completely program dependent. The two most common dynamic effects are compressors
and expanders, with limiters, noise gates (or just "gates"), duckers and levelers being subsets of these.
Another dynamic controller category includes exciters, or enhancers. And noise reduction units fall into a
final dynamic processor category. See RaneNote: Squeeze Me, Stretch Me: The DC 24 Users Guide
dynamic microphone A microphone design where a wire coil (the voice coil) is attached to a small
diaphragm such that sound pressure causes the coil to move in a magnetic field, thus creating an electrical
voltage proportional to the sound pressure. Works in almost the exact opposite of a dynamic loudspeaker
where an electrical voltage is applied to the voice coil attached to a large cone (diaphragm) causing it to
move in a magnetic field, thus creating a change in the immediate sound pressure. In fact, under the right
circumstances, both elements will operate as the other, i.e., a dynamic loudspeaker will act as a
microphone and a dynamic microphone will act as a loudspeaker -- although not too loud. See
electromagnetic induction.
dynamic range The ratio of the loudest (undistorted) signal to that of the quietest (discernible) signal in a
unit or system as expressed in decibels (dB). Dynamic range is another way of stating the maximum S/N
ratio. With reference to signal processing equipment, the maximum output signal is restricted by the size
of the power supplies, i.e., it cannot swing more voltage than is available. While the noise floor of the
unit determines the minimum output signal, i.e., it cannot put out a discernible signal smaller than the
noise. Professional-grade analog signal processing equipment can output maximum levels of +26 dBu,
with the best noise floors being down around -94 dBu. This gives a maximum dynamic range of 120 dB pretty impressive numbers, which coincide nicely with the 120 dB dynamic range of normal human
hearing (from just audible to uncomfortably loud). See RaneNote: Audio Specifications
dyne A unit of force, equal to the force required to impart an acceleration of one centimeter per second
per second to a mass of one gram. (AHD) Old units for sound pressure.
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e Mathematics. The base of the natural system of logarithms, having a numerical value of approximately
2.71828. (AHD) See Maor.
ear Anatomy. The vertebrate organ of hearing, responsible for maintaining equilibrium as well as sensing
sound and divided in mammals into the external ear, the middle ear, and the inner ear. [AHD]
ear buds See: IEM.
early decay time (EDT) Time (in seconds) that it takes for a signal to decay from 0 to -10 dB relative to
its steady state value.
early reflections Acoustics. The first sound that arrives at a listener is called the direct sound; the next to
arrive is the first reflected sound waves, which take a little longer to reach the listener due to traveling a
slightly longer path length. The first several reflected sound waves to reach the listener after the direct
sound are called early reflections.
ears See: IEM.
earthshine The sunlight reflected from the Earth to the moon and back again. Leonardo da Vinci was the
first person to figure out that when the Earth reflects enough light, we can see the entire moon, not just
the crescent.
EASE (Enhanced Acoustic Simulator for Engineers) A computer modeling tool distributed by RenkusHeinz for ADA (Acoustic Design Ahnert), who developed the software and introduced it in 1990 at the
88th AES Convention in Montreux.
EBU (European Broadcasting Union) An international professional society that, among other things,
helps establish audio standards.
echo 1. Acoustics A discrete sound reflection arriving at least 50 milliseconds after the direct sound, and
significantly louder than the background reverberant sound field. Contrast with reverberation. 2.
Psychoacoustics A perceptually distinct copy of the original sound; a delayed duplicate. A single echo
may be the result of multiple surface reflections. [Blesser] (1 of 8) [10/3/04 12:29:27 AM]
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echo canceller A technique using DSP(analog circuits exist, but DSP solutions are overwhelmingly
superior) that filters unwanted signals caused by echoes from the main audio source. Echoes happen in
both voice and data conversation, therefore two types of cancellers are encountered: acoustic and line.
"Acoustic" echo cancellers are used in teleconferencing applications to suppress the acoustic echoes
caused by the microphone/loudspeaker combination at one end picking up the signal from the other end
and returning it to the original end. It is similar to sound system feedback problems (where the sound
reinforcement loudspeaker is picked up by the microphone, re-amplified through the loudspeaker, only to
be picked up again by the microphone, to be re-amplified, and so on), only made much worse by the
additional time delay introduced by the telecommunication link. "Line" echo cancellers are used to
suppress electrical echoes caused by the transmission link itself. Such things as non-perfect hybrids, and
satellite systems (creating round-trip delays of about 600 ms), contribute to very annoying and disruptive
line echoes.
echoic Of or resembling an echo (AHD).
ECS (Engineered Conference Systems) Rane Corporation trademark for their teleconferencing
eddy current An electrical current induced in electrical conductors by fluctuating magnetic fields in the
conductors. The current moves contrary to the direction of the main current, just below the surface of the
material, flowing in circular motion like river eddies. First noted by Michael Faraday after his discovery
of electromagnetic induction in 1831. For a short tutorial see Eddy Current Theory - Principles Nondestructive testing based on eddy currents is a fast growing industry. Electrical currents are generated in
a conductive material by an induced alternating magnetic field. Interruptions in the flow of eddy currents,
caused by imperfections, dimensional changes or changes in the material's conductive and permeability
properties, can be detected with the proper equipment.
Edison effect In 1883, Thomas Edison noticed that certain materials, when heated by a filament in a
vacuum, emitted electrons that could be attracted to an electrode held at a positive potential with respect
to the emitter. This became known as the Edison effect and according to Edison, was discovered by
accident when experimenting with his new invention, the incandescent lamp. Twenty years later, this
effect became the basis for inventing the vacuum tube.
Edison plug An ordinary household plug with two flat blades and a ground pin.
EDT See: early decay time.
EEPROM or E2PROM (electrically erasable programmable read-only memory) A version of readonly memory that can be electrically erased and reprogrammed by the designer. Differentiated from
standard EPROM (one "E") which requires ultraviolet radiation for erasure. (2 of 8) [10/3/04 12:29:27 AM]
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effects loop A mixer term used to describe the signal path location where an external (outboard) signal
processor is connected. The loop consists of an output Send jack connecting to the effects box input, and
an input Return or Receive jack that comes from the effects box output. This is the preferred term when
two separate 1/4", or other connectors are provided to patch in an outboard processor using separate
cables for send and receive. These jacks are usually unbalanced, but could be balanced. A stereo effects
loop requires four jacks. Compare with insert loop
EFP (electronic field production) mixer Pretentious equivalent for ENG mixer
EIA (Electronic Industries Alliance) Founded in 1924 as the Radio Manufacturers Association (RMA),
The EIA is a private trade organization made up of manufacturers which sets standards for voluntary use
of its member companies (and all other electronic manufacturers), conducts educational programs, and
lobbies in Washington for its members' interests.
EIA-422 See RS-422
EIA-485 See RS-485
eigentone (from German eigen meaning "self" or "own") See room mode
EIN (equivalent input noise) Output noise of a system or device referred to the input. Done by modeling
the object as a noise-free device with an input noise generator equal to the output noise divided by the
system or device gain. See RaneNote: Audio Specifications
Elco plug See connectors.
electone (electronic tone) A trade-marked symbol of the Yamaha Corporation; the brand name of
Yamaha's organ instrument line.
electret microphone A microphone design similar to that of condenser mics except utilizing a
permanent electrical charge, thus eliminating the need for an external polarizing voltage. This is done by
using a material call an electret [acronym for electricity + magnet] that holds a permanent charge (similar
to a permanent magnet, i.e., a solid dielectric that exhibits persistent dielectric polarization). Because
electret elements exhibit extremely high output impedance, they often employ an integral built-in
impedance converter (usually a single JFET) that requires external power to operate. This low voltage
power is often supplied single-ended over an unbalanced connection, or it may operate from standard
phantom power. Electret technology was co-pioneered by Jim West and Gerhard Sessler in the 1960s at
Bell Labs. Their original research into polymers (an electrical analogy of a permanent magnet) led to
electret transducers. (3 of 8) [10/3/04 12:29:27 AM]
Rane Professional Audio Reference (E)
electromagnetic induction The generation of an electromotive force (voltage) and current in a circuit or
material by a changing magnetic field linking with that circuit or material. Electricity and magnetism are
kinfolk and form the foundation of audio transducers found at both ends of any audio chain: dynamic
microphones and loudspeakers with voice coils. The principle is beautifully simple: if you pass a coil of
wire through a magnetic field, electricity is generated within the coil (dynamic microphone), and if you
pass electricity through a coil of wire (voice coil), a magnetic field is generated. Move a magnet, create a
voltage; apply a voltage, create a magnet. This is the essence of all electromechanical objects.
electronic music Glossary of terms.
electrostatic loudspeaker See loudspeaker
electrostatic microphone See condenser microphone
elephant teeth Piano keys. (Decharne)
elliptic filters or elliptic-function filters also called Cauer filters after network theorist Wilhelm Cauer.
A filter having an equiripple passband and an equiminima stopband. [IEEE] Butterworth filters are allpole types, while elliptic filters have zeros as well as poles at finite frequencies. The location of the poles
and zeros creates equiripple behavior in the passband similar to Chebyshev filters. Finite transmission
zeros in the stopband reduce the transition region so that extremely sharp roll-off rates result; however
the improved performance is obtained at the expense of return lobes ("bounce") in the stopband.
EMC Directive (ElectroMagnetic Compatibility) 1. A directive issued by the European Commission
aimed at establishing product compatibility within the EU (European Union). Article 1.4 defines
electromagnetic compatibility as the ability of an electrical and electronic appliance, equipment or
installation containing electrical and/or electronic components to function satisfactorily in its
electromagnetic environment (immunity requirement) without introducing intolerable electromagnetic
disturbances to anything in that environment (emission requirement). 2. Due to the significant increases
in development time and product costs imposed by the EMC Directive, many believe the initials really
stand for "eliminate minor companies." [Thanks DC.]
EMD (electronic music distribution) Distributing digital music files (compressed using MP3, AAC, AC3, etc.) from a server to a client.
EMF (electromotive force) Electronics. Voltage. See volt; also back-emf
EMI (electromagnetic interference) A measure of electromagnetic radiation from equipment.
emitter follower See buffer amplifier (4 of 8) [10/3/04 12:29:27 AM]
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EMP (Experience Music Project) Paul Allen's (co-founder of Microsoft) interactive music museum,
located in Seattle, that celebrates and explores creativity and innovation in American popular music as
exemplified by rock 'n' roll. [Very cool place ... come visit sometime.]
empath 1. One who practices empathy, i.e., a person who strongly identifies with and understands
another's situation, feelings, and motives. 2. A DJ performance mixer combining the vision of
Grandmaster Flash and Rane technology.
ENG (electronic news gathering) mixer Portable battery-powered mixer accommodating at least two or
three mic inputs, used in the field to record speech and outdoor sound effects. Some specialized models
have built-in telephone line interfacing.
enhancers See: exciters
ENOB (effective number of bits) A figure of merit for A/D data converters useful in specifying a
converter's real AC accuracy and performance. We all know that the data sheet says it's 24 bits, but what
is it really? For a perfect sine wave, it can be approximated from the SINAD measurement by subtracting
1.76 from the SINAD (dB) and then dividing by 6.02. (For down-and-dirty quick calculations just divide
the SINAD by 6 and you'll be in the ballpark.) For example, if a 24-bit A/D converter has a real world
measured SINAD = 100 dB, then it has an ENOB equal to 16, nowhere near the claimed 24 bits.
envelope Waves. The boundary of the family of curves obtained by varying a parameter of the wave.
envelope control Synthesizers. A voltage controlling pitch and volume to create a distinctive contour
envelope delay See group delay.
eponym A person whose name is or is thought to be the source of the name of something, such as a city,
country, or era. For example, Romulus is the eponym of Rome. (AHD)
EQ (equalizer) A class of electronic filters designed to augment or adjust electronic or acoustic systems.
Equalizers can be fixed or adjustable, active or passive. Indeed, in the early years of telephony and
cinema, the first equalizers were fixed units designed to correct for losses in the transmission and
recording of audio signals. Hence, the term equalizer described electronic circuits that corrected for these
losses and made the output equal to the input. Equalizers commonly modify the frequency response of
the signal passing through them; that is, they modify the amplitude versus frequency characteristics.
There are also fixed equalizers that modify the phase response of the transmitted signals without
disturbing the frequency content. These are referred to as all-pass, phase-delay, or signal-delay (5 of 8) [10/3/04 12:29:27 AM]
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equalizers. See RaneNote: Exposing Equalizer Mythology, RaneNote: Operator Adjustable Equalizers,
and RaneNote: Signal Processing Fundamentals.
equal-tempered scale or equal temperment Music. Today's normal musical scale, it divides a musical
octave into twelve equal parts (semitones), i.e., each is 2 1/12 above the other. Compare: just
equivalent input noise See EIN
Eric "Hoss" Cartwright's given name -- "Hoss" was a nickname ... ... this, for all you Jeopardy! fans.
error correction A method using a coding system to correct data errors by use of redundant data within
a data block. Often data is interleaved for immunity to burst errors. Corrected data is identical to the
ESR (effective series resistance) Capacitors. The sum of many resistive losses in a capacitor. It includes
resistance of the dielectric, plate material, electrolytic solution, and terminal leads at one specified
frequency and acts like a resistor in series with a perfect capacitor. It is measured in ohms and is the real
part of impedance.
EST (Electronic Systems Technician) A consortium for electronic systems technician training.
ESTA (Entertainment Services & Technology Association) A non-profit trade association representing
the North American entertainment technology industry.
ether From a Greek word meaning "upper air," a term used in early physics (based on ancient beliefs), a
magical medium thought to explain the propagation of electromagnetic waves.
Ethernet A local area network (LAN), originally developed by Xerox in 1973 (the name was coined by
its inventor Bob Metcalfe [who went on to found 3Com in 1979] after the old science term ether), used
for connecting computers, printers, workstations, terminals, etc., now extended to include audio and
video using CobraNet technology. Ethernet operates over twisted-pair, coaxial cable, or fiber optic cable
at various speeds designated "10Base-T" up to 10 megabits/sec (Mbps), "100Base-T", a.k.a. Fast
Ethernet, up to 100 Mbps, and "1000Base-T" up to 1 gigabit/sec, or 1000 Mbps, a.k.a. Gigabit Ethernet
(GE) [uses all 8 conductors and can be up to 100 meters long], and now, talk of moving beyond 10
Gbits/s, known simply as 10-Gbit Ethernet. (The number in the front designates the speed in
megabits/second. "Base" indicates the network is baseband. The letter following determines the type of
cable and its requirements. 10Base-T, for example is unshielded twisted-pair, using a star topology, and
1000Base-F uses fiber cable. ) Other Ethernet designators include: (6 of 8) [10/3/04 12:29:27 AM]
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1000Base-CX A standard for GE connectivity where the "C" means copper and "X" is a
1000Base-SX ("S" for short wavelength laser) for laser fiber cabling based on the Fiber
Channel signaling specification for multimode fiber only.
1000Base-LX ("L" for long wavelength laser) for laser fiber cabling also based on the
Fiber Channel signaling specification for multimode or single-mode fiber.
1000Base-LH ("LH" for long haul) for a multivendor specification (each vendor has a set
of transceivers covering different distances). While not an IEEE standard, the vendors are
working to interoperate with IEEE 1000Base-LX equipment using the gigabit interface
connector (GBIC) multivendor specification in order to provide a common form factor
and greater flexibility.
Further details available at Network Information
Euroblocks Shortened form for European style terminal blocks. See connectors.
exciters (or enhancers) A term referring to any of the popular special-effect signal processing products
used primarily in recording and performing. All exciters work by adding harmonic distortion of some
sort - but harmonic distortion found pleasing by most listeners. Various means of generating and
summing frequency-dependent and amplitude-dependent harmonics exist. Both even- and odd-ordered
harmonics find favorite applications. Psychoacoustics teaches that even-harmonics tend to make sounds
soft, warm and full, while odd-harmonics tend to make things metallic, hollow and bright. Lower-order
harmonics control basic timbre, while higher-order harmonics control the "edge" or "bite" of the sound.
Used with discrimination, harmonic distortion changes the original sound dramatically, more so than
measured performance might predict.
expander A signal processing device used to increase the dynamic range of the signal passing through
it. Expanders complement compressors. For example, a compressed input dynamic range of 70 dB might
pass through a expander and exit with a new expanded dynamic range of 110 dB. [Long answer: Just like
compression, what "expansion" is and does has evolved significantly over the years. Originally
expanders were used to give the reciprocal function of a compressor, i.e., it undid compression. Anytime
audio was recorded or broadcast it had to be compressed for optimum transfer. Then it required an
expander at the other end to restore the audio to its original dynamic range. Operating about the same
"hinge" point and using the same ratio setting as the compressor, an expander makes audio increases and
decreases bigger. From this sense came the phrase that "expanders make the quiet sounds quieter and the
loud sounds louder." Modern expanders usually operate only below a set threshold point (as opposed to
the center hinge point), i.e., they operate only on low-level audio. The term downward expander or
downward expansion evolved to describe this type of application. ( The term upward expander is
sometimes used to refer to expanders operating only on high-level signals, i.e., increasing dynamic range (7 of 8) [10/3/04 12:29:27 AM]
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above threshold.) The most common use is noise reduction. For example, say, an expander's threshold
level is set to be just below the smallest vocal level being recorded, and the ratio control is set for 3:1.
What happens is this: when the vocals stop, the "decrease below the set-point" is the change from signal
(vocals) to the noise floor (no vocals), i.e., there has been a step decrease from the smallest signal level
down to the noise floor. If that step change is, say, -10 dB, then the expander's output will be -30 dB
(because of the 3:1 ratio, a 10 dB decrease becomes a 30 dB decrease), thus resulting in a noise reduction
improvement of 20 dB. See RaneNote: The DC 24 Users Guide, RaneNote: Signal Processing
Fundamentals, and RaneNote: Good Dynamics Processing.
exponent The component of a floating-point number that normally signifies the integer power to which
the radix is raised in determining the value of the represented number (IEEE-100). For example if radix
=10 (a decimal number), then the number 183.885 is represented as mantissa = 1.83885 and exponent = 2
(since 183.885 = 1.83885 x 102).
exponential horn Loudspeakers. A horn design characterized by having an exponentially increasing
cross-sectional area.
"Expressman Blues" The first rock and roll song, recorded May 17, 1930 by "Sleepy" John Estes, Yank
Rachel and Hammy Nix. (McCleary)
extensible Of or relating to a programming language or a system that can be modified by changing or
adding features. Capable of being extended: AES24 is an extensible protocol.
eye pattern An oscilloscope display of the received voltage waveform in a transmission system. So
named because portions of the display take on a human eye-like shape. The eye pattern gives important
information. An eye pattern is obtained when a high speed transmission system outputs a long
pseudorandom bit sequence. A sampling oscilloscope is used to observe the output such that the scope is
triggered to sample on every fourth or eighth pseudorandom clock cycle, and every sample point is
plotted on the screen. (The pseudorandom digital data signal from a receiver is repetitively sampled and
applied to the vertical input, while the data rate is used to trigger the horizontal sweep.) The picture
obtained is a superposition of ones and zeros output. The horizontal "fatness" of the lines indicates the
amount of jitter and the rise and fall times is measured from the crossing points. See Siemon publication
Data Throughput Validation: Making Every Bit Count for an example and more details.
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42V PowerNet The official name for the new 42 V automotive electrical power system. The value of 42
volts comes from a tripling of the normal 12 V car battery to 36 volts which measures 42 volts when
5.1 surround sound The digital audio multichannel format developed by the Moving Picture Experts
Group (see: MPEG) for digital soundtrack encoding for film, laserdiscs, videotapes, DVD, and HDTV
broadcast. The designation "5.1" (first proposed by Tom Holman of THX fame) refers to the five
discrete, full bandwidth (20-20 kHz) channels - left, right, & center fronts, plus left & right surrounds and the ".1" usually refers to the limited bandwidth (20-120 Hz) subwoofer channel, but can also refer to
a special effects/feature channel. Terminology used by both Dolby Digital and DTS Consumer (the home
version of their theater Coherent Acoustics system).
fader A control used to fade out one input source and fade in another. The fading of a single source is
called attenuation and uses an attenuator.
Fahrenheit Abbr. F Of or relating to a temperature scale that registers the freezing point of water as 32
°F and the boiling point as 212 °F, under normal atmospheric pressure. (AHD) [In scientific and
technical contexts temperatures are now usually measured in degrees Celsius rather than Fahrenheit.]
[After Gabriel Daniel Fahrenheit.]
Fahrenheit, Gabriel Daniel (1686-1736) German-born physicist who invented the mercury
thermometer (1714) and devised the Fahrenheit temperature scale. (AHD)
FAQ (frequently asked question) Acronym commonly seen on bulletin boards, Internet Web sites, and
corporate information centers. By compiling FAQ lists (FAQs), organizations significantly reduce time
spent repeatedly answering the same questions.
Faraday, Michael (1791-1867) British physicist and chemist who discovered electromagnetic induction
(1831) and proposed the field theory later developed by Maxwell and Einstein. (AHD) After announcing
that a new source of energy was possible by moving a magnet in a coil of wire, many declared him a
fraud. Faraday responded with his memorable words: "Nothing is too wonderful to be true, if it be
consistent with the laws of nature." See Faraday's Magnetic Field Induction Experiment (1 of 9) [10/3/04 12:29:35 AM]
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far end Teleconferencing term meaning the distant location of transmission; the other end of the
telephone line, as opposed to your end (known as the near end).
far-end crosstalk Crosstalk that is propagated in a disturbed channel in the same direction as the
propagation of the signal in the disturbing channel. The terminals of the disturbed channel, at which the
far-end crosstalk is present, and the energized terminals of the disturbing channel, are usually remote
from each other.
far field or far sound field The sound field distant enough from the sound source so the SPL decreases
by 6 dB for each doubling of the distance from the source (inverse square law). Contrast with near field.
Fast Ethernet See: Ethernet
fat Recording slang. Informal phrase for heavily processed audio, usually featuring lots of reverb,
chorusing, or doubling. Also seen as phat sound.
fax on demand One of the terms for the process of ordering fax documents from remote machines via
telephone, using a combination of voice processing and fax technologies. Also called fax-back.
fax-back See fax on demand.
FEA See Finite Element Analysis
feedback See acoustic feedback.
feedback The longest word in the English language that uses all the letters "A" through "F." [Thanks,
Brad, for being so observant while playing Trivial Pursuit™.]
feedback suppressor An audio signal processing device that uses automatic detection to determine
acoustic feedback frequencies and then positions notch filters to cancel the offending frequencies. Other
methods us continuous frequency shifting (a very small amount) to prevent frequency build up and
feedback before it happens.
feedback troxelator Faster than an exterminator. More powerful than an eliminator. Able to leap over
an obliterator in a single sample --- 'Look, up in the sky,' 'It's a bird,' 'It's a plane,' 'It's The Troxelator ...,'
Rane's proprietary feedback suppressor technology developed by and named after Dana Troxel, one of
their senior design engineers, who proclaims: "I AM THE TROXELATOR."
FDDI (fiber distributed data interface) An ANSI standard describing a 100 megabytes/sec (MBps) fiber
optic LAN; now also specified for twisted-pair use. (2 of 9) [10/3/04 12:29:35 AM]
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femto- Prefix for one thousandth of one trillionth (10-15), abbreviated f.
ferrite bead Electronic component. A small toroidal shaped part made from a mixture of iron, nickel and
zinc oxides used to suppress EMI in audio and other electronic equipment. Usually seen on the inputs
and outputs of equipment, ferrite beads act electrically like an inductor in series with a resistor. For more
details see: "The Use of Ferrites in EMI Suppression" by Steward.
FET (field-effect transistor) A three-terminal transistor device where the output current flowing between
the source and drain terminals is controlled by a variable electric field applied to the gate terminal. The
gate design determines the type of FET: either JFET (junction FET) or MOSFET (metal-oxide
semiconductor FET). Each type has two polarities: positive, or p-channel devices, and negative, or nchannel devices. In a JFET device the gate forms a true semiconductor junction with the channel, while
in a MOSFET device the gate is insulated from the channel by a very thin (typically less than the
wavelength of light) layer of glass (silicon dioxide) and the gate is either metal or doped silicon
(polysilicon), hence the acronym metal-oxide semiconductor.
FFT (fast Fourier transform) 1. Similar to a discrete Fourier transform except the algorithm requires the
number of sampled points be a power of two. 2. A DSP algorithm that is the computational equivalent to
performing a specific number of discrete Fourier transforms, but by taking advantage of computational
symmetries and redundancies, significantly reduces the computational burden. [It is believed Cornelius
Lanczos of the Boeing Co. in the 1940's first described the FFT.]
fiber optics The technology of using glass fibers to convey light and modulated information. Short
distances (typically less than 150 feet) use plastic fibers, while long distances must use glass fibers. See
field Video. One half of a complete video scanning cycle, equaling 1/60 second, or 16.67 milliseconds
for NTSC, and 1/50 second, or 20 milliseconds for PAL/SECAM.
film sound glossary See Larry Blake's Film Sound Glossary; find out what a "binky" is.
filter Any of various electric, electronic, acoustic, or optical devices used to reject signals, vibrations, or
radiation of certain frequencies while passing others. Think sieve: pass what you want, reject all else. For
audio use the most common electronic filter is a bandpass filter, characterized by three parameters:
center frequency, amplitude (or magnitude), and bandwidth. Bandpass filters form the heart of audio
graphic equalizers and parametric equalizers.
Finite Element Analysis Abbr. FEA A computer-based numerical technique for calculating the strength
and behavior of engineering structures. See Peter Budgell's Finite Element Analysis and Optimization
Introduction (3 of 9) [10/3/04 12:29:35 AM]
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FIR (finite impulse-response) filter A commonly used type of digital filter. Digitized samples of the
audio signal serve as inputs, and each filtered output is computed from a weighted sum of a finite number
of previous inputs. An FIR filter can be designed to have linear phase (i.e., constant time delay,
regardless of frequency). FIR filters designed for frequencies much lower that the sample rate and/or
with sharp transitions are computationally intensive, with large time delays. Popularly used for adaptive
Firefly See ZigBee
Firewire See: IEEE 1394
firkytoodle An English word no longer in print (except here) meaning to engage in intimate physical
affection, as a prelude to sexual intercourse; foreplay (17th to 19th century).
firmware Computer read-only code (files) residing inside DSP and microprocessor ICs that controls the
hardware response to software instructions -- the liaison between software and hardware.
fishpaper An insulating paper, often fiber- or oilcloth-like, used in the construction of transformers and
coils. [Historical Note: EP Coughlin of LMC Plasticsource writes: "Although my roots go back in fiber
to 1959 I have never seen any hard copy evidence noting the origin of the name 'fishpaper.' My initial
experience in the fiber industry was with Taylor Fibre Company and the owner claimed roots back to
Thomas Taylor of England who is credited with 'inventing' vulcanized fiber. Original patent was in Great
Britain in 1859 and Thomas Taylor received a US patent in 1872 titled 'Improvements in the treatment of
paper and paper-pulp.' The major use for vulcanized fiber eventually was in the electrical insulation field
but, obviously, requirements for same did not exist in 1859. Although anecdotal, John Taylor
(owner/founder of The Taylor Fibre Company) claimed that vulcanized fiber's initial use was in
England's fish markets as table / bin liners. The resistance to fish oil and tearing of vulcanized fiber
makes this a very plausible story."]
fixed-point A computing method where numbers are expressed in the fixed-point representation system,
i.e., one where the position of the "decimal point" (technically the radix point) is fixed with respect to
one end of the numbers. Integer or fractional data is expressed in a specific number of digits, with a radix
point implicitly located at a predetermined position. Fixed-point DSPs support fractional arithmetic,
which is better suited to digital audio processing than integer arithmetic. A couple of fixed-point
examples with two decimal places are 4.56 and 1789.45.
flanging Originally, "flanging" was achieved using two reel-to-reel tape recorders playing the same
program, in synchronization, with their outputs summed together. By alternately slowing one machine,
then the other, different phase cancellations occurred in the summation process. The "slowing down" was
done simply by pressing against the flanges of the tape reels, hence the original term "reel flanging,"
soon shortened to just "flanging." Since the two identical signals would alternately add and subtract due (4 of 9) [10/3/04 12:29:35 AM]
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to the introduced phase (timing) difference, the audible effect was one of a sweeping comb filter. It was
described as a "swishing" or "tunneling" sound. Soon electronic means were devised to mimic true "reel
flanging" by using delay lines and mixing techniques. Adding a low-frequency oscillator to modulate the
audio delay line's clock signal created a sweeping effect, much like a jet airplane taking off. The best
flangers used two delay lines. Compare with: phaser
Fleming, Sir John Ambrose (1849-1945) British electrical engineer and inventor known for his work on
electric lighting, wireless telegraphy, and the telephone. He invented and patented the first tube, a diode
(which he called a thermionic valve, he used for signal detection (although Edison technically developed
the first tube with a version of his light bulb).
Fletcher-Munson Curves In the '30s, researchers Fletcher and Munson first accurately measured and
published a set of curves showing the human's ear's sensitivity to pure tone loudness verses frequency
("Loudness, its Definition Measurement and Calculation," J. Acoust. Soc. Am., vol. 5, p 82, Oct. 1933).
They conclusively demonstrated that human hearing is extremely dependent upon loudness. The curves
show the ear most sensitive to pure tones in the 3 kHz to 4 kHz area. This means sounds above and
below 3-4 kHz must be louder in order to be heard just as loud. For this reason, the Fletcher-Munson
curves are referred to as "equal loudness contours." They represent a family of curves from "just heard,"
(0 dB SPL) all the way to "harmfully loud" (130 dB SPL), usually plotted in 10 dB loudness increments.
D. W. Robinson and R. S. Dadson revised the curves in their paper, "A Redetermination of the EqualLoudness Relations for Pure Tones," Brit. J. Appl. Phys., vol. 7, pp. 156-181, May 1956. These curves
supersede the original Fletcher-Munson curves for all modern work with pure tones. Robinson &
Dadson curves are the basis for ISO: "Normal Equal-Loudness Level Contours," ISO 226:1987 -- the
current standard.
Users of either of these curves must clearly understand that they are valid only for pure tones in a free
field, as discussed in the following by Holman & Kampmann. This specifically means they do NOT
apply to noise band analysis or diffused random noise for instance, i.e., they have little relevance to the
real audio world. A good overview is T. Holman and F. Kampmann, "Loudness Compensation: Use and
Abuse," J. Audio Eng. Soc., vol. 26, no. 7/8, pp. 526-536, July/August 1978.
For real audio use, the Steven's curves are more applicable: S. S. Stevens, "Perceived Level of Noise by
Mark VII and Decibels (E)," J. Acoust. Soc. Am., vol. 51, pp. 575-601, 1972. [Used to create ISO
532:1975 and ASA S3.4-1980] See Holman & Kampmann above for discussion.
flicker noise or 1/f noise Noise whose amplitude varies inversely with frequency. Mainly used in solidstate physics to describe noise with 1/f behavior, such as the noise resulting from impurities in the
conducting channel, generation and recombination noise due to base current in transistors, etc. Pink noise
has a 1/f characteristic so the two terms are often interchanged, however when used to describe
semiconductor noise (in op amps for instance) it is uniquely a low-frequency phenomena occurring
below 2 kHz, while in audio, pink noise is wideband to 20 kHz. (5 of 9) [10/3/04 12:29:35 AM]
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floating-point A computing method where numbers are expressed in the floating-point representation
system, i.e., one where the position of the decimal point does not remain fixed with respect to one end of
numerical expressions, but is regularly recalculated. A floating-point number has four parts: sign,
mantissa, radix, and exponent. The sign indicates polarity so it is always 1 or -1. The mantissa is a
positive number representing the significant digits. The exponent indicates the power of the radix (i.e.,
the number base, usually binary 2, but sometimes hexadecimal 16). A common example is the "scientific
notation" used in all science and mathematics fields. Scientific notation is a floating point system with
radix 10 (i.e., decimal). See FLOPS
floating unbalanced line A quasi-balanced output stage consisting of an unbalanced output connected to
the tip of a ¼" TRS (tip-ring-sleeve) jack through an output resistor (typically in the 50-300 ohms range).
An equal valued resistor is used to tie the ring terminal to signal ground. The sleeve connection is left
open or "floating." Thus, from the receiver's viewpoint, what is "seen" are two lines of equal impedance,
used to transfer the signal. In this sense, the line is 'balanced," although only one line is actually being
driven. Leaving the sleeve open, guarantees that only one end of the shield (the receiving end) will be
grounded. A practice that unbalanced systems often require. For trouble free interconnections, balanced
lines are always the preferred choice.
floobydust A contemporary made-up term, one meaning being derived from the archaic Latin
miscellaneus, whose disputed history springs from Indo-European roots, probably finding Greek origins
(influenced, of course, by Egyptian linguists) -- meaning a mixed bag, or a heterogeneous motley mixed
varied assortment. Popularized within the audio community when borrowed and used by the author of
this web page as a chapter title in the National Semiconductor Audio Handbook, first published in 1976.
FLOPS (floating-point operations per second) A measure of computing power.
flutter 1. Analog Recording. Any significant variation from the designed study rotational speed of a
recording or playback mechanism, e.g., turntables and analog tape recorders (typically at 5-10 Hz rate).
Heard as rapid fluctuation in pitch when played back. Compare with wow. 2. Telecommunications. Any
rapid variation of signal parameters, such as amplitude, phase, and frequency.
flux Physics. The lines of force found in an electric or magnetic field.
FOH Abbreviation for front of house, used to describe the main mixer usually located in the audience for
sound reinforcement systems. Meant to differentiate the main house mixer from the monitor mixer
normally located to the side of the stage.
foldback The original term for monitors, or monitor loudspeakers, used by stage musicians to hear
themselves and/or the rest of the band. The term "monitors" has replaced "foldback" in common practice (6 of 9) [10/3/04 12:29:35 AM]
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Foley A term synonymous with film sound effects. A recording studio Foley stage is where the sound
effects are generated in synch with the moving picture. Named after Jack Foley, who invented sound
effects for film sound while working for Universal. He simultaneously added music and effects to the
previously silent film "Showboat" and the first "Foley" session was born.
follower Shortened form for a number of electronic circuit buffer amplifiers named voltage followers,
cathode followers, emitter followers, etc.
foreground music Officially music with (or without) lyrics and performed by the original artist. Used
where it is believed people will pay attention to it. Contrast with background music.
formant Any of several frequency regions of relatively great intensity in a sound spectrum, which
together determine the characteristic quality of a vowel sound. [AHD] Formants are what you emphasis
in a sound system (or hearing aid) to improve intelligibility.
forward masking See: temporal masking
Fourier analysis Mathematics. Most often the approximation of a function through the application of a
Fourier series to periodic data, however it is not restricted to periodic data. [The Fourier series applies to
periodic data only, but the Fourier integral transform converts an infinite continuous time function into
an infinite continuous frequency function, with perfect reversibility in most cases. In this sense, it is not
an approximation. The DFT and FFT are examples of the Fourier series, but are not approximations
either unless the time data is an approximation itself, such as for sampled data systems, which introduces
sampling errors.]
Fourier, Baron Jean Baptiste Joseph (1768-1830) French mathematician and physicist who formulated
a method for analyzing periodic functions and studied the conduction of heat. (AHD)
Fourier series Application of the Fourier theorem to a periodic function, resulting in sine and cosine
terms which are harmonics of the periodic frequency. [After Baron Jean Baptiste Joseph Fourier.]
Fourier theorem A mathematical theorem stating that any function may be resolved into sine and cosine
terms with known amplitudes and phases.
Fourier transform A circuit analysis technique that decomposes or separates a waveform or function
into sinusoids of different frequency which sum to the original waveform. It identifies or distinguishes
the different frequency sinusoids and their respective amplitudes (Brigham, E. Oren, The Fast Fourier
Transform and Its Applications, Englewood Cliffs, NJ: Prentice-Hall, Inc., 1988.)
FPGA (field-programmable gate array) A programmable logic device which is more versatile (i.e.,
much larger) than traditional programmable devices such as PALs and PLAs. (7 of 9) [10/3/04 12:29:35 AM]
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frame One complete video scanning cycle, equals two fields for NTSC and PAL/SECAM.
frammel Loudspeakers. In arrays it is sometimes necessary to separate and angle the cabinets a small
amount to reduce phase interference. This is often done using a narrow wood strip called a frammel. [For
reasons I cannot determine. If you know the origin of this word, write me.]
free field or free sound field A sound field without boundaries or where the boundaries are so distant as
to cause negligible reflections over the frequency range of interest. Note that if the boundaries exist but
completely absorb the sound then a virtual free field is created, thus anechoic chambers are used to
measure loudspeakers.
frequency 1. The property or condition of occurring at frequent intervals. 2. Mathematics. Physics. The
number of times a specified phenomenon occurs within a specified interval, as: a. The number of
repetitions of a complete sequence of values of a periodic function per unit variation of an independent
variable. b. The number of complete cycles of a periodic process occurring per unit time. c. The number
of repetitions per unit time of a complete waveform, as of an electric current. (AHD)
frequency response Audio electronics. It connotes amplitude-frequency response and quantifies a
device's maximum and minimum frequency for full-output response. The electrical passband of an audio
device. The measure of any audio device's ability to respond to a sine wave program, and therefore is a
complex function measuring gain and phase shift (see phasor). It is used to express variation of gain,
loss, amplification, or attenuation as a function of frequency, normally referred to a standard 1 kHz
reference point.
full duplex Redundant term. See: duplex
full-wave rectification Term used to describe a rectifier that inverts the negative half-cycle of the input
sinusoid so that the output contains two half-sine pulses for each input cycle. (IEEE)
fuzzy clustering Mathematics. Analysis technique where complex problems are divided into groups or
"clusters" for easier understanding. When the division between clusters is not sharp then you have
"fuzzy" clusters that more accurately model real life situations. The importance to pro audio comes from
it's use in modeling acoustic fields to predict SPL and other phenomena (for instance see: Bharitkar,
Sunil and Chris Kyriakakis, "A Cluster Centroid Method for Room Response Equalization at Multiple
FX unit Slang for "effects unit." (8 of 9) [10/3/04 12:29:35 AM]
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gack Live audio. Popular slang: 1. To pretend to play a musical instrument, especially guitar. 2. An
excessive or disordered collection of miscellaneous gear. [Thanks Bink!]
gain The amount of amplification (voltage, current or power) of an audio signal, usually express in units
of dB (i.e., the ratio of the output level to the input level). For example, amplifying a voltage signal by a
factor of two is stated as a voltage gain increase of 6 dB. [Historical Usage Note: originally the terms
'gain/loss' were restricted to power use only, and 'amplify/attenuate' were used for voltage and current -although I can find no historical explanation for this arbitrary split, and no existing standards can be
found that continue to make such a distinction. It is interesting to add that conformity with such a narrow
definition of 'amplification' says that the original manufacturers misnamed their products: they should
have been called a 'gainifier' -- not an 'amplifier.' According to the true believers a 'power amplifier' is a
contradiction since you cannot 'amplify' power, only 'gainify' it. 'Power gainifier' is the correct term
according to them.]
gain riding Recording term. The act of constantly monitoring and adjusting as necessary the gain of a
recording process to prevent overloading the medium.
gain stage Any of several points in an electrical circuit where gain is taken (applied).
gain suppression See suppression.
GAL® (generic array logic) Registered trademark of Lattice Semiconductor for their invention of
EEPROM-based low-power programmable logic devices.
gang, ganged, ganging To couple two or more controls (analog or digital) mechanically (or
electronically) so that operating one automatically operates the other, usually applied to potentiometers
(pots). The volume control in a traditional two-channel hi-fi system is an example of a ganged control,
where it is desired to change the gain of two channels by the same amount, and now in home theater and
DVD-audio applications, used to change 6 or more channels simultaneously.
gap Recording. The space between opposite poles of a recording or playback head in a magnetic tape
recorder. (1 of 5) [10/3/04 12:29:43 AM]
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gate See: noise gate
gated or gated-on Teleconferencing. Term referring to microphone inputs on an automatic mic mixer
that turns off (close) after speech stops. Contrast with last-on.
gauss The centimeter-gram-second unit of magnetic flux density, equal to one Maxwell (one line of flux)
per square centimeter. [After Gauss, Karl Friedrich.] (AHD)
Gauss, Karl Friedrich (1777-1855). German mathematician and astronomer known for his
contributions to algebra, differential geometry, probability theory, and number theory. (AHD)
GBIC (gigabit interface connector) See Ethernet
GE (gigabit Ethernet) See Ethernet
Generation X The tenth generation of Americans since 1776. [From Roman numeral X meaning 10.]
See Beat Generation
getter A small amount of material added to a chemical or metallurgical process to absorb impurities. In
vacuum tubes it is a small cup or holder, containing a bit of a metal that reacts with oxygen strongly and
absorbs it. In most modern glass tubes, the getter metal is barium, which oxidizes very easily forming
white barium oxide. This oxidization removes any oxygen remaining after vacuumization.
gibi Symbol Gi New term standardized by the IEC as Amendment 2 to IEC 60027-2 Letter Symbols to be
Used in Electrical Technology to signify binary multiples of 1,073,741,824 (i.e., 2E30). Meant to
distinguish between exact binary and decimal quantities, i.e., 1,073,741,824 verses 1,000,000,000. For
example, it is now 16 gibibits, abbreviated 16 Gib, not 16 gigabits or 16 Gb.
giga- A prefix signifying one billion (10E9), abbreviated G.
gigabyte Popular term meaning a billion bytes but should be gibibyte meaning 2E30 bytes. See: gibi.
GIGO (garbage in garbage out) Popular acronym used by programmers to indicate that incorrect
information sent to a system generally results in incorrect information received from it.
glass Popular jargon referring to glass fiber optic interconnection, or fiber optics in general.
glockenspiel A percussion instrument with a series of metal bars tuned to the chromatic scale and played
with two light hammers. (AHD) (2 of 5) [10/3/04 12:29:43 AM]
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gobble pipe Saxophone. (Decharne)
Goddard, Robert Hutchings (1882-1945) See Roswell, NM.
Golden Ratio or Golden Rectangle See: phi.
GPIB (general purpose interface bus) See: IEEE-488.
gramophone British term referring to any sound reproducing machine using disc records, as disc records
were popularized in the UK by the Gramophone Company.
Grammy Shorten form of gramophone, name of the Grammy Awards given by The Recording
granulation noise An audible distortion resulting from quantization error.
graphic equalizer A multi-band variable equalizer using front panel mechanical slide controls as the
amplitude adjustable elements. Named for the positions of the sliders "graphing" the resulting frequency
response of the equalizer. Only found on active designs. Center frequency and bandwidth are fixed for
each band.
Grashof, Nusselt and Prandtl numbers Thermodynamics. All are found in the study of natural
convection as occurs, for example, from heat sinks in audio power amplifiers: Grashof (Gr), is the ratio
of buoyant force to viscous force; Nusselt (Nu) is the coefficient of heat transfer; and Prandtl (Pr) is the
ratio of the molecular diffusion coefficients of momentum in terms of heat, i.e., a property of air. And for
those who love a good formula, this is the correlation for natural convection from a flat plate:
Nu = 0.59 (Gr
gray code A sequence of binary values where only one bit is allowed to change between successive
values. Generally "quieter" (producing less audible interference) than straight binary coding for
execution of commands in audio systems.
gray noise See noise color
Green Book Nickname for the Philips and Sony's ECMA-130 standard document that defines the format
for CD-I (compact disc-interactive) discs; available only to licensees. Compare with Red Book and (3 of 5) [10/3/04 12:29:43 AM]
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Yellow Book.
green noise See noise color
groan box Accordion. (Decharne)
ground Electronics. The common reference point for electrical circuits; the return path; the point of zero
grounding, proper See Steve Macatee's Considerations in Grounding and Shielding , RaneNote: Sound
System Interconnection and Tony Waldron and Keith Armstrong, "Bonding Cable Shields at Both Ends
to Reduce Noise," EMC Compliance Journal, May 2002.
ground lift switch 1. Found on the rear of many pro audio products, used to separate (lift) the signal
ground and the chassis ground connection. 2. Common three-pin to two-pin AC plug adapter used to
reduce ground loops. [NOTE: This is unsafe and illegal. DO NOT USE.] For discussion See Steve
Macatee's Considerations in Grounding and Shielding and RaneNote: Sound System Interconnection.
ground loop 1. Electronics. Within a single circuit, or an audio system, the condition resulting from
multiple ground paths of different lengths and impedances producing voltage drops between paths or
units. A voltage difference developed between separate grounding paths due to unequal impedance such
that two "ground points" actually measure distinct and different voltage potentials relative to the power
supply ground reference point. See Steve Macatee's Considerations in Grounding and Shielding and
RaneNote: Sound System Interconnection 2. Aviation. The tendency of a tailwheel aircraft (vs. tricycle
gear) to pivot around its vertical axis during runway ops in the presence of a high crosswind. [Thanks
groups (aka subgroup or submix) A combination of two or more signal channels gathered together and
treated as a set that can be varied in overall level from a single control or set of controls. Mixing consoles
often provide a group function mode, where the level of any group of incoming singles may be adjusted
by a single slide fader, which is designated as the group fader. Likewise in certain signal processing
equipment with splitting and routing capabilities, you will have the ability to group together, or assign,
outputs allowing control of the overall level by a single external controller. See: Rane SRM 66
group delay Same as envelope delay [technically the time interval required for the crest of a group of
waves to travel through a 2-port network -IEEE.] The rate of change of phase shift with respect to
frequency. Mathematically, the first derivative of phase verses frequency. The rate of change is just a
measure of the slope of the phase shift verses linear (not log) frequency plot. If this plot is a straight line,
it is said to have a "constant" (i.e., not changing) phase shift, or a "linear phase" (or "phase linear" European) characteristic. Hence, constant group delay, or linear group delay, describes circuits or (4 of 5) [10/3/04 12:29:43 AM]
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systems exhibiting constant delay for all frequencies, i.e., all frequencies experience the same delay.
Note that pure signal delay causes a phase shift proportional to frequency, and is said to be "linear
phase," or "phase linear." In acoustics, such a system is commonly referred to as a "minimum phase"
system. For a circuit example, see: Bessel crossover. Also see Siegfried Linkwitz's Group delay and
transient response, and RaneNote: Linkwitz-Riley Crossovers up to 8th-Order: An Overview.
GR plug See: connectors: banana plug
GUI (graphical user interface) A generic name for any computer interface that substitutes graphics (like
buttons, arrows, switches, sliders, etc.) for characters; usually operated by a mouse or trackball. First
mass use was Apple's MacintoshTM computers, but is now dominated by Microsoft's WindowsTM
gut scrapper Violinist. (Decharne)
gyrator filters Term used to describe a class of active filters using gyrator networks. Gyrator is the name
given for RC networks that mimic inductors. A gyrator is a form of artificial inductor where an RC filter
synthesizes inductive characteristics. Used to replace real inductors in filter design. See RaneNote:
Constant-Q Graphic Equalizers.
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Haas Effect Also called the precedence effect, describes the human psychoacoustic phenomena of
correctly identifying the direction of a sound source heard in both ears but arriving at different times.
Due to the head's geometry (two ears spaced apart, separated by a barrier) the direct sound from any
source first enters the ear closest to the source, then the ear farthest away. The Haas Effect tells us that
humans localize a sound source based upon the first arriving sound, if the subsequent arrivals are within
25-35 milliseconds. If the later arrivals are longer than this, then two distinct sounds are heard. The Haas
Effect is true even when the second arrival is louder than the first (even by as much as 10 dB.). In
essence we do not "hear" the delayed sound. This is the hearing example of human sensory inhibition
that applies to all our senses. Sensory inhibition describes the phenomena where the response to a first
stimulus causes the response to a second stimulus to be inhibited, i.e., sound first entering one ear cause
us to "not hear" the delayed sound entering into the other ear (within the 35 milliseconds time window).
Sound arriving at both ears simultaneously is heard as coming from straight ahead, or behind, or within
the head. The Haas Effect describes how full stereophonic reproduction from only two loudspeakers is
possible. (After Helmut Haas's doctorate dissertation presented to the University of Gottingen, Gottingen,
Germany as "Über den Einfluss eines Einfachechos auf die Hörsamkeit von Sprache;" translated into
English by Dr. Ing. K.P.R. Ehrenberg, Building Research Station, Watford, Herts., England Library
Communication no. 363, December, 1949; reproduced in the United States as "The Influence of a Single
Echo on the Audibility of Speech," J. Audio Eng. Soc., Vol. 20 (Mar. 1972), pp. 145-159.)
Hafler, David (1919-2003) American engineer, inventor and member of the Audio Hall of Fame,
considered one of the fathers of high fidelity. He founded Acrosound (1950), Dynaco (1954) and the
David Hafler Company (1972).
half-duplex Pertaining to a transmission over a circuit capable of transmitting in either direction, but
only one direction at a time. See also: duplex
half-wave rectification Term used to describe a rectifier that passes only one-half of each incoming
sinusoid, and does not pass the opposite half-cycle. (IEEE)
Hall effect or Hall voltage In a semiconductor, the Hall voltage is generated by the effect of an external
magnetic field acting perpendicularly to the direction of the current.
Hall, Edwin Herbert (1855-1938) American physicist best known for his 1879 discovery of the Hall
effect. (1 of 9) [10/3/04 12:29:50 AM]
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Hamster switch DJ Mixers. A control found on professional DJ performance mixers that reverses fader
action. For example, if a fader normally is off at the bottom of its travel and on at the top of its travel,
then activating the hamster switch reverses this, so off is now at the top and on is at the bottom of travel,
or alternatively, it swaps left for right in horizontally mounted faders. Used to create the most
comfortable (and fastest) fader access when using either turntable, and to accommodate left-handed and
right-handed performers. Credited to, and named after, one of the original scratch-style crews named The
BulletProof Scratch Hamsters.
handshaking The initial exchange between two communications systems prior to and during
transmission to ensure proper data transfer.
happiness "An agreeable sensation arising from contemplating the misery of another." -- Ambrose
hard clipping See: clipping
hard disk A sealed mass storage unit used for storing large amounts of digital data.
hard disk recording See: DAW (digital audio workstation) and HDR
hardware The physical (mechanical, and electrical) devices that form a system.
hardware key See dongle
harmonic 1. Any of a series of musical tones whose frequencies are integral multiples of the frequency
of a fundamental tone. 2. A tone produced on a stringed instrument by lightly touching an open or
stopped vibrating string at a given fraction of its length so that both segments vibrate. Also called
overtone, partial, partial tone. (AHD)
harmonic distortion See THD
harmonicity The degree to which a sound's timbre conforms to a harmonic series (Thanks to Scott
Wilkinson for this succinct definition).
harmonic series 1. Mathematics. A series whose terms are in harmonic progression, such as 1 + 1/2 +
1/3 + 1/4 + 1/5 + .... 2. Music. A series of tones consisting of a fundamental tone and the overtones
produced by it, and whose frequencies are consecutive integral multiples of the frequency of the
fundamental. (AHD) (2 of 9) [10/3/04 12:29:50 AM]
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harmonic telegraph The original name given by Alexander Graham Bell to his idea that the telegraph
could be used to transmit sound.
HATS (head and torso simulator) Acoustics. A dummy head, with artificial ears and ear canals fitted
with microphones, and a torso, used to measure acoustic parameters.
HAVi (Home Audio/Video interoperability) An industry standard for home networks designed to link
consumer electronics products. Developed by eight consumer giants -- Grundig, Hitachi, Panasonic,
Philips, Sharp, Sony, Thomson Multimedia and Toshiba -- the main aim of this protocol is to ride on
IEEE 1394 interface, connecting digital TVs, set-top boxes, DVD players and other digital consumer
hdCD (high density compact disc) See: DVD
HDCD (high definition compatible digital) Pacific Microsonics' (now owned by Microsoft) trademark
for their encode/decode scheme that allows up to 24 bit, 176.4 kHz digital audio mastering process, yet is
compatible with normal 16 bit, 44.1 kHz CD and DAT formats. Claimed to sound superior even when
not decoded, and to be indistinguishable from the original if decoded.
HDD (high-capacity hard disk drive) See: HDR below.
HDR (hard-disk recorder) An audio recording device based on computer hard disk memory technology.
Typically, these machines are configured like analog tape recorders offering 24-48 tracks, utilizing 24-bit
/ 48-96 kHz data converters with optional I/O to interface with ADAT, TDIF, or AES3, and file format
interchangeability with DAWs.
HDTV (high definition television) The standard for digital television in North America, still being
revised. When finished will include a definition for picture quality at least that of a movie theater, or 35
mm slide, i.e., at least two million pixels (compared to 336,000 pixels for NTSC).
headphones An electromagnetic transducer usually based on the principle of electromagnetic induction
used to convert the electrical energy output of a headphone amplifier into acoustic energy. Popular
nickname is "cans."
headphone sensitivity See sensitivity
headroom A term related to dynamic range, used to express in dB, the level between the typical
operating level and the maximum operating level (onset of clipping). For example, a nominal +4 dBu
system that clips at +20 dBu has 16 dB of headroom. Because it is a pure ratio, there are no units or
reference-level associated with headroom -- just "dB." Therefore (and a point of confusion for many) (3 of 9) [10/3/04 12:29:50 AM]
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headroom expressed in dB accurately refers to both voltage and power. Which means our example has
16 dB of voltage headroom, as well as 16 dB of power headroom. It's not obvious, but it's true. (The
math is left to the reader.)
HeadWize A non-profit (i.e., no ads) site specializing in headphones and headphone listening, featuring
articles, essays, projects and technical papers on all things headphone -- very informative.
H.E.A.R. (Hearing Education and Awareness for Rockers) A non-profit volunteer organization
dedicated to raising awareness of the real dangers of repeated exposure to excessive noise levels from
music which can lead to permanent, and sometimes debilitating, hearing loss and tinnitus.
hearing Perceiving sound by the ear.
heavy-metal Music. A form of rock music characterized by extreme volume, high-intensity electric
guitar, flashy costumes and dramatic stage performances. Originally coined by William Burroughs in his
book, Naked Lunch, it was first voiced in music, "heavy-metal thunder," in Steppenwolf's "Born to be
Wild." The song believed to be the first heavy-metal piece was a remake of Eddie Cochran's
"Summertime Blues" recorded by Blue Cheer in 1968. [McCleary]
HEI (House Ear Institute) Established in 1946, a private nonprofit organization, with an international
reputation as a leader in its field through its applied otologic research and education programs.
Heisenberg, Werner Karl (1901-1976) German physicist and a founder of quantum mechanics. He won
a 1932 Nobel Prize for his uncertainty principle.
Heisenberg uncertainty principle "The more precisely the position is determined, the less precisely the
momentum is known in this instant, and vice versa."
--Heisenberg, uncertainty paper, 1927.
Helmholtz Equation Used in acoustics and electromagnetic studies. It arises, for example, in the
analysis of vibrating membranes, such as the head of a drum, or in solving for room modes. (After
Hermann Ludwig Ferdinand von Helmholtz below.)
Helmholtz, Hermann Ludwig Ferdinand von (1821-1894) German physicist and physiologist who
formulated the mathematical law of the conservation of energy (1847) and invented an ophthalmoscope
(1851) (AHD) [An instrument for examining the interior structures of the eye, especially the retina,
consisting essentially of a mirror that reflects light into the eye and a central hole through which the eye
is examined. You aren't a real doctor without one.] Famous for his book, On the Sensations of Tone first
published in 1862. (4 of 9) [10/3/04 12:29:50 AM]
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Helmholtz resonator When you blow air across the top of an empty bottle to make a sound, you are
demonstrating the principal of a Helmholtz resonator. Click the link to read the details and do the math.
hertz Abbr. Hz. A unit of frequency equal to one cycle per second. [After Heinrich Rudolf Hertz.]
Hertz, Heinrich Rudolf (1857-1894) German physicist who was the first to produce radio waves
artificially. (AHD)
hexadecimal A number system using the base-16, i.e., each number can be any of 16 values. Normally
represented by the digits 0-9, plus the alpha characters A-F. A four-bit binary number can represent each
hexadecimal digit.
Heyerdahl, Thor (1914-2002) Norwegian anthropologist and explorer made famous by his book KonTiki about his epic 1947 expedition voyage to Polynesia.
On a visit to London, Heyerdahl had a busy schedule of appointments. Shortly after
recording a program for the Independent Television Network, he was due at the BBC
studios for an interview. Having been assured by the BBC that a taxi would be sent to pick
him up from the ITN studios, Heyerdahl waited expectantly in the lobby. As the minutes
ticked by, however, he began to grow anxious. He approached a little man in a flat cap,
who looked as if he might be a taxi driver and was obviously searching for someone. "I'm
Thor Heyerdahl," said the anthropologist, "Are you looking for me?" "No, mate," replied
the driver. "I've been sent to pick up four Airedales for the BBC." [Bartlett's Book of
Hi8 See: DA-88
hide A set of drums. (Decharne)
high-cut filter See low-pass filter [In audio electronics, we define things like this just to make sure
you're paying attention.] Contrast with high-pass filter below.
high-pass filter A filter having a passband extending from some finite cutoff frequency (not zero) up to
infinite frequency. An infrasonicfilter is a high-pass filter. Also known as a low-cut filter.
hiss Random high frequency noise with a sibilant quality, most often associated with tape recordings.
hoaxes, audio See Bob Pease's wonderful "What's All This Hoax Stuff, Anyhow?"
Holophonics An acoustical recording and broadcast technology claimed to be the aural equivalent to (5 of 9) [10/3/04 12:29:50 AM]
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holography, hence the name. Holophonics is an encode process that occurs during the recording session
using a special listening device named "Ringo." It is claimed that "playback or broadcast is possible over
headphones or any existing mono or stereo speaker system, with various levels of spatial effect. Optimal
effects occurs when two tracks (stereo) are played utilizing digital technology over headphones and
minimal effect when played over a single mono speaker (two tracks merged into one and played over a
single speaker)."
HomeRF Lite See ZigBee
homicide "The slaying of one human being by another. There are four kinds of homicide: felonious,
excusable, justifiable and praiseworthy, but it makes no great difference to the person slain whether he
fell by one kind or another -- the classification is for advantage of the lawyers." -- Ambrose Bierce.
homophone Words, such as taper and tapir, or timbre and tambour, that are pronounced the same but
differ in meaning, origin, and sometimes spelling. [AHD]
hope "Desire and expectation rolled into one." -- Ambrose Bierce.
hornLoudspeakers. A sound radiator cone mounted onto a loudspeaker diaphragm to amplify its output
based on the same principal found in musical instrument horns..
Horner, William George (1786-1837) English mathematician and inventor of the Zoetrope.
house curve Sound Reinforcement. The name given to the weighting, or alteration, of the sound
equalization for a room. It is a rule-of-thumb for what to do after achieving the flattest possible response.
Different venues require different house curves with wide variation between many favorites. The most
common one is for speech reinforcement in large auditoriums (only) and measures 10 dB down at 10 kHz
with respect to 1 kHz (this is a 3 dB/octave slope). This contrasts to the 2 -3 dB used in many small
control rooms. The proper choice is heavily dependent on the source material (speech vs. music) and the
venue (large vs small; reverberent or dry); there is no one standard.
House Ear Institute See: HEI
house mixer See: FOH
howlround What the British call acoustic feedback.
HR Radio Formerly called IBOC, the digital radio technology that allows simultaneous broadcasting of
analog and digital signals using present radio spectrum allocations. (6 of 9) [10/3/04 12:29:50 AM]
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HRRC (Home Recording Rights Coalition) An advocacy group that includes consumers, retailers,
manufacturers and professional servicers of consumer electronics recording products.
HRTF (head-related transfer function) The impulse response from a sound source to the eardrum is
called the head-related impulse response (HRIR), and its Fourier transform is called the head-related
transfer function (HRTF). The HRTF captures all of the physical cues to source localization, and is a
surprisingly complicated function of four variables: three space coordinates (azimuth, elevation & range)
and frequency, and to make matters worst, they change from person to person. Interaural (i.e., between
the ears) time differences, interaural time delays and the physical effects of diffraction of sound waves
by the torso, shoulders, head and pinnae modify the spectrum of the sound that reaches the eardrums.
These changes allow us to localize sound images in 3D space and are captured by the HRTFs. HRTFs
have been named and studied since at least the early '70s (Blauert)
HTML (hypertext markup language) The software language used on the Internet's World Wide Web
(WWW). Used primarily to create home pages containing hypertext.
HTTP (hypertext transfer protocol) The name for the protocol that moves documents around the
Internet/Web. Used by the various servers and browsers to communicate over the net.
hub 1. In broadband LAN use, a central location of a network that connects network nodes through
spokes, usually in a star architecture. Think of it as a digital splitter, or distribution amplifier. 2. In
complex systems, hubs perform the basic functions of restoring signal amplitude and timing, collision
detection and notification, and signal broadcast to lower-level hubs.
hubbub Loud, confused, or disagreeable sound or sounds that emphasizes turbulent activity and
concomitant din. [AHD]
Huffman coding or Huffman algorithm One of the MP3 and AAC techniques used in digital audio data
compression. While not a compression technique in itself, it is used in the final steps to code the process,
and is an ideal complement of the perceptual coding. Huffman codes are used in nearly every application
that involves the compression and transmission of digital data, such as fax machines, modems, computer
networks, and high-definition television. For more details, see: Huffman Coding [After David Huffman
hullabaloo Great noise or excitement; uproar; disorderly tumult together with loud, bewildering sound.
hum components The harmonics of the AC mains supply. The Americas (except the southern half of
South America), Japan, Taiwan, Korea and the Philippines use a 60-Hz system, placing the most
annoying 2nd and 3rd harmonics at 120 Hz and 180 Hz. For Europe, and the rest of the world using 50Hz mains, these components fall at 100 Hz and 150 Hz. (7 of 9) [10/3/04 12:29:50 AM]
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hurdy-gurdyMusical Instrument. 1. A medieval stringed instrument played by turning a rosined wheel
with a crank and depressing keys connected to tangents on the strings. 2. Any instrument, such as a barrel
organ, played by turning a crank. [AHD] Hit the link for photos of this strange and wonderful
HVAC Construction. Term used to stand for the heating, ventilating, & air conditioning system of any
building. Electrical engineering. Term used to mean high-voltage alternating current.
hybrid A telecommunication term used to describe an interface box that converts a conversation (or data
signal) coming in on two pairs (one pair for each direction of the conversation or signal) onto one pair
and vice versa (i.e., a 2-wire to 4-wire converter). This is necessary because all long distance circuits are
two pairs, while most local circuits are one pair. The name comes from the original use of a "hybrid coil"
in the telephone whose function was to keep the send and receive signals separated. Both analog and
digital hybrid designs are found. A fundamental (and unavoidable) problem in any 2-wire to 4-wire
design is leakage (crosstalk) between the transmit and receive signals. In analog designs leakage is
reduced by modeling the impedance seen by the transmit amplifier as it drives the hybrid coil. Because
telephone-line impedance is complex and not well modeled by a simple passive RLC circuit, only 10 dB
to 15 dB of leakage reduction is usually possible. Digital hybrids use DSP technology to model and
dynamically adapt to provide much greater reduction than analog designs, typically resulting in
reductions of 30 dB to 40 dB. However, the best digital hybrids incorporate acoustic echo cancelling
(AEC) circuitry to gain even greater improvements. The AEC works to cancel out any remaining signal
coming from the loudspeaker (far-end received signal) from the microphone signal before they can be
retransmitted to the far end as acoustic echo. Digital hybrids with AEC achieve total leakage reduction of
50 dB to 65 dB.
hypercardiod microphone See: cardiod microphone.
hyperlink The protocol that allows connecting two Internet resources via a single word or phrase;
allowing the user a simple point-and-click method to create the link.
HyperPhysics A website concept created by Carl R. (Rod) Nave, Department of Physics and
Astronomy, Georgia State University. "An exploration environment for concepts in physics which
employs concept maps and other linking strategies to facilitate smooth navigation." [An incredible site.
You can get lost here for hours. I can't recommend it enough.]
hypersonic sound Term that describes the emerging audio technology of using wireless ultrasonic
signals and nonlinear signal mixing techniques to produce sound located only in very specific areas. First
discovered and described by Helmholtz in the late 1800s, it is now finding use in ATMs, dynamic
signage and museum exhibits. American Technology Corp. is leading the pack with their HSS®
HyperSonic Sound products. (8 of 9) [10/3/04 12:29:50 AM]
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hypertext Within WWW documents, the linking of words to other sections of text, pictures or sound is
called hypertext. Hypertext is created using the HTML software language. Also used frequently in Help
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IACC (interaural cross-correlation coefficient) A measure of the difference in arrival times between the
ears of a listener. It is expressed in values ranging from -1 (arriving signals equal in magnitude but
exactly out of phase) to 0 (arriving signals have no similarity) to +1 (identical arriving signals, i.e. same
amplitude & phase).
IBOC (in-band on-channel) Original name for the digital radio technology that allows simultaneous
analog and digital broadcasting using existing band allocations. See HR Radio for new name and details.
IC (integrated circuit) A solid-state device with miniaturized discrete active components on a single
semiconductor material.
ID3 tag (Identification 3 tag) Adds a small chunk of extra data ("tag") to the end of an MP3 file to carry
information about the audio and not just the audio itself. Developed by Eric Kemp in 1996.
IEC (International Electrotechnical Commission) A European organization (headquartered in Geneva,
Switzerland) involved in international standardization within the electrical and electronics fields. The
U.S. National Committee for the IEC operates within ANSI.
IECEE (IEC System for Conformity Testing and Certification of Electrical Equipment)
IEEE (Institute of Electrical and Electronic Engineers) The largest professional organization for
electrical engineers. Primarily concerned with education and standardization.
IEEE-488 also referred to as the general purpose interface bus (GPIB). Most common parallel format
computer interface for simultaneous control of up to 15 multiple peripherals.
IEEE 754-1985 Standard for binary floating-point arithmetic often referred to as IEEE 32-bit floatingpoint. A standard that specifies data format for floating-point arithmetic on binary computers. It divides a
32-bit data word into a 24-bit mantissa and an 8-bit exponent.
IEEE 802.3af See: PoE
IEEE-1394 (aka Firewire) A joint Apple and TI implementation of the IEEE P1394 Serial Bus Standard. (1 of 9) [10/3/04 12:29:59 AM]
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It is a high-speed (100/200/400 Mbits/sec now, with 1 Gbit/s on the horizon) serial bus for peripheral
devices. Supported by Apple, IBM, Intel, Microsoft and Sony, it is intended to replace Apple Desktop
Bus (ADB) and SCSI (Microsoft announced Windows support for IEEE 1394). Firewire supports
automatic configuration ("plug and play") and hot-plugging (changing peripheral devices while running).
It is also isochronous, meaning that a fixed slice of bandwidth can be dedicated to a particular peripheral video, for instance. IEEE 1394 aims to become the optimal digital interface for 21st-century applications.
Fast, inexpensive and reliable for audio/video as well as computer peripherals, IEEE 1394 carries all
forms of digitized video and audio. A single Firewire interface can be used for all entertainment-center
interconnections, done in a daisy-chain fashion. New computer peripherals such as digital television, CDROM, DVD, digital cameras (Sony was first) and home networks are the first users. See: USB for
complementary low-speed system.
IEM (in-ear monitors) A special earpiece or earplug containing high quality miniature loudspeaker
systems, similar to hearing aids, used for on-stage and recording studio purposes in lieu of traditional
floor foldback monitors.
IEV (International Electrotechnical Vocabulary) A valuable database, made available on-line by the
IEC. It contains over 18,500 electrotechnical concepts divided into 73 subject areas (IEV parts). Each
concept contains equivalent terms in English, French and German.
IFB (interrupted foldback) (aka talent cueing) An audio sub-system allowing on-air personnel ("talent")
to receive via headphones, or ear monitors, the normal program audio mixed with audio cues from the
production director, or their assistants.
IFPI (International Federation of Phonographic Industry) The organization representing the
international recording industry. It comprises a membership of 1500 record producers and distributors in
76 countries.
IGBT (insulated-gate bipolar transistor) A hybrid form of a MOSFET and bipolar transistor producing
an electrically insulated gate instead of a base connection combined with a robust bipolar output. It
combines MOS gate control with bipolar current control.
IGFET (insulated-gate field-effect transistor) Formal name for MOSFET or an FET with one or more
gate electrodes electrically insulated from the channel. [IEEE]
IGTP (isolated ground technical power) Audio/Video Electrical Power Systems.
IHF (Institute of High Fidelity) The old organization of North American hi-fi manufacturers that created
voluntary industry standards for testing and specifying consumer electronics. The IHF merged with the
EIA in 1979. The IHF worked closely with the IRE. Today the AES is responsible for setting audio
standards for the United States. (2 of 9) [10/3/04 12:29:59 AM]
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IIR (infinite impulse-response) filter A commonly used type of digital filter. This recursive structure
accepts as inputs digitized samples of the audio signal, and then each output point is computed on the
basis of a weighted sum of past output (feedback) terms, as well as past input values. An IIR filter is
more efficient than its FIR counterpart, but poses more challenging design issues. Its strength is in not
requiring as much DSP power as FIR, while its weakness is not having linear group delay and possible
ILD (interaural level difference) See: interaural.
IM or IMD (intermodulation distortion) An audio measurement designed to quantify the distortion
products produced by nonlinearities in the unit under test that cause complex waves to produce beat
frequencies, i.e., sum and difference products not harmonically related to the fundamentals. For example,
two frequencies, f1 and f2 produce new frequencies f3 = f1 - f2; f4 = f1 + f2; f5 = f1 - 2f1; f6 = f1 + 2f2,
and so on. See RaneNote: Audio Specifications
Numerous tests exist, each designed to "stress" the unit under test differently. The most popular follow:
SMPTE/DIN IMD The most common IMD measurement. SMPTE standard RP120-1994
and DIN standard 45403 are similar. Both specify a two-sine wave test signal consisting of
a large amplitude low-frequency tone linearly mixed with a high-frequency tone at ¼ the
amplitude of the low frequency tone. SMPTE specifies 60 Hz and 7 kHz mixed 4:1. The
DIN specification allows several choices in both frequencies, with 250 Hz and 8 kHz being
the most common.
ITU-R (old CCIF), Twin-Tone, or Difference-Tone IMD All these terms refer to the
same test and are used interchangeably. The test specifies two equal-amplitude closely
spaced high frequency signals. Common test tones are 19 kHz and 20 kHz for full audio
bandwidth units. While all combinations of IM distortion products are possible, this test
usually measures only the low-frequency second-order product falling at f2-f1, i.e., at 1
DIM/TIM (dynamic/transient intermodulation distortion) A procedure designed to test
the dynamic or transient behavior, primarily, of audio power amplifiers. The other IM tests
use steady-state sine wave tones, which do not necessarily reveal problems caused by
transient operation. In particular, audio power amplifiers with high amounts of negative
feedback were suspect due to the inherent time delay of negative feedback loops. The
speculation was that when a rapidly-changing signal was fed to such an amplifier, a finite
time was required for the correction signal to travel back through the feedback loop to the
input stage and that the amplifier could be distorting seriously during this time. The most
popular test technique consists of a large amplitude 3 kHz square wave (band-limited to
~20 kHz) [Historical Note: This test proved that as long as the amplifier did not slew-limit
for any audio signal, then the loop time delay was insignificant compared to the relatively
long audio periods. Thus, properly designed negative feedback was proved not a problem.
Subsequently, this test has fallen into disuse.] (3 of 9) [10/3/04 12:29:59 AM]
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IMA (International MIDI Association) The original association that developed MIDI, now defunct and
replaced by the MMA.
image impedances The impedances that will simultaneously terminate all of a network's inputs and
outputs in such a way that at each of its inputs and outputs the impedances in both directions are equal. In
this manner the input and output impedances "see" their own "image." (IEEE)
image parameters Fundamental network functions, namely image impedances and image transfer
functions, used to design or describe a filter. (IEEE)
imaginary number A number whose square equals minus one, or, alternatively, a number that represents
the square root of minus one. See Nahin'sAn Imaginary Tale for its incredible history.
impedance A measure of the complex resistive and reactive attributes of a component in an alternatingcurrent (AC) circuit. Impedance is what restricts current flow in an AC electrical circuit; impedance is not
relevant to DC circuits. In DC circuits, resistors limit current flow (because of their resistance). In AC
circuits, inductors and capacitors similarly limit the AC current flow, but this is now because of their
inductive or capacitive reactance. Impedance is like resistance but it is more. Impedance is the sum of a
circuit, or device's resistance AND reactance. Reactance is measured in ohms (like resistance and
impedance) but is frequency-dependent. Think of impedance as the complete or total current limiting
ohms of the circuit -- the whole banana. Since AC circuits involve phase shift -- i.e., the voltage and
current are rarely in phase due to the storage effects (think time; it takes time to charge and discharge) of
capacitors and inductors, the reactance is termed "complex," that is there is a "real" part (resistive) and an
"imaginary" part (bad terminology, but it means the phase shifting resistance part). To summarize:
resistance has no phase shift; reactance (capacitors & inductors in AC circuits) includes phase shift; and
impedance, is the sum of resistance and reactance. Just that simple.
impedance matching Making the output driving impedance and the next stage input impedance equal,
often requiring the insertion of a special impedance matching network. For why impedance matching is
not necessary (and, in fact, hurtful) in pro audio applications, see William B. Snow, "Impedance -Matched or Optimum," [written in 1957!] Sound Reinforcement: An Anthology, edited by David L.
Klepper (Audio Engineering Society, NY, 1978, pp. G-9 - G-13), and RaneNote: Unity Gain and
Impedance Matching: Strange Bedfellows.
impulse response Acoustic measurements. A theoretical impulse has an amplitude vs. time response that
is infinitely high and infinitely narrow -- a spike with zero duration and infinite amplitude, but finite
energy. This means the energy is spread over a very large frequency range, making impulses an ideal
source for acoustic measurements. Real world use of the mathematical impulse consists of a test impulse
that has a very short time duration and whose amplitude is limited to whatever will not overload the
system components. The Fourier theorem tells us that this rectangular pulse is nothing more than a sum (4 of 9) [10/3/04 12:29:59 AM]
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of sine and cosine functions with known amplitudes and phases, therefore the impulse response of a
linear system occurs in the time domain, but also contains all of the frequency information. By capturing
the system impulse response with a digital storage scope and then performing a Fast Fourier Transform
(FFT) analysis, the frequency-domain response (amplitude and phase) is obtained. [Very powerful tool.]
inductance A force that resists the sudden buildup of electric current (as opposed to capacitance which
resists the sudden buildup of electric voltage). [IEEE]
inductive reactance See impedance
inductor Circuit symbol: L. A device consisting of one or more windings, with or without a magnetic
core, for introducing inductance into an electric circuit. [IEEE]
infrasonic Generating or using waves or vibrations with frequencies below that of audible sound.
Compare with subsonic - commonly used (erroneously) to mean infrasonic.
infrasonic filter (aka rumble filter) A high-pass filter used with phonograph turntables to reduce the
effects of low frequency noise and vibration, called rumble, caused by imperfections in turntable
performance and warped records. Often mistakenly called subsonic filter. Since typical rumble
frequencies occur in the 3-10 Hz area, most infrasonic filters have a corner frequency of around 15 Hz,
with a steep slope, or rolloff rate, of 18 dB/octave, and a Butterworth response.
initial time-delay gap See ITDG.
initialism An abbreviation consisting of the first letter or letters of words in a phrase (for example, IRS
for Internal Revenue Service), syllables or components of a word (TNT for trinitrotouluene), or a
combination of words and syllables (ESP for extrasensory perception) and pronounced by spelling out the
letters one by one rather than as a solid word. Compare with acronym.
inline mixer Term referring to the normal long narrow vertical strip format common to all medium to
large-scale mixing console designs (mixers). Non-inline designs typically refer to rack-mount mixers, i.e.,
those that are 19" wide, and designed to fit into standard rack cases. These are as small as 1U space
(1.75" H). Sometimes these are designed similar to an inline design laying on its side, now having a
horizontal control flow instead of a vertical one. In the middle of the pack are rack-mount mixers that still
use the inline vertical format, but do rack mount, but normally take up 10 or more spaces.
in-phase In a synchronized or correlated way. See polarity and phase et al.
input referred noise See EIN (5 of 9) [10/3/04 12:29:59 AM]
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insertion loss The loss of voltage (or power), as measured in dB, resulting from placing a pad (or other
power absorbing network) between a voltage (or power) source and its load impedance. It is the ratio of
the voltage (or power) absorbed in the load without the pad (or network) to that when the network is
inserted. For example if the voltage across a load is 2 volts without a network and 1 volt with the
network, then the insertion loss is stated as 6 dB.
insert loop The preferred term for a specialized I/O point found on mixers utilizing a single 1/4" TRS
jack following the convention of tip = send, ring = return, & sleeve = signal ground. Used to patch in an
outboard processor using only one cable, with unbalanced wiring. A stereo insert loop requires two jacks.
Compare with effects loop.
in situ In the original position. [AHD]
instrument-level See levels.
intelligibility See: speech intelligibility.
interaural Hearing. Literally "between the ears," it is the comparison of sound heard by one ear verses
the same sound heard by the other ear.
Specific terms include interaural time difference (ITD) (different arrival times due to the distance
between the ears) and interaural level difference (ILD) (different arrival intensities due to the
diffraction or shadowing caused by the head as an obstacle).
interference Acoustics. Anything that hinders, obstructs, or impedes sound travel, including another
sound wave. See link.
intermodulation distortion See IMD
interlayer-transfer See: print-through
interleaving The process of rearranging data in time. Upon de-interleaving, errors in consecutive bits or
words are distributed to a wider area to guard against consecutive errors in the storage media.
International Music Products Association See NAMM
International System of Units See SI
Internet To try and define the Internet in a few words is a futile task. Click the hyperlink for a wonderful
Internet history timeline. Contrast with WWW. (6 of 9) [10/3/04 12:29:59 AM]
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interpolating response Term adopted by Rane Corporation to describe the summing response of
adjacent bands of variable equalizers using buffered summing stages. If two adjacent bands, when
summed together, produce a smooth response without a dip in the center, they are said to interpolate
between the fixed center frequencies, or combine well. [Historical note: Altec-Lansing first described
their buffered equalizer designs as combining and the terminology became commonplace. Describing
how well adjacent bands combine is good terminology. However, some variations of this term confuse
people. The phrase "combining filter" is a misnomer, since what is meant is not a filter at all, but rather
whether adjacent bands are buffered before summing. The other side of this misnomer coin finds the
phrase "non-combining filter." Again, no filter is involved in what is meant. Dropping the word "filter"
helps, but not enough. Referring to an equalizer as "non-combining" is imprecise. All equalizers combine
their filter outputs. The issue is how much ripple results. For these reasons, Rane adopted the term
"interpolating" as an alternative. Interpolating means to insert between two points, which is what
buffering adjacent bands accomplishes. By separating adjacent bands when summing, the midpoints fill
in smoothly without ripple.] See RaneNote: Constant-Q Graphic Equalizers and RaneNote: Exposing
Equalizer Mythology
interrupted foldback See IFB
intimacy See ITDG.
inverse square law Sound Pressure Level. Sound propagates in all directions to form a spherical field,
thus sound energy is inversely proportional to the square of the distance, i.e., doubling the distance
quarters the sound energy (the inverse square law), so SPL is attenuated 6 dB for each doubling.
I/O (input/output) Equipment, data, or connectors used to communicate from a circuit or system to other
circuits or systems, or the outside world.
IP (intellectual property) Referring to protected proprietary information, usually in the form of a patent,
maskworks (integrated circuits or printed circuit boards), a copyright, a trade secret, or a trademark.
Often misused to mean many different things.
IP (internet protocol) IP is the most important of the protocols on which the Internet is based. Originally
developed by the Department of Defense to support interworking of dissimilar computers across a
network, IP is a standard describing software that keeps track of the Internet work addresses for different
nodes, routes outgoing messages, and recognizes incoming messages. It was first standardized in 1981.
This protocol works in conjunction with TCP and is identified as TCP/IP.
IP address Another name for an Internet address. A 32-bit identifier for a specific TCP/IP host computer
on a network, written in dotted decimal form, such as, with each of the four fields
assigned 255 values, organized into hierarchical classes. Whenever you click on a name address like, this creates a path to the domain naming system (DNS) that translates the name (7 of 9) [10/3/04 12:29:59 AM]
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into the IP address, which is used to connect.
IRE ( Institute of Radio Engineering ) Now defunct, the organization merged with IEEE. Also see: IHF.
IRMA (International Recording Media Association) An advocacy group for the growth and
development of all recording media and is the industry forum for the exchange of information regarding
global trends and innovations.
iron vane Electrical meter mechanism. Rugged design and construction, used primarily in AC voltage,
current and power measurements. It features an accurate true rms measurement capability when
measuring distorted or non-sinusoidal waveforms.
ISBN (International Standard Book Number) In bibliography, a 10-digit number assigned to a book
which identifies the work's national, geographic, language, or other convenient group, and its publisher,
title, edition and volume number. Its numbers are assigned by publishers and administered by designated
national standard book numbering agencies, such as R.R. Bowker Co. in the U.S., Standard Book
Numbering Agency Ltd. in the U.K., Staatsbibliothek Preussischer Kulterbesitz (Prussian State Library)
in Germany, and the Research Library on African Affairs in Ghana. Each ISBN is identical with the
Standard Book Number, originally devised in the U.K. , with the addition of a preceding national group
identifier. [Now if that isn't more than you will ever need to know about this subject then I'll eat a book.]
ISDN (Integrated Services Digital Network) A high-capacity digital telecommunication network (mainly
fiber optic) based on an international telephone standard for digital transmission of audio, data and
signaling - all in addition to standard voice telephone calls. A cost-effective alternative to satellite links.
ISO (International Standards Organization or International Organization for Standardization)
Founded in 1947 and consisting of members from over 90 countries, the ISO promotes the development
of international standards and related activities to facilitate the exchange of goods and services
worldwide. The U.S. member body is ANSI. [Interesting tidbit: according to ISO internet info, "ISO" is
not an acronym. It is a derived Greek word, from isos, equal. For example, isobar, equal pressure, or
isometric, equal length. Take a small jump from "equal" to "standard" and you have the name of the
organization. It offers the further advantage of being valid in all the official languages of the organization
(English, French & Russian), whereas if it were to be an acronym it would not work for French and
isolation Acoustics. The isolation of sound is the process by which sound energy is contained or blocked
as opposed to being converted into heat (see: absorption). For a good discussion of the differences read
the excellent short article by Kurt Graffy, "More Or Less: The Difference Between Absorption And
Isolation," System Contractor News, April 2003, p. 96, who also provides this wonderful quote attributed
to Ted Schultz of Bolt, Beranek and Newman: "Mistaking sound absorption for sound isolation is like
mistaking a diaper for an umbrella." [... that clears up all confusion now doesn't it?] (8 of 9) [10/3/04 12:29:59 AM]
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isochronous (pronounced "i-sok-ronus") ("iso" equal + "chronous" time) A term meaning time sensitive;
isochronous transmission is time sensitive transmission. For example, voice and video require
isochronous transmission since audio/video synchronization is mandated.
ISRC (International Standard Recording Code) The international identification system for sound
recordings and music video recordings.
ISWC (International Standard Musical Work Code) A unique, permanent and internationally
recognized reference number for the identification of musical works per International Standard ISO
ITD (interaural time difference) See: interaural.
ITDG (initial time-delay gap) Acoustics. The difference in time between the first arrival of direct sound
and the first arrival of reflected sound at the listener. The sensation of intimacy is quantitatively measured
by the ITDG. First defined in 1962 by Beranek in Music, Acoustics & Architecture.
ITU (International Telecommunications Union) Headquartered in Geneva, Switzerland, ITU is an
international organization within which governments and the private sector coordinate global
telecommunication networks and services. The ITU is divided into three sectors: radiocommunications
(ITU-R), telecommunications development (ITU-D), and telecommunications standards (ITU-T).
ITVA (International Television Association) A global community of professionals devoted to the
business and art of visual communication.
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jacket Wire & Cable. The insulating layer of material that surrounds a wire or cable offering protection;
also called sheath..
jackfield British term for patchbay
jacks and plugs Common name for audio connectors, where jack = female and plug = male is the
standard convention for 1/4" and RCA -- only -- not followed for other types of connectors. If a
connector is on the end of a cable -- XLR and others -- then either sex is a plug. [Hey, don't yell at me, I
don't make the rules, I just report them.]
JADE (Joint Audio Decoder Encoder) Siemens trademark for their device that implements voice
compression algorithms.
jam sync 1. The process of regenerating SMPTE timecode from an original source. Used for repair as
well as for new copies. 2. A recording studio in Nashville specializing in multichannel and multimedia
run by KK Proffitt and Joel Silverman.
jass Jazz music, written both ways from 1913 up until around 1920, when the word "jazz" became the
accepted spelling. (Decharne)
Jawaiian Music. A reggae genre combining traditional Hawaiian and Jamaican styles. Compare with
JavaTM The trademarked name for a powerful object-oriented programming language developed by Sun
Microsystems. Java allows high-speed fully interactive Web pages to be developed for the Internet or any
type of platform.
jazz A style of music, native to America, characterized by a strong but flexible rhythmic understructure
with solo and ensemble improvisations on basic tunes and chord patterns and, more recently, a highly
sophisticated harmonic idiom. (AHD) See jass.
jerk Mathematics. The (first) derivative of acceleration, i.e., it is a measure of the rate of change of (1 of 3) [10/3/04 12:30:05 AM]
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acceleration -- just as velocity is the derivative of speed, and acceleration is the derivative of velocity.
Elevator makers are among those interested in measuring it, for example Otis Elevator Company has a
transducer that measures jerk by differentiating acceleration. (Thanks to Glenn White for the Otis
JFET (junction field-effect transistor) See FET
jiffy An actual unit of time, representing 1/100th of a second. [See Rowlett's How Many? A Dictionary of
Units of Measurement for the complete details.]
jiggumbob A trinket; a knick-knack; a slight contrivance in machinery. (Lynch)
jitter A tendency towards lack of synchronization caused by electrical changes. Technically the
unexpected (and unwanted) phase shift of digital pulses over a transmission medium. Time skew; a
discrepancy between when a digital edge transition is supposed to occur and when it actually does occur think of it as nervous digital, or maybe a digital analogy to wow and flutter.
jitter timing error Short-term deviations of the transitions of a digital signal from their ideal positions in
Johnson noise or thermal noise A form of white noise resulting from thermal agitation in electronic
components. For example, a simple resistor hooked up to nothing generates noise, and the larger the
resistor value the greater the noise. It is called thermal noise or Johnson noise and results from the
motion of electron charge of the atoms making up the resistor (called thermal agitation, which is caused
by heat - the hotter the resistor, the noisier. [After John Bertrand Johnson (1887-1970), Swedish-born
American physicist who first observed thermal noise while at Bell Labs in 1927, publishing his findings
as "Thermal agitation of electricity in conductors," Phys. Rev., vol. 32, pp. 97-109, 1928.]
joule Abbr. J or j. 1. The International System unit of electrical, mechanical, and thermal energy. 2. a. A
unit of electrical energy equal to the work done when a current of one ampere is passed through a
resistance of one ohm for one second. b. A unit of energy equal to the work done when a force of one
newton acts through a distance of one meter. (AHD)
Joule, James Prescott (1818-1889) British physicist who established the mechanical theory of heat and
discovered the first law of thermodynamics: a form of the law of conservation of energy whose discovery
he shared with Hermann von Helmholtz, Julius von Mayer and Lord Kelvin. (AHD)
JPEG (Joint Photographic Experts Group) A standard for lossy compression of graphic-image files.
juke A roadside drinking establishment that offers inexpensive drinks, food, and music for dancing, (2 of 3) [10/3/04 12:30:05 AM]
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especially to the music of a jukebox. [Derivative Note: probably from Gullah juke, joog disorderly,
wicked of West African origin; Wolof dzug to live wickedly Mandingo (Bambara) dzugu wicked. Gullah,
the English-based Creole language spoken by Black people off the coast of Georgia and South Carolina,
retains a number of words from the West African languages brought over by slaves. One such word is
juke, -- bad, wicked, disorderly, -- the probable source of the English word juke. Used chiefly in the
Southeastern states, juke (also appearing in the compound juke joint) means a roadside drinking
establishment that offers cheap drinks, food, and music for dancing and often doubles as a brothel. "To
juke" is to dance, particularly at a juke joint or to the music of a jukebox whose name, no longer regional
and having lost the connotation of sleaziness, contains the same word. (AHD) ... and you thought you
were smart.
just intonation or just temperment Music. A musical scale employing frequency intervals represented
by the ratios of the smaller integers of the harmonic series. [Olson] Compare: equal temperment
JSA (Japanese Standards Association) The National Standards organization responsible for
coordinating standards preparation in Japan.
justify To shift a numeral so that the most significant digit, or the least significant digit, is placed at a
specific position in a row.
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K2-W Designation for a famous tube-based 'modern' general-purpose operational amplifier built by
Philbrick beginning in 1951.
ka Abbreviation for cathode.
kazoo A toy musical instrument with a membrane that produces a buzzing sound when a player hums or
sings into the mouthpiece. The word origin is believed to come being imitative of its sound. [AHD]
kelvin Abbr. K The International System unit of absolute temperature equal to 1/273.16 of the absolute
temperature of the triple point of water. This unit is equal to one Celsius degree. A temperature in kelvin
may be converted to Celsius by subtracting 273.16. (AHD) [After First Baron Kelvin]
Kelvin, William Thomson, First Baron (1824-1907) British physicist who developed the Kelvin scale
of temperature (1848) and supervised the laying of a transatlantic cable (1866). His pioneering work in
thermodynamics and electricity helped develop the law of the conservation of energy. (AHD)
Kelvin worked out an improved method for measuring the depth of the sea using piano
wire and a narrow-bore glass tube, stoppered at the upper end. While experimenting with
this invention, he was interrupted one day by his colleague James Prescott Joule. Looking
with astonishment at the lengths of piano wire, Joule asked him what he was doing.
"Sounding," said Thompson. "What note?" asked Joule. "The deep C," returned
Thompson. [Bartlett's Book of Anecdotes]
keeper A bar of material (usually soft iron) with very high magnetic permeability placed across the poles
of a permanent magnet (effectively shorting out the magnetic field) to protect it from demagnetization.
Most often seen on horseshoe or U-shaped magnets. [Thanks to Glenn White.]
key Music. 1. The pitch of a voice or other sound. 2. The principal tonality of a work: an etude in the key
of E. 3. A tonal system consisting of seven tones in fixed relationship to a tonic, having a characteristic
key signature and being the structural foundation of the bulk of Western music; tonality. (AHD)
keyable or keying Signal Processors. The ability to start or trigger a process by applying an external
signal, usually to a side-chain. (1 of 4) [10/3/04 12:30:08 AM]
Rane Professional Audio Reference (K)
keynote The tonic of a musical key. (AHD)
Key West audion Nickname given the first use of the audion tube by the Navy at their wireless station in
Key West, Florida.
KHN filter See state-variable filter
kHz (kilohertz) One thousand (1,000) cycles per second.
kibi Symbol Ki New term standardized by the IEC as Amendment 2 to IEC 60027-2 Letter Symbols to be
Used in Electrical Technology to signify binary multiples of 1024 (i.e., 2E10). Meant to distinguish
between exact binary and decimal quantities, i.e., 1024 verses 1000. For example, it is now 16 kibibits,
abbreviated 16 Kib, not 16 kilobits or 16 Kb.
kilo- Abbreviated k (always lower-case). A prefix signifying one thousand (10E3).
Kilo- Abbreviated K (always upper-case). A prefix popularly used in computer work to signify multiples
of 1024 (i.e., 2E10), but should use kibi. Meant to distinguish base-2 (binary) from base-10 (decimal)
magnitudes. For example, a "16 K" memory is actually 16,384 bits (i.e., 16 times 1024, or 2E14), but
should now read "16 Ki".
kilovar A unit equal to one thousand voltamperes.
Kirchoff, Gustav Robert (1824-1887) German physicist noted for his research in spectrum analysis,
optics, and electricity. (AHD)
Kirchoff's Law Electronics. The amount of current flowing into a node exactly equals the amount of
current flowing out of the same node; after Gustav Robert Kirchoff (see above).
Klipsch, Paul W. (1904-2002) American engineer and inventor best know for inventing the
"Klipschorn" below. He was one of the American audio pioneers. Member of the Audio Hall of Fame.
Klipschorn® A type of full-range loudspeaker developed in 1941 with a revolutionary low end (Paul W.
Klipsch, "A Low Frequency Horn of Small Dimensions," JASA, Vol. 13 October 1941; U.S. Pat. Nos.
2,310,243 & 2,373,692). By using the corner of the room as an extension of the folded horn within the
cabinet, it was able to reproduce low-distortion tones down to 30 Hz. The Klipschorn is claimed as the
only speaker in the world that has been in continuous production since the '40s. [After Paul W. Klipsch
above.] (2 of 4) [10/3/04 12:30:08 AM]
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Kloss, Henry (1929-2002) American engineer and inventor, best known for inventing the acousticsuspension loudspeaker and the large-screen projection television; founded four successful consumer
electronics companies: Acoustic Research, KLH, Advent and Cambridge SoundWorks. Member of the
Audio Hall of Fame.
kludge or kluge A system, especially a computer system, that is constituted of poorly matched elements
or of elements originally intended for other applications. (AHD) Or as an article by Jackson Granholme
in "Datamation" put it: "An ill-assorted collection of poorly matching parts, forming a distressing
whole." [From AHD: The word kludge is not "etymologist-friendly," having many possible origins, none
of which can be definitively established. This term, found frequently in the jargon of the engineering and
computer professions, denotes a usually workable but makeshift system, modification, solution, or repair.
Kludge has had a relatively short life (first recorded in 1962 although it is said to have been used as
early as 1944 or 1945) for a word with so many possible origins. The proposed sources of the word,
German klug, kluge, "intelligent, clever," or a blend of klutz and nudge or klutz and refudge, do not
contain all the necessary sounds to give us the word, correctly pronounced at least. The notions that
kludge may have been coined by a computer technician or that it might be the last name of a designer of
graphics hardware seem belied by the possibility that it is older than such origins would allow. It seems
most likely that the word kludge originally was formed during the course of a specific situation in which
such a device was called for. The makers of the word, if still alive, are no doubt unaware that
etymologists need information so they can stop trying to "kludge" an etymology together.]
klystron The name -- from the Greek, as coined by scientists at Stanford University -- was registered by
Sperry Gyroscope Company in the late 1930s for their velocity-modulated, ultra-high-frequency tube. As
described by them in an ad published in a 1945 issue of Scientific American, "it is an apt description of
the bunching of electrons between spaced grids within the tube." In the spirit of voluntary standardization
they gave the name to the public for free use as the designation for velocity-modulated tubes of any
manufacture. [Old klystron tubes make the best TV lamps.]
knee (of a curve) The point on a curve where change begins to occur; a section resembling the human
knee exhibiting bending.
Knudsen, Vernon Oliver (1893-1974) American physicist who studied and worked under Dr. Harvey
Fletcher , helped found the ASA, and was the first dean of the UCLA Physics Department, then vice
chancellor of the university and finally chancellor.
Kodak See: Muzak
kSPS (kilo samples per second) One thousand (1,000) samples per second. A measurement of data
converter speed.
Kundt's tube Named after A.A. Kundt in 1866 who developed this apparatus for measuring the speed of (3 of 4) [10/3/04 12:30:08 AM]
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sound in gases. It allows visualizing acoustic standing waves.
kVA (kilovoltamperes) One thousand (1,000) voltamperes. See voltampere.
KVM (keyboard/video/mouse) Computers. An adapter box that allows multiple computers to share the
same keyboard, monitor and mouse.
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L The electronic symbol for an inductor.
LAB (Live Audio Board) Topics related to sound reinforcement and application of audio for live events -the most active pro audio forum on the Web, created by road dog Dave Stevens and hosted by
lacquer crackers Records, platters, waxings, discs. (Decharne)
Laff Box Invented by American sound engineer Charles Douglass (1910-2003) in 1953, it provided
canned laughter for TV programs, including I Love Lucy.
Lamarr, Hedy (1924-2000) Born Hedy Kiesler in Vienna, this Hollywood actress used her knowledge of
musical harmony, along with composer George Antheil, to obtain a patent on technology for military
communications in 1942, which established the groundwork for today's spread-spectrum communication
LAN (local area network) A combination of at least two computers and peripherals on a common wiring
scheme, which allows two-way communication of data between any devices on the network.
Laplace, Marquis Pierre Simon de (1749-1827) French mathematician and astronomer who formulated
the theory of probability.
Laplace transform Electronic circuit analysis. A powerful circuit analysis technique that transforms
difficult differential equations into simple algebra problems. Omitting all the mathematical details to get
to the essence, the Laplace transform substitutes the Laplace operator "s" to represent complex frequency
impedances. Therefore inductive reactance, XL is represented by "sL" and capacitive reactance, XC
becomes 1/sC.
larynx See: voice box.
laser (light amplification by stimulated emission of radiation) A device that generates coherent,
monochromatic light waves. All CD players contain a semiconductor laser in their optical pickup. (1 of 8) [10/3/04 12:30:13 AM]
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last-on Teleconferencing. Term referring to microphone inputs on an automatic mic mixer that stay on
(open) until another mic input turns on. Contrast with gated-on. A last-on mic becomes a master mic if
left open long enough.
latency Similar to propagation delay but broader in application. Used to describe the inherent delay in
signal processing as well as software processing. The time it takes for a system or device to respond to an
instruction, or the time it takes for a signal to pass through a device. It is how long it takes for a result to
happen from a command. In telecommunications it is the length of time it takes packets to traverse the
laugh box See: Laff Box
lavaliere or lavaliere microphone A small electret microphone designed to be worn on a person. The
first lavaliere mics were worn around the neck on a lanyard, hence the French name lavallière, a type of
necktie, used to describe a pendant worn on a chain around the neck [after the Duchesse de La Vallière
who started the fashion (AHD)]. Today most lavaliere (the final "e" is commonly dropped) mics are
attached by clips rather than hung from a cord.
lawful "Compatible with the will of a judge having jurisdiction." -- Ambrose Bierce.
lawyer "One skilled in circumvention of the law." -- Ambrose Bierce.
LCD (liquid crystal display) A display of numerical or graphical information made of material whose
reflectance or transmittance changes when an electric field is applied. An LCD requires ambient light or
backlighting for viewing.
LED (light emitting diode) Invented by Nick Holonyak, Jr. in 1962, a self-lighting semiconductor display
of numerical or graphical information based on the light emitting characteristics of a solid-state device
that emits incoherent (i.e., random direction) light when conducting a forward current. See LEVD
LeetInternet-based written slang, e.g., "leet" is Internet slang for "elite," "L8tr" for "later," and "l00kin6"
for "looking, etc. Used to encrypt text messages, but it is much more sophisticated than the elementary
"B4" for "before." It is a complicated use of letters and numbers that look like letters, e.g., "m4d" for
legacy devices Something handed down from an ancestor, or a predecessor, or something from the past
(AHD). Used in the computer world to refer to yesterday's solutions, for example including an RS-232
port on a USB machine.
LEO (low earth orbit) Telephony. Term referring to communications satellites positioned 200-900 miles
(320-1450 kilometers) high. (2 of 8) [10/3/04 12:30:13 AM]
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Leslie Loudspeaker. A special loudspeaker design made famous by its use with the Hammond B3 organ,
featured so prominently in much of the 1960's and 1970's music (Procol Harum, et al.) characterized by a
swirling pitch shifting sound. Designed in the 1940s by Don Leslie, it uses a fixed loudspeaker and a
rotating horn assembly to cause a doppler sound effect.
LEVD (light emitting vegetable diode) See Matt Reilly's "The Light Emitting Vegetable Diode" [Thanks
leveler A dynamic processor that maintains (or "levels") the amount of one audio signal based upon the
level of a second audio signal. Normally, the second signal is from an ambient noise sensing microphone.
For example, a restaurant is a typical application where it is desired to maintain paging and background
music a specified loudness above the ambient noise. The leveler monitors the background noise,
dynamically increasing and decreasing the main audio signal as necessary to maintain a constant loudness
differential between the two. Also called SPL controller.
levels Terms used to describe relative audio signal levels: (Also see decibel).
mic-level Nominal signal coming directly from a microphone. Very low, in
the microvolts, and requires a preamp with at least 60 dB gain before using
with any line-level equipment.
line-level Standard +4 dBu or -10 dBV audio levels. See decibel.
instrument-level Nominal signal from musical instruments using electrical
pick-ups. Varies widely, from very low mic-levels to quite large line-levels.
lexicographer The author of a lexicon or dictionary. "Every other author may aspire to praise; the
lexicographer can only hope to escape reproach; and even this negative recompense has been yet granted
to very few." -- Samuel Johnson, 1755.
LFE (low frequency effects) [Note: it is "effects" NOT "enhancement".) Populary called bass
management, but this is technically wrong (See M&K for a good discussion). The "point-one" in "5.1
surround systems". It refers to the limited bandwidth (20-90 Hz, 20-120 Hz, or 20-150 Hz depending on
the encoding system) special effects/feature channel, but can also refer to a subwoofer channel. Both
Dolby Digital and DTS Consumer use the term. The "bass management" part comes from having the
option of leaving the bass in the five full-range channels or sending all the lower bass to the subwoofer, or
some combination.
LFO (low frequency oscillator) Synthesizers. A very low frequency (less than 10 Hz) sine wave oscillator
used to slowly vary other parameters to create effects like flanging and tremolo, or vibrato.
licorice stick Clarinet. (Decharne) (3 of 8) [10/3/04 12:30:13 AM]
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lift/dip Popular European term meaning boost/cut.
limiter A compressor with a fixed ratio of 10:1 or greater. The dynamic action effectively prevents the
audio signal from becoming any larger than the threshold setting. For example, if the threshold is set for,
say, +16 dBu and the input signal increases by 10 dB to +26 dB, the output only increases by 1 dB to +17
dBu, essentially remaining constant. Used primarily for preventing equipment, media, and transmitter
overloads. A limiter is to a compressor what a noise gate is to an expander. See RaneNote: Limiters
Unlimited, RaneNote: Signal Processing Fundamentals, and RaneNote: Good Dynamics Processing
linearity error Electronics. The maximum permissible deviation of the actual output quantity from a
reference curve or line. Think of it as an error-window surrounding the reference: anywhere inside is
okay, anywhere outside is not. The size of the window is the linearity error.
line arrays Loudspeakers. (also called articulated line arrays) A vertical line (or linear) configuration
for large venue multi-cabinet loudspeaker systems creating tight (and steerable) beamwidth coverage
(degrees of arc for the propagating sound wave, vertically and horizonitally). Favored for their controlled
directivity that reduces room reflections and produces less reverberation and improved sound
intelligibility, as well as reducing the sound that bleeds back onto the performers. The three most popular
configurations are (a) uniform array: typically 2-8 boxes arranged in a flat straight line popular in smaller
venues and usually tilted downward above the audience; (b) constant splay array: forms a smooth arc by
tilting each box the same amount (pitch) resulting in a wider beamwidth popular in concert hall settings,
particularly those with balconies; (c) progressive splay array: combines both previous examples by
starting out with a straight flat array that gradually creates an arc at the lower end, forming the letter "J"
like shape. Popular for large arenas and concert settings. Individual and unique variations are offered by
all major loudspeaker companies. A few examples follow, however this a small sampling of the more than
25 loudspeaker array manufacturers -- apologies to those left out: EAW, EV, JBL, L-Acoustics,
McCauley, Meyer, Nexo, Renkus-Heinz, SLS, also see RLA (ribbon line arrays).
linear PCM A pulse code modulation system in which the signal is converted directly to a PCM word
without companding, or other processing.
linear phase response Any system which accurately preserves phase relationships between frequencies,
i.e., that exhibits pure delay. See: group delay
linear system or linear device A system or device that meets two criteria: 1) proportionality -- the output
smoothly follows the input; 2) additivity -- if input x results in output U and input y results in output V,
then input x+y must result in output U+V. This means the system or device is predictably and its cause
and effect relationship is proportional. Contrast: nonlinear.
linear taper See potentiometer (4 of 8) [10/3/04 12:30:13 AM]
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linear time code See time code
line driver A balanced output stage designed to interface and drive long lines. Long output lines tax
output stages in terms of stability and current demands. Designs vary from direct-drive differential
(sometimes using cross-coupled techniques) to transformer drive. See RaneNote: Practical Line Driving
Current Requirements.
line echo canceller See: echo canceller
line-level See levels.
Linkwitz-Riley crossover The de facto standard for professional audio active crossovers is the 4th-order
(24 dB/octave slopes) Linkwitz-Riley (LR-4) design. Consisting of cascaded 2nd-order Butterworth lowpass filters, the LR-4 represents a vast improvement over the previous 3rd-order (18 dB/octave)
Butterworth standard. Named after S. Linkwitz, a Hewlett-Packard engineer at that time, who first
described the problems and solution in his paper "Active Crossover Networks for Non-coincident
Drivers," J. Audio Eng. Soc., vol. 24, Jan/Feb 1976, pp. 2-8. In this paper, he credited his co-worker Russ
Riley for the idea that cascaded Butterworth filters met all his crossover requirements. Their effort
became known as the Linkwitz-Riley alignment. Linkwitz showed that a significant weakness of the
Butterworth design was the behavior of the combined acoustic lobe along the vertical axis. An acoustic
lobe results when both drivers operate together reproducing the crossover frequency band, and in the
Butterworth case it exhibits severe peaking and is not on-axis (it tilts toward the lagging driver). Linkwitz
showed that this results from the Butterworth outputs not being in-phase. Riley demonstrated an elegant
solution by cascading two 2nd-order (any even-ordered pair works) Butterworth filters, which produced
outputs that were always in-phase and summed to a constant-voltage response. Thus was created a better
crossover. See RaneNote: Linkwitz-Riley Crossovers, RaneNote: Linkwitz-Riley Crossovers up to 8thOrder and RaneNote: Signal Processing Fundamentals.
Linux A computer Unix-type operating system (OS) invented by Linus Torvalds in 1992, who wrote it as
a student at the University of Helsinki. He created this OS because he couldn't afford one that could
accomplish what he wanted with his available hardware. He then posted it on the network for other
students, where it grew and became very stable and powerful. Today, for free, the software, source code,
etc., is available off the Web.
listening "It is the province of knowledge to speak and it is the privilege of wisdom to listen." Oliver
Wendel Holmes (Crystal)
litz wire Derived and shortened from the German word "litzendraht" meaning strand, or woven wire. It is
a cable constructed of individually insulated magnet wires either twisted or braided into a uniform pattern,
which increases the total surface area compared to an equivalent solid conductor. The pattern is formed to (5 of 8) [10/3/04 12:30:13 AM]
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reduce skin effect by guaranteeing that along a significant length, any single conductor will be, for some
portion of its length, located in the center, the middle, and the outer portion of the bundle. This
transposition prevents any one conductor from being subject to the full forces of magnetic flux, thereby
reducing the effective resistance of the entire bundle. Litz wire bundles of 50, 100 or even more
conductors are available. They are constructed by winding smaller bundles of six conductors into larger
bundles. Those bundles may be "litzed" with other bundles to create progressively larger cables. Litz
constructions counteract skin effect by increasing the amount of surface area without significantly
increasing the size of the conductor.
lobing error Electronic crossovers. The amount of on-axis deviation in amplitude from zero (i.e., perfect
combined radiation pattern) resulting from phase deviations at the crossover point. Term coined by
Lipshitz (Lipshitz, Stanley P. and John Vanderkooy, "A Family of Linear-Phase Crossover Networks of
High Slope Derived by Time Delay," J. Audio Eng. Soc., Vol. 31, No. 1/2, January/February 1983, pp. 220). See RaneNote: Linkwitz-Riley Crossovers.
log Short for logarithm
logarithm Mathematics. A shortcut method that uses the powers of 10 (or some other base) to represent
the actual number. The logarithm is the power to which a base, such as 10, must be raised to produce a
given number. For example, 10³ = 1,000; therefore, log (to the base 10) 1,000 = 3. The types most often
used are the common logarithm (base 10), the natural logarithm (base e), and the binary logarithm (base
log taper See potentiometer
Long, Richard (1933-1986) Founder of RLA (Richard Long and Associates), dance club sound
designers during the disco heydays of the '70s and '80s. Richard's success grew out of his experience
working as the sound engineer for the Paradise Garage in Greenwich Village during the mid-seventies.
After developing his chops at the Paradise Garage, Richard designed many famous dance clubs including
Studio 54, Annabel's (London), Regine's (a chain of 19 clubs scattered around the world from Paris and
NY to Cairo) and many others that were the vanguard of the disco era. Indeed, continuing years beyond
Richard's unfortunate death in 1986, his designs flourish today in such icons as the Ministry of Sound
(London). Further information available at GSANY and see Richard and Alan Fierstein's seminal paper
"State-of-the-Art Discotheque Sound Systems -- System Design and Acoustical Measurement," presented
at the 67th Convention of the Audio Engineering Society, New York , 1980, preprint 1694.
Lorentz force The orthogonal (right angle) force on a charged particle traveling in a magnetic field,
named after H. A. Lorentz. (AHD)
Lorentz, Hendrik Antoon (1853-1928) Dutch physicist, famous for the Lorentz force and co-receiving a
Nobel Prize for researching the influence of magnetism on radiation. (AHD) (6 of 8) [10/3/04 12:30:13 AM]
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loss See: gain.
lossy See: digital audio data compression
loud Having offensively bright colors: a loud necktie. (AHD)
loudness The SPL of a standard sound which appears to be as loud as the unknown. Loudness level is
measured in phons and equals the equivalent SPL in dB of the standard. [For example, a sound judged as
loud as a 40 dB-SPL 1 kHz tone has a loudness level of 40 phons. Also, it takes 10 phons (an increase of
10 dB-SPL) to be judged twice as loud.]
loudness curve See: Fletcher-Munson.
loudspeaker Dynamic. An electromagnetic transducer based on the principle of electromagnetic
induction used to convert the electrical energy output of a power amplifier into acoustic energy. The heart
of a dynamic loudspeaker is a coil of wire (the voice coil), a magnet, and a cone. The amplifier applies
voltage to the voice coil causing a current to flow that produces a magnetic field that reacts with the
stationary magnet making the cone move proportional to the applied audio signal.
Other loudspeaker technologies exist, among these are electrostatic (a thin sheet of plastic film suspended
between two wire grids or screens; the film is conductive and charged with a high voltage; the film is
alternately attracted to one grid and then the other resulting in motion that radiates sound), but for pro
audio applications, dynamic loudspeakers dominate. See also ribbon tweeter and back-emf
Loudspeaker Health Care Fun and educational tips developed by MC2 System Design Group. [Check it
out, you won't be disappointed.]
loudspeaker line arrays See: line arrays
loudspeaker model See: amplifier dummy load
loudspeaker reconing See: reconing
loudspeaker sensitivity See: sensitivity
loudspeaker surround See: surround
low-cut filter See: high-pass filter [In audio electronics, we define things like this just to make sure you're
paying attention.] Contrast with low-pass filter below. (7 of 8) [10/3/04 12:30:13 AM]
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low-pass filter A filter having a passband extending from DC (zero Hz) to some finite cutoff frequency
(not infinite). A filter with a characteristic that allows all frequencies below a specified rolloff frequency
to pass and attenuate all frequencies above. Anti-aliasing and anti-imaging filters are low-pass filters.
Also known as a high-cut filter.
L-pad See attenuator pad.
LRC (inductance-resistance-capacitance) Electronics. Shorthand for the most common passive circuit
elements. Also seen as RLC, LCR, CRL, etc.
LSB (least significant bit) The bit within a digital word that represents the smallest possible coded value;
hence, the LSB is a measure of precision.
LTC (linear time code) See time code
Lully, Jean-Baptiste (1632-1687) French composer. (AHD)
The baton used by a seventeenth-century conductor was a much longer and heavier affair
than the little wand used today. On January 8, 1687, in the course of conducting a Te
Deum, Lully struck his foot with his baton, injuring it so seriously that gangrene set in and
he died ten weeks later. [Bartlett's Book of Anecdotes]
luminance 1. Abbreviated Y. That part of the video signal that carries the information on how bright the
TV signal is to be. The black and white signal. 2. VJ Jargon. A filter that controls the video brightness.
Used to blend clips by limiting the bright or dark image pixels. (See: chrominance.)
lyre A stringed instrument of the harp family having two curved arms connected at the upper end by a
crossbar, used to accompany a singer or reciter of poetry, especially in ancient Greece. (AHD) One of the
oldest known musical instruments dating back to the Sumerians.
lyric French word literally meaning of a lyre; the words of a song.
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MAC Address (Medium Access Control Address) (Also called MAC Name) Computer Networks. The
(usually) 48-bit hardware address number unique to each LAN NIC (put there by the manufacturer),
which identifies every network node.
macintosh (also mackintosh) Chiefly British A raincoat or a lightweight, waterproof fabric that was
originally of rubberized cotton. [After Charles Macintosh (1766-1843), Scottish inventor] (AHD)
MADI (multichannel audio digital interface) An AES recommended practice document Digital Audio
Engineering - Serial Multichannel Audio Digital Interface (MADI) AES-10-1991 (ANSI S4.43-1991)
specifying and controlling the requirements for digital interconnection between multitrack recorders and
mixing consoles. The standard provides for 56 simultaneous digital audio channels that are conveyed
point-to-point on a single coaxial cable fitted with BNC connectors along with a separate synchronization
signal. Fiber optic implementation is specified in document AES-10id-1995, entitled AES information
document for digital audio engineering - Engineering guidelines for the multichannel audio digital
interface (MADI) AES 10. Basically, the technique takes the standard AES/EBU interface and multiplexes
56 of these into one sample period rather than the original two.
magic "An art of converting superstition into coin. There are other arts serving the same high purpose,
but the discreet lexicographer does not name them." -- Ambrose Bierce.
MaGIC (Media-accelerated Global Information Carrier) An acronym trademark of Gibson Guitar
Corp. for their digital transport protocol.
magnet Physics. A body that produces a magnetic field external to itself. (IEEE)
magnetic field Physics. The electric field surrounding any current-carrying conductor. (IEEE) A
condition found in the region around a magnet or an electric current, characterized by the existence of a
detectable magnetic force at every point in the region and by the existence of magnetic poles. (AHD)
magnetic pickup See: pickup
magnitude 1. Mathematics. a. A number assigned to a quantity so that it may be compared with other
quantities. b. A property that can be quantitatively described, such as the volume of a sphere, the length (1 of 14) [10/3/04 12:30:18 AM]
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of a vector, or the value of a voltage or current waveform. (AHD)
Maine The only American state whose name is just one syllable.
mandolin rail A device installed within a piano used to create the classic ragtime honky-tonk sound
popularized in player pianos and nickelodeons. "The rail consists of a rod of wood spanning the strings of
an upright piano. Fringed leather hangs from the rod. Each fringe is approximately two inches long and
half an inch wide. Although steel buttons were often used, brass buttons affixed to the string side of the
leather worked best. The rail was usually hinged to pivot upward when not in use or to pivot down when
in use. The felt from the piano hammer will hit the leather fringe, knocking the brass button against the
piano string. The result is a metallic, honky-tonk piano sound." -- Howard Byrne, Assistant Curator, The
Music House Museum, Acme, MI.
mantissa The fractional part of a logarithm, e.g., in the logarithm 1.83885, the mantissa is 0.83885. (The
integer part of a number is called the characteristic. In the example the characteristic is 1.) Floating-point
arithmetic also calls this the significand.
Marconi, Guglielmo (1874-1937) Italian engineer and inventor who in 1901 transmitted long-wave
radio signals across the Atlantic Ocean and opened the door to a rapidly developing wireless industry. In
1909 he won the Nobel Prize in physics, shared with Karl Ferdinand Braun whose modifications to
Marconi's transmitters significantly increased their range and usefulness. (AHD)
mask or masking Psychology of Hearing. The human hearing phenomenon where the response to one
stimulus is reduced in the presence of another, i.e., two sounds arrive but only one sound is heard.
Particularly evident when one sound is louder than another, with the result being that we hear the louder
sound, even if arriving at a slightly different time. Frequency plays a part: a louder sound heard at one
frequency prevents softer sounds near that frequency from being heard. However, not all frequencies
mask the same. Mid-band frequencies mask far better than low frequencies, for example. Related to
critical bands. Also see: temporal masking (e.g., forward and backward masking).
Massa, Frank (1906-1990) American engineer who is considered the father of modern electroacoustics
for developing the fundamental technology that became the foundation for electroacoustics. He is the
recognized pioneer in the design of transducers and systems for both air and underwater applications, as
well as the founder of Massa Products Corporation. The Frank Massa and Harry Olson authored the first
textbook on electroacoustics, Applied Acoustics, in 1934. See Fundamentals of Electroacoustics for
further details.
mastering Audio recording. The final step in the recording process, completed before the replication or
streaming process. The act of creating the master from which all copies will be made. The following lists
many of the required artistic and technical steps, although some of these are more accurately referred to
as pre-mastering steps leading to a preliminary master used to create the final production master. (2 of 14) [10/3/04 12:30:18 AM]
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Transfer the recording into the highest digital (or analog) format for the
mastering steps.
Fix unwanted noise problems, either captured during the recording process,
or for restoration archival purposes.
Edit and apply signal processing as required to optimize timbre, clarity,
smoothness and impact.
Maximize the stereo or surround-sound balance and spread.
Maximize and smooth out differences in song levels.
Add pre-emphasis equalization if required for the duplication media.
Add ISRC and other subcodes as required.
Sequence the songs into their optimum playing order.
Create fade-ins, fade-outs, segues and spacing between songs.
Hide bonus tracks by using creative subcoding, if requested.
Format and transfer the final results to the required media for duplication.
And sometimes, create the package artwork.
Or, as DRT Mastering succinctly puts it: "Mastering creates a seamless whole out of a
collection of individual tracks."
master mic Teleconferencing. Term referring to the microphone input on an automatic mic mixer that is
the last to detect audio. A last-on mic becomes a master mic only if left open long enough.
master port Teleconferencing. Term referring to the audio input port that is the last to detect audio.
matrix-encoding Audio. A technique of storing more than two audio channels on a two-channel medium
or transmission format. Dolby Surround is an example, where the center and surround channels are
electronically encoded into the left and right channels of a stereo signal (usually by broadband 90° phase
shifting and summing). On playback, the center and surround channel are decoded from the left and right
signals. The problem inherent with matrix-encoding is the mathematical dilemma of trying to solve for
four unknowns (left, right, center & surround) when you only have two equations (the stereo signal); you
can get close but you cannot get the exact right answer (so you always have crosstalk). This contrasts
with today's discrete digital channels.
matrix-mixer Similar to the matrix switcher (or router) below, but with additional signal processing
features on all the inputs and outputs. With a matrix-mixer, not only can you assign any input to any
output but you may add EQ, compression, change level, etc. Very elaborate models exist with as many as
32-channels in and 8 or more output channels (and as big as a Volkswagen). Also see: mix-minus.
matrix switcher See router.
maverick Being independent in thought and action or exhibiting such independence. Believed after (3 of 14) [10/3/04 12:30:18 AM]
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Samuel Augustus Maverick (1803-1870), American cattleman who left the calves in his herd unbranded.
maximally flat magnitude response See: Butterworth crossover
maximally flat phase response See: Bessel crossover
MAU (multistation access unit) See token ring.
Mbps (million bits per second) (always lower-case b) A popular measure of transmission speed, but
should be Mibps, or mebi bits per second. See: mebi
MBps (million bytes per second) (always upper-case B) A popular measure of transmission speed, but
should be MiBps, or mebi bytes per second. See: mebi
MD (MiniDisc) Trademark term for the Sony digital audio recordable optical storage system utilizing
data compression to reduce disc size.
MDM (modular digital multitrack) Generic term used to describe any of the families of digital audio
multitrack recorders. The most common examples being the Alesis ADAT series and the Tascam DA-88
mebi Symbol Mi New term standardized by the IEC as Amendment 2 to IEC 60027-2 Letter Symbols to
be Used in Electrical Technology to signify binary multiples of 1,048,576 (i.e., 2E20). Meant to
distinguish between exact binary and decimal quantities, i.e., 1,048,576 verses 1,000,000. For example, it
is now 16 mebibits, abbreviated 16 Mib, not 16 megabits or 16 Mb.
media converter or media manager The ability to manage and the process of managing different media
(coaxial cable, twisted-pair cable, and fiber-optics cable) used within the same network. Media
management involves cable performance monitoring, cable break detection, planning for cable routes, as
while as converting data signals between the various media.
medical conferencing See telemedicine.
medium 1. In telecommunications, the transmission path along which a signal propagates, such as a
twisted-pair, coaxial cable, waveguide, fiber optics, or through water, or air. 2. The material on which
data are recorded, such as plain paper, paper tapes, punched cards, magnetic tapes, magnetic disks, or
optical discs.
mega- 1. A prefix signifying one million (10E6). abbreviated M. 2. A prefix popularly used in computer (4 of 14) [10/3/04 12:30:19 AM]
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work to signify multiples of 1,048,576 (i.e., 2E20), but should use mebi. .
megabyte Popular term meaning a million bytes but should be mebibytes. See mebi
megaflops See: MFLOPS
mel filter See: MFCC.
Mesa filter Term coined by Lake Technology Ltd for their Lake Contour EQ technology.
metadata Data about data. See: Michael Day, "Metadata in a Nutshell," and "Demystifying Audio
Metadata," J. Audio Eng. Soc., Vol. 51, No. 7/8, pp 744-751, July/Aug 2003.
MEMS (microelectromechanical systems) The acronym says it all. Check out this clearinghouse website
for the latest info.
meter ballistics Term describing the response characteristics of a meter indicator. Applies to all meters
from original iron vane, taut-band or pivot & jewel mechanical analog designs to LED, LCD or plasma
ladder arrays. Two universal standards exist for audio use: the VU meter and the PPM (peak program
meter). The indicator attack (or rise) times are specified as well as the decay (or fall) rates along with the
recommended detector method.
MFCC (mel-filtered cepstral coefficients) An important analysis parameter in CBID systems. These
coefficients describe the harmonic spectrum shape perceived by the human auditory system, i.e., they
characterize the shape of sound. For details, see white paper by Audible Magic, one of the leaders in
CBID systems.
MFLOPS (pronounced "mega-flops") (million floating point operations per second) A measure of
computing power.
MI (musical instrument) A broad term used to describe the musical instrument marketplace in general.
Reference is made to "the MI market," or to a specific "MI store." If a store sells band instruments, for
instance, it is an MI store.
mic-level See levels.
micro- Prefix for one millionth (10E-6), abbreviated µ.
microbar 1. A unit of pressure equal to one millionth of a bar. 2. A really small place to have a beer. (5 of 14) [10/3/04 12:30:19 AM]
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microcontroller See: microprocessor
micron A deprecated unit of measure equal to a micrometer, one-millionth of a meter. No longer used.
microphone An electroacoustic transducer used to convert the input acoustic energy into an electrical
energy output. Many methods exist; see, for example, electret microphone, condenser microphone, and
dynamic microphone.
microphone sensitivity See sensitivity
microphonic General. Any noise cause by mechanical shock or vibration of elements in a system (IEEE
Std 100). Audio. Electrical noise caused by mechanical or audio induced vibration of the object. Common
examples are vacuum tubes where mechanical vibration of the tube causes modulation of the electrode
current, and capacitors that induce noise when tapped or vibrated in any manner.
microprocessor An integrated circuit that performs a variety of operations in accordance with a list of
instructions. The core of a microcomputer or personal computer, a one chip computer.
Microsoft® (microcomputer software) Founded by Bill Gates and Paul Allen in 1975, whose
relationship began with their first business venture named Traf-O-Data.
mic splitter A phrase first coined by Franklin J. Miller, founder of Sescom, to describe a box fitted with
female (inputs) and male (outputs) XLR mic connectors that allowed mic inputs to be routed to two, or
more outputs. Usually passive, either hard-wired, or transformer connected. One common usage is for onstage mic splitting, where one output goes to the monitor mixer and one to the FOH mixer.
middle C Music. The tone represented by a note on the first ledger line below a treble clef or the first
ledger line above a bass clef. It is the first C below international pitch. [AHD] The pitch equals 523.5 Hz
and is the MIDI note number 60.
MIDI (musical instrument digital interface) Industry standard bus and protocol for interconnection and
control of musical instruments. First launched in 1983, now generalized and expanded to include signal
processing and lighting control. See MMA
MIDI show control A term originally created by Charlie Richmond (Richmond Sound Design) to
describe a new form of MIDI control designed for live theater venues. His efforts resulted in the official
MIDI Show Control (MSC) specification. This document states: "The purpose of MIDI Show Control is
to allow MIDI systems to communicate with and to control dedicated intelligent control equipment in
theatrical, live performance, multi-media, audio-visual and similar environments." (6 of 14) [10/3/04 12:30:19 AM]
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MIDI time code See time code
military music "Military justice is to justice what military music is to music." -- Groucho Marx [from
Miller effect Electronics. The input impedance, and hence frequency response, of an inverting voltage
amplifier stage is strongly affected by the feedback from the output to the input. This effect was first
described by John M. Miller in his paper, "Dependence of the input impedance of a three-electrode
vacuum tube upon the load in the plate circuit," Scientific Papers of the Bureau of Standards Vol. 15, pp.
367-385, 1920. This effect is used often in power amplifiers and op amps to set the frequency response
and guarantee stability by forcing a single-pole (6 dB/octave, 90 degree phase shift) roll-off. Analog
power amplifiers in their simplest form consist of an input differential pair that produces a single-ended
output to drive a class A common-emitter amplifier voltage gain stage, followed by a push-pull emitter
follower current gain class AB output stage. If a single capacitor is connected between the base and
collector of the class A stage (called the "Miller capacitor") it will create a stable dominate pole for the
entire amplifier. In this circuit the effect described by Miller acts as a capacitance multiplier, allowing a
small capacitor to set the overall response.
milli- Prefix for one thousandth (10E-3), abbreviated m.
Minifon An early portable dictating machine developed in the 1950s using wire recorder technology. An
example of "dead recording media."
minimum-phase filters Electrical circuits From an electrical engineering viewpoint, the precise
definition of a minimum-phase function is a detailed mathematical concept involving positive real
transfer functions, i.e., transfer functions with all zeros restricted to the left half s-plane (complex
frequency plane using the Laplace transform operator s). This guarantees unconditional stability in the
circuit. For example, all equalizer designs based on 2nd-order bandpass or band-reject networks have
minimum-phase characteristics. Acoustics A term used to mean a linear phase (or phase linear, European
term) system. See: group delay and RaneNote: Exposing Equalizer Mythology.
MIPS (million instructions processed per second) A measure of computing power.
mix-minus A specialized matrix-mixer where there is one output associated with each input that includes
all other inputs except the one it is associated with. (The output is the complete mix, minus the one input.)
In this manner, the simplest mix-minus designs have an equal number of inputs and outputs (a square
matrix). For example, if there were 8-inputs, there would be 8-outputs. Each output would consists of a
mix of the seven other inputs, but not its own. Therefore Output 1, for instance, would consist of a mix of
Inputs 2-8, while Output 2 would consist of a mix of Inputs 1 & 3-7, Output 3 would consist of a mix of
Inputs 1,2 & 4-7, and so on. Primary usage is large conference rooms, where it is desirable to have the
loudspeaker closest to each microphone exclude that particular microphone, so as to reduce the chance of (7 of 14) [10/3/04 12:30:19 AM]
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feedback. See RaneNote: Mix-Minus Speech Reinforcement with Conferencing
mixer At its simplest level, an audio device used to add (combine or sum) multiple inputs into one or two
outputs, complete with level controls on all inputs. From here signal processing is added to each of the
inputs and outputs until behemoth monsters with as many as 64 inputs are created -- at a cost of around
10-20 kilobucks per input for fully digitized and automated boards. At these price points a mixer
becomes a recording console.
mLAN (music local area network) A technology developed and licensed by Yamaha based on the IEEE
1394 standard. It is a high-level multichannel audio, video and MIDI networking and connectionmanagement protocol.
MLP (Meridian Lossless Packing) A lossless audio coding scheme developed by Meridian Audio Ltd..
MLP has been selected as the optional coding scheme for use on DVD-Audio, as well as other
transmission, storage and archiving applications. It is a true lossless coding technology, in that the
recovered audio is bit-for-bit identical to the original. Unlike perceptual or lossy data reduction, MLP
does not alter the final decoded signal in any way, but merely "packs" the audio data more efficiently into
a smaller data rate for transmission or storage. It is simple to decode and requires relatively low
computational power for playback.
MLS (maximum-length sequences) A time-domain-based analyzer using a mathematically designed test
signal optimized for sound analysis. The test signal (a maximum-length sequence) is electronically
generated and characterized by having a flat energy-vs.-frequency curve over a wide frequency range.
Sounding similar to white noise, it is actually periodic, with a long repetition rate. This test signal is most
often tailored to be pink noise, as the preferred response for fractional octave analysis. Similar in
principle to impulse response testing - think of the maximum-length sequence test signal as a series of
randomly distributed positive- and negative-going impulses. See: MLSSA
MLSSA (pronounced "Melissa") (maximum-length sequences system analyzer) Trademarked name for
the first MLS measurement instrument designed by DRA Laboratories (Sarasota, FL). M.R. Schroeder
used maximum-length-sequences methods for room impulse response measurement in 1979 (based on
work dating back to the mid-60's); however, it was not until 1987 that the use of MLS became
commercially available. The first MLS instrument was developed and made practical by Douglas Rife,
who described the principles in his landmark paper (co-authored by John Vanderkooy, University of
Waterloo) "Transfer-Function Measurement with Maximum-Length Sequences" (J. Audio Eng. Soc., vol.
37, no. 6, June 1989), and followed up with new applications described in "Modulation Transfer Function
Measurement with Maximum-Length Sequences" (J. Audio Eng. Soc., vol. 40, no. 10, October 1992).
MMA (MIDI Manufacturers Association) The original source for information on MIDI technology,
where companies work together to create the standards upon which MIDI compatibility is built. (8 of 14) [10/3/04 12:30:19 AM]
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MMCD (multimedia compact disc) See: DVD
MMVF (multimedia video file) See: DVD
modal Acoustics. Of, relating to, or characteristic of a room mode or modes. (AHD)
modes Shorten form of room modes.
modem (modulator-demodulator) A peripheral device used to convert digital signals ("1s" and "0s") into
analog signals (tones) and vice versa, necessary for communication using standard telephone lines.
mojo 1. A charm or amulet thought to have magic powers. 2. Slang: power, luck, etc., as of magical or
supernatural origin. 3. Mojo Series Rane Corporation trademark for their series of economical products
designed for high quality performance and reliability aimed at the working musician. 4. Abbr. Mother
Jones magazine, or reference to their Internet news network: The Mojo Wire.
MOL (maximum output level) Magnetic tape. The maximum output level of a magnetic tape is defined
as the magnetization level at which a recorded kHz sine wave reaches 3% third-harmonic distortion (note
that is 3% THIRD-harmonic distortion -- not 3% TOTAL harmonic distortion). Also referred to as 3%
distortion of the musical twelfth. See third-harmonic distortion
monaural See mono
mondegreen The term for representing a series of words resulting from the mishearing of a statement or
song lyric. Variously attributed to Sylvia Wright, who is credited with coining the word in a 1954
Harper's column, and also to Jon Carroll by Pinker.
Monitor World Live sound. Area of the live sound stage where the monitor engineer mixes his/her
magic and attempts to decipher cryptic hand signals from the performers. Not to be confused with "GuitarTech-Land", where all the babes hang out.
monitor mixer A mixer used to create the proper signals to drive the individual musician stage
loudspeaker monitors. Also called foldback speakers. Compare: FOH
mono Shorten form of monophonic, or monaural, relating to a system of transmitting, recording, or
reproducing sound in which one or more sources are connected to a single channel; monaural. [AHD]
Compare to stereo.
mono 3-way, etc. See: active crossover (9 of 14) [10/3/04 12:30:19 AM]
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monophonic See mono
monopole woofer system Loudspeakers. Literally "one pole," the most common form of woofer system
that acts like an omnidirectional sound source, thus exciting room modes more than the alternative dipole
woofer systems.
monotonic Mathematics. Designating sequences, the successive members of which either consistently
increase or decrease but do not oscillate in relative value. Each member of a monotone increasing
sequence is greater than or equal to the preceding member; each member of a monotone decreasing
sequence is less than or equal to the preceding member. (AHD)
month One of the words in the English language without a rhyme -- some others are "orange," "purple"
and "silver."
Moog synthesizer The first electronic keyboard invented by US engineer Robert A. Moog in
collaboration with composer Herbert A. Deutsch. Introduced in 1964, but not made popular until Walter
(Wendy) Carlos released the megahit album Switched-On Bach in 1968. For the complete and delightful
history see Pinch, Trevor & Frank Trocco, Analog Days: The Invention and Impact of the Moog
Moore's Law 1. Named after Gordon Moore, a cofounder of Intel, who wrote in an Electronics
magazine article in 1965, that computer chip complexity would double every twelve months for the next
ten years. Ten years later his forecast proved to be correct. At that time, he then predicted that the
doubling would happen every two years for the next ten years. Ten years later, he was, once again, proved
correct. By combining the two predictions, Moore's Law is often stated as a doubling every 18 months. 2.
The dictum that requires you to buy a new computer every two years. [Thanks DC.]
MOR (magneto-optical recording) An erasable optical disc system using magnetic media and laser
MOSFET (metal-oxide semiconductor field-effect transistor) See FET
motional feedback See: servo-loop
moving coil Transducers. A type of electromagnetic transducer that operates by having a mechanical
device move a coil of wire in a magnetic filed to convert the mechanical movement into an electrical
current. Contrast with moving magnet.
moving magnet Transducers. A type of electromagnetic transducer that operates by having a mechanical
device move a magnet in a coil of wire to convert the mechanical movement into an electrical current. (10 of 14) [10/3/04 12:30:19 AM]
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Contrast with moving coil.
Mozart, Wolfgang Amadeus (1756-1791) Austrian composer.
Mozart was approached by a young man, little older than a boy, who sought his advice on
composing a symphony. Mozart pointed out that he was still very young and it might be
better if he began by composing ballads. "But you wrote symphonies when you were only
ten years old," objected the lad. "But I didn't have to ask how," Mozart retorted. [Bartlett's
Book of Anecdotes]
MP3 (MPEG-1, Layer 3) A type of digital audio compression popularized for transmitting songs over
the Internet. MP3 allows real-time audio streaming for Internet encoding and downloading. MP3 files are
identified by the suffix ".MP3" Typically MP3 compresses CD-quality audio down to about one minute
per 1MB file size. Also see Wired magazine's MP3 site.
MPEG (Moving Picture Experts Group) A working group within SMPTE who set, among other things,
specifications for compression schemes for audio and video transmission. A term commonly used to
make reference to their image-compression scheme (MPEG-2) for full motion video.
MPEG-4 Structured Audio This specifies a set of tools that allow powerful and flexible description of
sound in a variety of ways, all based on what has become known as "structured audio," meaning
transmitting sound by describing it rather than compressing it.
MPGA (Music Producers Guild of the Americas) The original professional guild for music producers
and audio recording engineers, however in 2000, the Recording Academy absorbed it and established the
Producers & Engineers Wing.
MR (magnetoresistive) A technology based on the effect where electrical resistance in a material
changes when brought in contact with a magnetic field
M/S or M-S (mid-side or mono-stereo) microphone technique. Developed in the mid '50s by the Danish
radio engineer Holger Lauridsen (H. Lauridsen & F. Schlegel, "Stereophonie und richtungsdiffuse
Klangwiedergabe," Gravesaner Blätter, 1956, Nr. V, August, S.28-50) , a method for capturing
stereophonic sound using two microphones. One microphone with a cardioid response (although any
polar pattern will work) is aimed straight ahead toward the sound source (this is the mid or mono M part),
and a second microphone with a figure-8 (or bipolar) response is placed so that the two lobes are directed
toward the sides (this is the side or stereoS part). The two signals are then combined using an M-S
matrix circuit that yields two signals: M+S and M-S. See Streicher & Everest for complete details. (11 of 14) [10/3/04 12:30:19 AM]
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M/S matrix See M/S above.
MS-DOS® (Microsoft® disk operating system) Microsoft's registered trademark for their PC operating
MSB (most significant bit) The bit within a digital word that represents the biggest possible single-bit
coded value.
MSM (mid-side-mid, also called Double MS) An extension of the M-S microphone technique using two
coincident M-S pairs sharing the same side-facing figure-of-eight microphone, one pairing for the Front
L and R and the other pairing for the surrounds Ls and Rs (from Mike Skeet's article "MSM Mic
Surround Technique," Audio Media, May 2003, pp. 58-59.
MSPS (million samples per second) A measurement of data converter speed.
MTC (MIDI time code) See time code
mult Recording. Slang shortened form for "multiplex" or "multiple." Refers to routing or splitting signals
to multiple destinations. Found on patchbays where several "mult" jacks make a signal available to many
multicasting See: broadcasting.
multi-denomial transpedance informer Term coined by Jensen Transformers for their mythical
product, the JE-EP-ERs, first introduced in 1987, which almost changed the whole audio transformer
industry. The Jensen JE-EP-ERs pioneered the use of triple electonomic shielding and intrinsic eddybreeding, until outlawed by Congress in 1988. Voluntarily discontinued when their stock of zeta-metal
ran out, preventing any further use of interstage transpedance informance. Considered by many to be the
only necessary accessory when coupling a Rane PI 14 Pseudoacoustic Infector to a Crown Belchfire® BF6000SUX amplifier for playback using an Electro-Voice Rearaxial Softspeaker.
multimedia Generally refers to personal computers capable of multiple forms of communication
methods. These constitute a minimum combination of stereo audio, video, text, and graphics, plus the
more complex system includes fax and telephony provisions.
multing See mult
multipath Broadcast. Short for "multipath interference" or "multipath distortion." Interference due to
multiple arrivals of the same broadcast signal due to reflections off buildings (usually). The difference in
path lengths creates different arrival times thus causing signal cancellation and degradation. Most
commonly occurs in FM and TV broadcast signals. The experience in car audio FM systems is static and (12 of 14) [10/3/04 12:30:19 AM]
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signal weakening heard while slowing down and stopping; the signal comes and goes, weakens and
distorts then clears, creating a phenomena called "picket fencing." Since AM broadcast frequencies are
lower in frequency the wavelengths are longer and multipath does not occur.
multiplex To interleave two or more signals into a single output; a process of selecting one of a number
of inputs and switching its information to the output.
multipoint conference Telecommunication term referring to conferencing between three or more sites.
Murphy, Edsel and Murphy's Law The dictum that if anything can go wrong, it will. For the full
treatment see: "The Contributions of Edsel Murphy to the Understanding of the Behaviour of Inanimate
Objects," by D.L. Klipstein. This momentous presentation is believed to have been first published in
EEE, vol. 15, no. 8, August 1967. [EEE (Electronic Equipment Engineering) magazine morphed into
today's EDN (Electronic Design News) magazine.]
musical twelfth The third-harmonic of a tone, which equals one octave and a fifth -- hence, twelfth (12
not 13 because you don't count the original tone).
MUSICAM (masking pattern adapted universal sub-band integrated coding and multiplexing) A
flexible bit rate reduction standard for high quality audio. Jointly developed for digital audio broadcast by
CCETT in France, IRT in Germany and Philips in the Netherlands.
músick Defined by Samuel Johnson in his magnus opum, A Dictionary of the English Language,
published in 1755, as "The science of harmonical sounds."
music temperament See temperament
music vs. noise 1. "The sensation of a musical tone is due to a rapid periodic motion of the sonorous
body; the sensation of a noise to non-periodic motion." from On the Sensation of Tone (1862) Hermann
Helmholtz. 2. "Of all noises, I think music is the least disagreeable." -- Samuel Johnson [from Barber]
mutual coupling See: coupling.
mute A control found on recording consoles, some mixers, and certain signal processing units that
silences (mutes) a signal path, or output. Various uses.
Muzak (music + Kodak) 1. Trademark of the business music company founded in 1928 by General
George Owen Squier who patented the transmission of background music (phonograph records played
through the telephone system). He created the name by merging the word "music" with that of his
favorite high-tech venture, the Eastman Kodak Company. The word "Kodak" was coined by Eastman (13 of 14) [10/3/04 12:30:19 AM]
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himself, and in 1888 he first registered it as a trademark. According to Eastman, he invented it out of thin
air. He explained: "I devised the name myself. The letter "K" had been a favorite with me - it seems a
strong, incisive sort of letter. It became a question of trying out a great number of combinations of letters
that made words starting and ending with 'K.' The word 'Kodak' is the result." 2. "I worry that the person
who thought up Muzak may be thinking up something else." -- Lily Tomlin [from Barber]
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NAB (National Association of Broadcasters) A professional trade organization for people working in the
radio and television industry.
NAMM (National Association of Music Merchants is the original name; today it is officially the
International Music Products Association but they didn't change the acronym) A professional trade
organization for people working in the music business -- primarily in retailing and manufacturing of
music making products.
nano- A prefix for one billionth (10E-9), abbreviated n.
NAPRS (Nashville Association of Professional Recording Services) Established in 1995 to promote
Nashville's finest recording studios, services and engineers worldwide.
NARAS (National Academy of Recording Arts & Science) See The Recording Academy.
NARM (National Association of Recording Merchandisers) An industry organization made up
primarily of music retailers acting as an advocate body for the common interests of merchandisers and
distributors of music to industry and public policy makers.
narrow-band filter Term popularized by equalizer pioneer C.P. Boner to describe his patented (tapped
toroidal inductor) passive notch filters. Boner's filters were very high Q (around 200) and extremely
narrow (5 Hz at the -3 dB points). Boner used 100-150 of these sections in series to reduce feedback
modes. Today's usage extends this terminology to include all filters narrower than 1/3-octave. This
includes parametrics, notch filter sets, and certain cut-only variable equalizer designs.
National Electrical Code See: NEC
National Recording Registry Set up by Congress in 2002 to preserve historical recordings. The
inaugural list of recognized recordings includes "The Message," by Grandmaster Flash and the Furious
Five. (1982)
natural logarithm A logarithm based on the powers of e (aka Base-e). (1 of 8) [10/3/04 12:30:22 AM]
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N curve (normal curve) Same as Academy curve
NC (noise criterion) curves A unit of measurement for the ambient or background noise level of
occupied indoor spaces, i.e., a measure of its noisiness -- true story; real word. The measured noise
spectrum (done in octave bands using an SPL meter) is compared against a series of standard noise
criteria (NC) curves to determine the "NC level" of the space. The standard NC curves take into account
the equal loudness contours of Fletcher-Munson to accurately reflect the listening experience. Each NC
curve is assigned a number (in 5 dB increments) corresponding to the octave band SPL measured over the
octave centered at approximately 1500 Hz. A space is then said to have a background noise level of "NC20," for instance, which would be very quiet, comparable to a quality recording studio. Compare with RC
near end Telecommunication term referring to your end; the local room, as opposed to the far end.
near-end crosstalk Crosstalk that is propagated in a disturbed channel in the direction opposite to the
direction of propagation of the signal in the disturbing channel. The terminals of the disturbed channel, at
which the near-end crosstalk is present, and the energized terminal of the disturbing channel, are usually
near each other.
near field or near sound field The sound field very close to the sound source, between the source and the
far field. Technically, a distance less than one wavelength at the frequency of interest.
near-field monitor A loudspeaker used at a distance of 3-4 feet (1-1½ meters) in recording studios.
NEC (National Electrical Code) The name for the United States electrical safety standard (NFPA-70).
negative Electronics. An excess of electrons in a conductor or semiconductor.
negative feedback The act of comparing a fraction of the output signal to the input signal at the input to
an amplifier in such a way that the amplifier will keep this fraction of the output signal always exactly the
same as the input signal. Negative feedback is of prime importance in designing with opamps and audio
power amplifiers. As applied to audio amplifiers, negative feedback is first attributed to Bell Labs
scientist Harold S. Black, as described in the Bell Labs Technical Review, 1934 and his monumental 87
page U.S. patent 2,102,671 filed in 1932.
network Generally used to mean a multi-computer system (as opposed to a single computer bus-type
system) where multiple access is allowed from more than one computer at a time. Characterized by full
two-way (duplex) communications between all equipment and computers on the network. See CobraNet
for an example
network glossary See CobraNet's glossary for many useful terms. (2 of 8) [10/3/04 12:30:22 AM]
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Neumann, Georg (1891-1976) German inventor, entrepreneur and audio industry pioneer of high-quality
newton Abbr. N . The International System unit of force. It is equal to the force required to accelerate a
mass of one kilogram one meter per second per second.
Newton, Sir Isaac (1642-1727) English mathematician and scientist who invented differential calculus
and formulated the theory of universal gravitation, a theory about the nature of light, and three laws of
motion. The sight of a falling apple supposedly inspired his treatise on gravitation, presented in Principia
Mathematica (1687). (AHD)
NEXT (near-end crosstalk) Category wiring. Interference between signals on twisted pair cable caused
by damage (usually a loosening of the tight twist required for high speed transmission) occuring close to
the connector.
nibble A group of four bits or half a byte (8-bits).
NIC (network interface card) Ethernet. The PC expansion board that connects a device to a LAN,
usually Ethernet-based.
nickelodeon 1. An early movie theater charging an admission price of five cents. 2. A player piano. 3. A
jukebox. (AHD)
NIH (not invented here) Popular abbreviation found in technology land, used to described a prima donna
corporate attitude that everything they do must be original. Stems from an unheathy attitude that the only
solution worthy is their solution, thus rejecting ideas and inventions not theirs. Makes for very
unproductive and unhappy engineering teams.
noise General. Sound or a sound that is loud, unpleasant, unexpected, or undesired. Physics. A
disturbance, especially a random and persistent disturbance, that obscures or reduces the clarity of a
signal. Computer Science. Irrelevant or meaningless data. From Latin meaning nausea, discomfort and
seasickness. [AHD]
noise cancelling headphones Special headphones incorporating a microphone built into the headset that
samples the ambient sound and adds it back out-of-phase to the headphone signal. This method actively
cancels or nulls out background noise -- works best with high frequencies.
noise cancelling microphone A special dynamic microphone designed so both sides of the diaphragm are
exposed to the sound field. Close direct sound strikes primarily one side of the diaphragm causing it to
move while sounds from far away tend to be canceled because they strike the diaphragm from all sides (3 of 8) [10/3/04 12:30:22 AM]
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with no net force.
noise color People working in pro audio know the terms white noise and pink noise, but few recognize
the terms "azure noise" or "red noise," but they are real terms. Noise that is not white is called colored
noise and will have more energy at some frequencies than others, analogous to colored light.
White noise and pink noise are well defined and known; much less so are the others.
White noise is so named because it is analogous to white light in that it contains all audible frequencies
distributed uniformly throughout the spectrum. Passing white light through a prism (a form of filtering)
breaks it down into a range of colors. Examination shows that red light is characterized by the longer
wavelengths of light, i.e., the lower frequency region. Similarly, "pink noise" has higher energy in the low
frequencies, hence the somewhat tongue-in-cheek term.
The Federal Standard 1037C Telecommunications: Glossary of Telecommunication Terms defines four
noise colors (white, pink, blue & black) and is considered the official source. No official standard could
be found for the others.
The following list of noise colors is loosely based on a rainbow-prism light analogy, where a prism
creates a rainbow effect by separating white light passed through it into a visible spectrum labeled red,
orange, yellow, green, blue, indigo, and violet from lowest to highest frequencies. Also shown is the
approximate slope of the power density spectrum relative to white noise used as the reference:
red noise also called brown noise: -6 dB/oct decreasing density (most amount of low frequency
energy or power; used in oceanography; power proportional to 1/frequency-squared); popcorn
pink noise: -3 dB/oct decreasing noise density (but, equal power per octave; 1/f noise or flicker
noise; power proportional to 1/frequency).
white noise: 0 dB/oct reference noise with equal power density (equal power per hertz; Johnson
blue (or azure) noise: +3 dB/oct increasing noise density (power proportional to frequency).
purple (or violet) noise: +6 dB/oct increasing noise density (power proportional to frequencysquared; most amount of high frequency energy or power).
black noise: silence (zero power density with a few random spikes allowed).
Other noise colors exist for specialized fields like video/photographic/image processing,
communications, mathematical chaos theory, etc., but are not found in pro audio circles.
Definitions for the noise colors orange, green, gray, and brown are found many times on
the Web, but all appear to be from the same document (whose true origin I could not
detect), e.g. see Bob Paddock at Circuit Cellar Online. Definitions without supporting
documentation are suspect.
noise criterion (NC) curves See NC curves
noise figure The ratio between the Johnson noise (or thermal noise) of the equivalent input resistance of a (4 of 8) [10/3/04 12:30:22 AM]
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circuit and its measured noise, expressed in decibels. It is the ratio of the output noise to the input noise,
so the answer is always positive, with a theoretically noise-free device having a noise figure of 0 dB.
noise floor Normally the lowest threshold of useful signal level, i.e., the residual noise with no signal
present (although sometimes audible signals below the noise floor can be recovered).
noise gate An expander with a fixed "infinite" downward expansion ratio. Used extensively for
controlling unwanted noise, such as preventing "open" microphones and "hot" instrument pick-ups from
introducing extraneous sounds into the system. When the incoming audio signal drops below the user setpoint (the threshold point) the expander prevents any further output by reducing the gain to "zero." The
actual gain reduction is typically on the order of -80 dB, thus once audio falls below the threshold,
effectively the output level becomes the residual noise of the gate. Common terminology refers to the gate
"opening" and "closing." Another popular application uses noise gates to enhance musical instrument
sounds, especially percussion instruments. Judicious setting of a noise gate's attack (turn-on) and release
(turn-off) times adds "punch," or "tightens" the percussive sound, making it more pronounced. A noise
gate is to an expander as a limiter is to a compressor. See RaneNote: The DC 24 Users Guide, RaneNote:
Signal Processing Fundamentals, and RaneNote: Good Dynamics Processing.
noise masking Acoustics. The practice of adding white noise to an audio system to make background
sounds unintelligible or less distracting; makes use of the human hearing masking phenomenon.
noise measurement filters See: weighting filters
noise reduction See: expander
noise shaping A technique used in oversampling low-bit converters and other quantizers to shift (shape)
the frequency range of quantizing error (noise and distortion). The output of a quantizer is fed back
through a filter, and summed with its input signal. Dither is sometimes used in the process. Oversampling
A/D converters shift much of it out of the audio range completely. In this case, the in-band noise is
decreased, which allows low-bit converters (such as delta-sigma) to equal or out-perform high-bit
converters (those greater than 16 bits). When oversampling is not involved, the noise still appears to
decrease by 12 dB or more because it is redistributed into less audible frequency areas. Further digital
processing usually reverses the benefits of this kind of noise shaping. See RaneNote: Digital Dharma of
Audio A/D Converters
NOM (number of open mics) An acronym believed first created in 1967, or 1968, by Bill Snow after he
retired from Bell Labs and went to work at Altec Lansing Research. It's use was popularized by Dan
Dugan, the father of the automatic microphone mixer and Altec Lansing, the manufacturer of his first
design. In Dan's original design, the automatic mic mixer, like human operators, turned the gain down on
unused mic channels and turned the gain up on active channels, all the while ensuring that the overall
level remained roughly constant. As a rough approximation, each doubling of the number of open mics (5 of 8) [10/3/04 12:30:22 AM]
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(NOM) cuts the gain by 3 dB, i.e., as more mics are opened up the mic mixer reduces overall gain. If not,
as mics open and close, the reverberation and ambient noise fluctuates unacceptably. NOM attenuation
techniques work to provide the gain, stability, and low noise qualities of a single open mic with the
benefits of multiple mics. [Historical Note: This concept was first written about by C.P. Boner & R.E.
Boner, in their paper "The Gain of a Sound System" April 1969, reproduced in Sound Reinforcement: An
Anthology (Audio Engineering Society, NY, 1978.]
nominal This word has several definitions but the one of importance to pro audio is its engineering sense
meaning: insignificantly small; trifling: a nominal amount. It does not mean average or typical as is so
often seen.
NOMM (number of open mics & mixers) A term created by Rane Corporation extending the concept of
NOM (above) to include multiple mixers as well as microphones. As used by Rane, it is NOM-like in that
feedback stability is maintained, however, since large systems have mics across multiple mixers, Rane
includes these mixers in the NOMM calculation. For example, in audio conferencing, when the chairman
is speaking and someone else quickly answers "yes," coughs, or drops a pen, most mic mixers running in
NOM mode are annoying because they reduce the level of the chairman mic just because someone else
made a noise. The Rane NOMM approach avoids this annoyance by keeping the chairman's mic at the
same gain while still allowing the interruption to be heard, yet at a reduced gain from its full gated level.
nonlinear Electronics. The amplitude of the output is not linearly proportional to the input. If a true sine
wave were transmitted through a nonlinear device, its shape would be changed. [IEEE] Contrast: linear.
nonvolatile Refers to a memory device that does not lose its data when power is removed from the
normaling jacks See patchbay
notch filter A special type of cut-only equalizer used to attenuate (only, no boosting provisions exist) a
narrow band of frequencies. Three controls: frequency, bandwidth and depth, determine the notch.
Simplified units provide only a frequency control, with bandwidth and depth fixed internally. Used most
often in acoustic feedback control to eliminate a small band of frequencies where the system wants to
howl (feedback).
NPO 1. Ceramic capacitors Temperature coefficient designator meaning negative-positive-zero, i.e., the
capacitance drifts negative and positive averaging zero. A marking meaning stable with temperature. 2.
Medicine Abbreviation for nil per os, or nothing by mouth.
NRE (non-recurring engineering charge) A one-time engineering charge for product development,
separate from royalty or licensing fees.
NSCA (National Systems Contractors Association) "Founded in 1980 as the National Sound Contractors (6 of 8) [10/3/04 12:30:22 AM]
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Association, the NSCA underwent a name change in 1994 to better reflect the diversification found within
the hi-tech industry of electronic systems. Rather than focusing solely on the installation of audio
systems, today's innovative member companies of the NSCA expanded into other fields, including audio,
video, intercom/paging, telecommunications, security/access control, and many others." [from NSCA
NSP (native signal processing) Intel-designed method of using a powerful microprocessor (like their
Pentium CPU) for signal processing functions normally done by separate DSP chips. Not finding many
NSSP (National Standards Systems Network) A Web-based service launched by ANSI, along with
government and industry partners. A full search & sales service provides for locating and buying virtually
any standard. More than 100,000 global standards are available. Over 25 standards groups provide
technical specs for this database, including ISO. The EIA endorsed the project.
NTMTM Crossover Filter (Neville Thiele MethodTM Crossover Filter) Trademarked term for the
patented technology developed by Neville Thiele for Whise Acoustics in Australia. Two choices are
offered, a 4th-order with rolloff slopes of 36 dB/octave and an 8th-order with 52 dB/octave slopes. The
published curves resemble 4th- and 8th-order cascaded elliptic filters.
NTSC (National Television Standards Committee) The United States and Japan standard for color
formatting for television transmission developed in the 1950s. Compare with PAL/SECAM.
null modem cable Special wiring of an RS-232 cable such that a computer can talk to another computer
without a modem (thus "null" modem). As a minimum, a null modem cable reverses pins 2 and 3 on a
standard RS-232 cable - but other pins may also need changing and shorting together.
numerator Mathematics. The top part of a common fraction.
numerological nonsense John Allen Paulos' wonderful page of rationality helping to fight off the
increasing numbers of irrational parents/teachers/politicians/scientists/engineers/audiophiles/(your
favorite here).
Nusselt number See: Grashof.
Nyquist frequency The highest frequency that may be accurately sampled. The Nyquist frequency is onehalf the sampling frequency. For example, the theoretical Nyquist frequency of a CD system is 22.05
kHz. See RaneNote: Digital Dharma of Audio A/D Converters
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Copyright Rane Corporation. All rights reserved. (8 of 8) [10/3/04 12:30:22 AM]
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Pro Audio Reference
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1/4" TRS or 1/4" TS See connectors.
100Base-T or 1000Base-T See: Ethernet
1/f noise See flicker noise
object-oriented or object-based programming (Abbreviated OOP) A software technique in which a
system program is expressed completely in terms of predefined things (objects), consisting of a set of
variables and operations which can be performed on them, and the connections between objects.
ocarinaMusical Instrument. A small terra-cotta or plastic wind instrument with finger holes, a
mouthpiece, and an elongated ovoid shape. Named after Italian oca, goose, from the fact that its
mouthpiece is shaped like a goose's beak. (AHD)
occlusion or occlusion effect Hearing. The phenomenon resulting from wearing solid earplugs, hearing
aids or some IEMs that makes the wearer's voice sound hollow and boomy to themselves, i.e., a voice-ina-barrel effect. The earplugs block the ear canal resulting in a sound similar to sticking a finger in each
ear and talking. This closure effect also produces louder sounds to the wearer since the ear canal
blockage allows additional sound pressure to build up (rather than escape out the open ear canal) and be
conducted to the inner ear. This is easily demonstrated by pronouncing and sustaining the word "fee,"
then sticking your fingers in your ears and notice how much louder it sounds (oh go ahead, no one is
octal A number system using the base-8, i.e., each digit can be any of 8 values, represented by the digits
0-7. A three-bit binary number (since 2E3 = 8) can also represent each octal digit.
octave 1. Audio. The interval between any two frequencies having a ratio of 2 to 1. 2. Music a. The
interval of eight diatonic degrees between two tones, one of which has twice as many vibrations per
second as the other. b. A tone that is eight full tones above or below another given tone. c. An organ stop
that produces tones an octave above those usually produced by the keys played. (AHD)
octothorpe The "#" symbol on the telephone keypad, also known as a pound sign, crosshatch, number
sign, sharp, hash, crunch, mesh, hex, flash, grid, pig-pen, gate, hak, oof, rake, fence, gate, grid, gridlet, (1 of 5) [10/3/04 12:30:26 AM]
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square, and widget mark. Click the link to read the history of this creative word.
oersted Abbr. Oe The unit of magnetic field strength (intensity) in the centimeter-gram-second
electromagnetic system, equal to the magnetic intensity one centimeter from a unit magnetic pole. (IEEE)
Named after Hans Christian Oersted (1777-1851), Danish physicist. (AHD)
off-axis response Any direction other than the on-axis response, i.e., the response measured along the
imaginary straight line drawn through the geometric center of an object. In pro audio most often used in
measurements of loudspeakers, microphones and humans.
Ogg Vorbis An open, royalty-free, pro audio encoding and streaming technology that competes with
AAC, TwinVQ and other schemes. The name "Ogg" comes from a video game and "Vorbis" from a
Terry Pratchett novel.
ohm Abbr. R, (Greek upper-case omega ). A unit of electrical resistance equal to that of a conductor in
which a current of one ampere is produced by a potential of one volt across its terminals. [After Georg
Simon Ohm.]
Ohm, Georg Simon (1789-1854) German physicist noted for his contributions to mathematics,
acoustics, and the measurement of electrical resistance. (AHD)
ohmage Misnomer. No such word. Bad, bad, super bad. Wrongfully used as a term for loudspeaker
resistance. The correct term is impedance -- learn it; use it.
OIART (Ontario Institute of Audio Recording Technology) This Canadian school offers a three-term,
forty-six week immersion course designed to prepare graduates for a career in the professional audio
recording and audio communications industry.
OLED (organic light emitting diode) A type of LED display made from organic polymers (think plastic
that glows) that provides a wide viewing angle and uses low power. OLED displays do not require a
backlight as do LCD screens. OLED screens can also be fabricated on plastic as well as glass substrates,
making them more flexible and durable. See OLED for details.
OL light See overload light
Olson, Harry Ferdinand, Ph.D. (1901-1982) American engineer who worked 40 years at RCA labs,
recognized and honored as a pioneer and leading authority in acoustics and electronic sound recording.
He was granted over 100 patents, along with many awards and medals for his contributions to the science
of sound. He authored more than 130 technical papers and wrote several textbooks still considered the
best of their genre. (2 of 5) [10/3/04 12:30:26 AM]
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omnidirectional microphone One with a response pattern that is as close to a perfect sphere as possible.
Receives sound from all directions equally well. Compare: unidirectional mic and cardiod microphone
on-axis response See: off-axis response.
one-bit data converter Loose reference to any of the various data conversion schemes (e.g., delta-sigma,
adaptive delta modulation, etc.) that use only one binary bit (i.e., levels 1 and 0) in the conversion and
storage process.
one-third octave 1. Term referring to frequencies spaced every one-third of an octave apart. One-third of
an octave represents a frequency 1.26-times above a reference, or 0.794-times below the same reference.
The math goes like this: 1/3-octave = 2E1/3 = 1.260; and the reciprocal, 1/1.260 = 0.794. Therefore, for
example, a frequency 1/3-octave above a 1 kHz reference equals 1.26 kHz (which is rounded-off to the
ANSI-ISO preferred frequency of "1.25 kHz" for equalizers and analyzers), while a frequency 1/3-octave
below 1 kHz equals 794 Hz (labeled "800 Hz"). Mathematically it is significant to note that, to a very
close degree, 2E1/3 equals 10E1/10 (1.2599 vs. 1.2589). This bit of natural niceness allows the same
frequency divisions to be used to divide and mark an octave into one-thirds and a decade into one-tenths.
2. Term used to express the bandwidth of equalizers and other filters that are 1/3-octave wide at their -3
dB (half-power) points. 3. Approximates the smallest region (bandwidth) humans reliably detect change.
See: critical bands. Compare with: third-octave
onomatopoetic The formation or use of words such as buzz, hiss, splash, sizzle or murmur that imitate
the sounds associated with the objects or actions they refer to. (AHD) See zaa zaa.
OOP See: object-oriented
op amp (operational amplifier) An analog integrated circuit device characterized as having two opposite
polarity inputs and one output, used as the basic building block in analog signal processing. See: vacuumtube op amps.
opera 1. A theatrical presentation in which a dramatic performance is set to music. (AHD) 2. "I do not
mind what language an opera is sung in so long as it is a language I don't understand." Edward Appleton,
Observer August 28, 1955. (Crystal) 3. "An unalterable and unquestioned law of the musical world
required that the German text of French operas sung by Swedish artists should be translated into Italian
for the clearer understanding of the English-speaking audiences." Edith Wharton, 1920, The Age of
Innocence. (Crystal)
optical-fiber cable See fiber-optics.
optocoupler Any device that functions as an electrical-to-optical or optical-to-electrical transducer. (3 of 5) [10/3/04 12:30:26 AM]
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orange One of the words in the English language without a rhyme -- some others are "month," "purple,"
and "silver."
orange noise See noise color
ordinate Mathematics. The plane Cartesian coordinate representing the distance from a specified point to
the x-axis, measured parallel to the y-axis. (AHD)
organic LED See OLED
oronyms Speech. Streams of sound than can be carved into words in two different ways, i.e., it
illustrates the seamlessness of speech. For example oronyms are often found in songs and nursery rhymes
such as the famous "Mairzey doats and dozey doats, And little lamsey divey, A kiddley-divey do, Wouldn't
you?" From Pinker.
ORTF (Office de Radiodiffusion -- Television Francaise) An initialism formed from the name of the
French national broadcasting system, who designed a stereo microphone recording technique known as
the ORTF method. The technique uses two cardioid microphones with a spacing of 17 cm between the
microphone diaphragms, and with an 110° angle between the capsules. This technique reproduces stereo
cues similar to those used by the human ear to perceive directional information in the horizontal plane.
The spacing of the microphones emulates the distance between the human ears, and the angle between
the two directional microphones emulates the shadow effect of the human head. The ORTF stereo
technique provides the recording with a wider stereo image than X-Y stereo while still preserving good
mono information.
oscillator Electronics & Synthesizers. A circuit that continuously alternates between two (or more) states
(IEEE); the period between alternations defines the frequency of oscillation. A common said complaint
of electronic engineering students is that they build "amplifiers that oscillate and oscillators that
OSD (on-screen display) chip An integrated circuit providing all necessary functions for adding text to
television or video monitor display screens.
OSI (open system interconnection) The only internationally accepted framework of standards for
communication between different systems made by different vendors. The model originally developed by
ISO describing computer communication services and protocols without making assumptions concerning
language, operating systems or application issues. The main goal is to create an open systems networking
environment where any vendor's computer system, connected to any network, can freely share data with
any other computer system on that network See: The 7 Layers of the OSI Model
OTPROM (one-time programmable read-only memory) A redundant term, incorrectly used to mean (4 of 5) [10/3/04 12:30:26 AM]
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PROM - a PROM, by definition, is a one-time device.
outboard unit External, usually referring to a separate piece of signal processing gear located remote to
a mixer that connects in the effects loop.
out-of-phase In an un-synchronized or un-correlated way. See polarity and phase et al.
overload light or OL light An indicator found on pro audio signal processing units that lights once the
signal level exceeds a preset point. There is no standard specifying when an OL light should illuminate,
although common practice makes it 3-4 dB below actual clipping. Good signal processing design ensures
that the OL light illuminates anytime the signal exceeds the set point, anywhere in the signal path, not
just the input or output level.
overs A term associated with A/D converters used to describe input signals exceeding the full scale range
(0 dBFS). Overs indicators vary from simple single LEDs to elaborate calibrated digital meters. To be of
genuine value the overs indicator, however displayed, must be based on reading the true digital code
associated with the input level. It is important to distinguish between 0 dBFS and overs; they are not the
same. 0 dBFS is the absolute highest voltage level that any particular A/D can convert. It produces the
equivalent of a digital code consisting of all 1s. No digital level can exceed 0 dBFS. A 0 dBFS voltage
level and all levels greater than this produce the same output code of all 1s. A true overs indicator
actually counts the number of times that the 0 dBFS level was exceeded and displays this number. As yet
there is no standard as to how many samples exceeding 0 dBFS constitutes an over. Everyone agrees that
very brief excursions beyond 0 dBFS (producing digital clipping) cannot be heard; however no such
agreement exists as to just how many samples it takes before an over is audible.
oversampling 1. Sampling at a rate higher than the sampling Nyquist theorem. 2. A technique where
each sample from the data converter is sampled more than once, i.e., oversampled. This multiplication of
samples permits digital filtering of the signal, thus reducing the need for sharp analog filters to control
aliasing. See RaneNote: Digital Dharma of Audio A/D Converters
overtone Same as harmonic.
Oz From Frank Baum's "The Wizard of Oz," the name was created when he looked at his filing cabinet
and saw "A-N," and "O-Z," hence "Oz."
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Further study: Perfect-Q
P2C2E (process too complex to explain) [Thanks, Lou!]
P2P See peer-to-peer
p's and q's From old British saying: pints and quarts [... and you know pints and quarts of what.] 1.
Socially correct behavior; manners. 2. The way one acts; conduct: was told to watch his p's and q's or he
would be fired. (AHD)
P.A. (public address) See Bruce Borgerson excellent S&VC article on P.A. vs. SR.
PA-232 An RS-232-based variant of the PA-422 AES standard.
PA-422 A pro audio implementation of Electronics Industries Association EIA-422 interconnection
standard, defined and adopted by the Audio Engineering Society as AES Recommended practice for
sound-reinforcement systems - Communications interface (PA-422) AES 15-1991 (ANSI S4.49-1991).
pad See attenuator pad.
PAL® (programmable array logic) Original registered trademark of Monolithic Memories Inc. (now
owned by Advanced Micro Devices, Inc.) for their fuse-link once-programmable logic parts that have a
programmable AND array, but a predefined OR array. See also: PLA, PLD & FPGA.
PAL/SECAM (phase alternated line/sequential couleur avec memoire or sequential color with
memory) The European and Australian standard for color formatting for television transmission
developed in the 1960s and used most everywhere in the world except the U.S.A. and Japan, which use
PAMA (Professional Audio Manufacturers Alliance) The voice of the professional audio
manufacturing community. (1 of 18) [10/3/04 12:30:40 AM]
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pan (panoramic) control A control found on mixers, used to "move," or pan the apparent position of a
single sound channel between two outputs, usually "left," and "right," for stereo outputs. At one extreme
of travel the sound source is heard from only one output; at the other extreme it is heard from the other
output. In the middle, the sound is heard equally from each output, but is reduced in level by 3 dB relative
to its original value. This guarantees that as the sound is panned from one side to the other, it maintains
equal loudness (power) for all positions. Contrast with balance and crossfade controls.
pandemonium Loud, confused, or disagreeable sound implying disorderly tumult together with loud,
bewildering sound. [AHD]
PAQRAT® A registered trademark of Rane Corporation for their recording converter devices, RC 24T
& RC 24A, that convert AES/EBU stereo 18-24 bit digital audio two track data into 16-bit compatible
four tracks for recording and playback on 1st-generation 16-bit modular digital multitrack tape machines
such as Alesis ADAT and Tascam DTRS (DA-88) models.
paragraphic See: parametric equalizer
parallel interface The printer port in the PC world. A parallel port conforming to the quasi-standard
called the Centronics Parallel Standard (there is no EIA standard). Originally a 36-pin connector, now
more often a D-25 type connector. A parallel (as opposed to serial) interface transfers all bits in a word
simultaneously. See also: serial interface.
parametric equalizer First named by George Massenburg, a multi-band variable equalizer offering
control of all the "parameters" of the internal bandpass filter sections. These parameters being amplitude,
center frequency and bandwidth. This allows the user not only to control the amplitude of each band, but
also to shift the center frequency and to widen or narrow the affected area. Available with rotary and slide
controls. Subcategories of parametric equalizers exist which allow control of center frequency but not
bandwidth. For rotary control units the most used term is quasi-parametric. For units with slide controls
the popular term is paragraphic. The frequency control may be continuously variable or switch selectable
in steps. Cut-only parametric equalizers (with adjustable bandwidth or not) are called notch equalizers, or
band-reject equalizers. See RaneNote: Constant-Q Graphic Equalizers.
parity A redundant error detection method in which the total number of binary 1's (or 0's) is always made
even or odd by appending one or more bits.
partial or partial tone See: harmonic
pascal Abbr. Pa. The International System unit of pressure equal to one newton per square meter. [After
Blaise Pascal.]
Pascal, Blaise (1623-1662) French philosopher and mathematician. Among his achievements are the (2 of 18) [10/3/04 12:30:40 AM]
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invention of an adding machine and the development of the modern theory of probability.
passband The range of frequencies passed by an audio low-pass, high-pass or bandpass filter. Normally
measured at the -3 dB point: the frequency point where the amplitude response is attenuated 3 dB
(decibels) relative to the level of the main passband. For a bandpass filter two points are referenced: the
upper and lower -3 dB points. The -3 dB point represents the frequency where the output power has been
reduced by one-half. [Technical details: -3 dB represents a multiplier of 0.707. If the voltage is reduced
by 0.707, the current is also reduced by 0.707 (ohms law), and since power equals voltage-times-current,
0.707 times 0.707 equals 0.5, or half-power.] The opposite of stopband.
passive crossover A loudspeaker crossover not requiring a power supply for operation. Normally built
into the loudspeaker cabinet. Passive crossovers do not require separate power amplifiers for each driver.
See: active crossover See RaneNote: Signal Processing Fundamentals.
passive equalizer A variable equalizer requiring no power supply to operate. Consisting only of passive
components (inductors, capacitors and resistors) passive equalizers have no AC line cord. Favored for
their low noise performance (no active components to generate noise), high dynamic range (no active
power supplies to limit voltage swing), extremely good reliability (passive components rarely break), and
lack of RFI interference (no semiconductors to detect radio frequencies). Disliked for their cost (inductors
are expensive), size (and bulky), weight (and heavy), hum susceptibility (and need careful shielding), and
signal loss characteristic (passive equalizers always reduce the signal). Also inductors saturate easily with
large low frequency signals, causing distortion. Rarely seen today, but historically they were used
primarily for notching in permanent sound systems. See RaneNote: Operator Adjustable Equalizers.
PASTI (public address speech transmission index) Chiefly British term for STIPa.
patchbay or patch panel A flat panel, or enclosure, usually rack-mounted, that contains at least two rows
of 1/4" TRS connectors used to "patch in" or insert into the signal path a piece of external equipment
(really dense configurations use 4.4 mm miniature or "bantam" jacks). The two rows consists of "send"
(top row) and "receive" (bottom row) jacks wired for true balanced interconnection, i.e., tip = positive
signal, ring = negative signal, sleeve = shield ground (unbalanced patchbays exist but should not so no
further discussion). The two rows are tied together by shorting contacts such that the normal operation
(hence, "normaling" jacks) is to short the send and receive tip-to-tip & ring-to-ring (the sleeves are
always connected) maintaining the signal path until something is plugged in (or jacked in as cyberpunks
love to say). Popular in recording studios where it is common to change the units in the signal path for
each new session or client.
patents See USPTO
PBX (private branch exchange) Term referring to hardware allowing several telephones to be connected
to a smaller number of lines. (3 of 18) [10/3/04 12:30:40 AM]
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PC (personal computer) Original term coined by IBM to describe their first personal computers; now
used to mean all IBM-compatible personal computers, or any personal computer.
PC-DOS® (personal computer disk operating system) IBM's trademarked acronym for their PC
operating system. If PC-DOS runs on an IBM compatible, it is then called MS-DOS.
PCI (peripheral component interconnect) Intel-designed high performance CPU interconnect strategy
for "glueless" I/O subsystems. A 32- or 64-bit local-bus specification, characterized by being selfconfiguring, open, high-bandwidth and processor-independent - allowing for modular hardware design.
PCM (pulse code modulation) A conversion method in which digital words in a bit stream represent
samples of analog information. The basis of most digital audio systems, first invented by Alec H. Reeves
in 1937 [see The Digital Revolution]. Also see RaneNote: Digital Dharma of Audio A/D Converters
PCMCIA (Personal Computer Memory Card International Association) 1. The association and first
name given to the standardized credit-card size packages (aka smart cards) for memory and I/O
(modems, LAN cards, etc.) for computers, laptops, palmtops, etc. Nicknamed PC-Card, which is now the
preferred term. 2. Popularly believed to stand for People Can't Memorize Computer Interface Acronyms.
PDA (personal digital assistant) A small palmtop-like computer designed for specific tasks such as a
pocket calculator. Other examples include personal electronic diaries, memo takers, communicators, web
browsers, dictionary-translators, etc. Apple's Newton is a PDA. IBM named theirs personal
pdf (probability density function) See probability density function
PDF files (portable document format) Suffix letters used (.pdf) to indicate an Adobe Acrobat document.
peaking response Term used to describe a bandpass shape when applied to program equalization.
peak program meter See: PPM
PEAQ (perceptual evaluation of audio quality) Term for the ITU-R recommendations for the objective
measurement of perceived audio quality for perceptually coded digital audio signals. Popularly called the
new "electronic ear" to provide yardstick values for digitally coded audio quality, there are a series of
recommendations covering various aspects of this method (e.g., ITU-R Rec. BS.1387, ITU-R Rec.
BS.1116 and ITU-R Rec. BS.562-3). For details of this complex issue see the definitive overview paper
by Thiede, et al., "PEAQ -- The ITU Standard for Objective Measurement of Perceived Audio Quality," (4 of 18) [10/3/04 12:30:40 AM]
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J. Audio Eng. Soc., vol. 48 (Audio Engineering Society, January/February 2000). See also CRC's
(Communication Research Centre) excellent summary with the same title.
PEC (parallel earth conductor) Modern best practices for EMC in installations (per IEC 61000-52:1998) require the use of trays, conduits and heavy-gauge earth conductors, known as "parallel earth
conductors" (PEC) to divert power currents away from cables and their shields. See Williams' EMC for
Systems and Installations for full details
PEC (protective earth conductor) Conductor to be connected between the protective earth terminal and
an external protective earthing system.
peer-to-peer abbreviated P2P A network term popularly used to mean an equal access network where
every node can send/receive data at any time without waiting for permission, i.e., each node can act as a
client or server. An example would be a group of computers that communicate directly with each other,
rather than through a central server.
Percentage Articulation Loss of Consonants (%ALCONS) A term first published in the paper by V.
M. A. Peutz. "Articulation Loss of Consonants as a Criteria for Speech Transmission in a Room," J.
Audio Eng. Soc., Vol. 19, Dec 1971. It is a measure of room speech intelligibility based on the measured
RT60 time and dimensions of the room, combined and expressed as a percent, where 0% (no loss of
consonants) is perfect, 10% is poor, and 15% is intolerable. Popularized by Syn-Aud-Con's Pat Brown
who teaches how to use it to direct loudspeaker line arrays. See Peter Mapp's excellent AES preprint 5668
presented at the 113th Convention of the Audio Engineering Society, Los Angeles, October 2002.
Contrast with STI and RASTI.
perceptual coding A lossy digital audio data compression technique based on the human hearing
mechanisms of masking and critical bands. AC-3 and AAC are examples of digital audio data
compression schemes based on perceptual coding.
Perfect-QTM graphic equalizer Rane Corporation's trademark term for their true response graphic
equalizer technology. See: RaneNote: Perfect-Q, the Next Step in Graphic Equalizers
period Abbr. T, t 1. The period of a periodic function is the smallest time interval over which the
function repeats itself. [For example, the period of a sine wave is the amount of time, T, it takes for the
waveform to pass through 360 degrees. Also, it is the reciprocal of the frequency itself: i.e., T = 1/f.] 2.
Mathematics. a. The least interval in the range of the independent variable of a periodic function of a real
variable in which all possible values of the dependent variable are assumed. b. A group of digits separated
by commas in a written number. c. The number of digits that repeat in a repeating decimal. For example,
1/7 = 0.142857142857... has a six-digit period. (AHD)
periodic motion Motion that repeats itself at regular or predictable intervals. (5 of 18) [10/3/04 12:30:40 AM]
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peripheral Equipment physically independent of, but which may interface to a computer or a controller.
Perkins EQTM Trademark of Mackie for their new mixing board EQ designed by the legendary Cal
Perkins of Marantz, JBL & Fender fame..
personal monitors See: IEM.
PET (protective earth terminal) Terminal connected to conductive parts of Class I equipment for safety
purposes. This terminal is intended to be connected to an external earthing system by a PEC (protective
earth conductor) .
PFC (power-factor-corrected) See power-factor-corrected.
PFL (pre-fade listen) A term used on recording consoles and mixers, referring to a signal taken before
the main channel fader. The significance is this signal is not affected by the fader position. Normally used
to monitor (via headphones) to an individual input (or a small group of inputs) without affecting the main
outputs, particularly useful in that it allows listening to an input with its fader all the way down (off). In
broadcast this function is often called cueing, while recording or live-sound users may also refer to it as
soloing. Compare: AFL and APL.
phantom power The term given to the standardized scheme of providing power supply voltage to certain
microphones using the same two lines as the balanced audio path. The international standard is IEC
60268-15, derived from the original German standard DIN 45 596. It specifies three DC voltage levels of
48 volts, 24 volts and 12 volts, delivered through 6.8 k ohms, 1.2 k ohms, and 680 ohms matched
resistors respectively, capable of delivering 10-15 ma. The design calls for both signal conductors to have
the same DC potential. This allows the use of microphone connections either for microphones without
built-in preamps, such as dynamic types, or for microphones with built-in preamps such as condenser and
electret types.
[Phantom Power Mini-tutorial: Much confusion surrounds phantom power. This is an area where you
need to make informed decisions: Is it provided? Do you need it? Is it the correct voltage, and does it
source enough current for your microphone? There is a huge myth circulating that microphones sound
better running from 48 volts, as opposed to, say, 12 volts, or that you can increase the dynamic range of a
microphone by using higher phantom power. For the overwhelming majority of microphones both of
these beliefs are false. Most condenser microphones require phantom power in the range of 12-48 VDC,
with many extending the range to 9-52 VDC, leaving only a very few that actually require just 48 VDC.
The reason is that internally most designs use some form of current source to drive a low voltage zener
(usually 5 volts; sometimes higher) which determines the polarization voltage and powers the electronics.
The significance is that neither runs off the raw phantom power, they both are powered from a fixed and
regulated low voltage source inside the mic. Increasing the phantom power voltage is never seen by the
microphone element or electronics, it only increases the voltage across the current source. But there are (6 of 18) [10/3/04 12:30:40 AM]
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exceptions, so check the manufacturer, and don't make assumptions based on hearsay. From RaneNote:
Selecting Mic Preamps.]
phase Audio signals are complex AC (alternating current) periodic phenomena expressed mathematically
as phasors, or vectors. Phase refers to a particular value of t (time) for any periodic function, i.e. it is the
relationship between a reference point and the fractional part of the period through which the signal has
advanced relative to an arbitrary origin. [The origin is usually taken at the last previous passage through
zero from the negative to the positive direction -- IEEE.] See Georgia State University's great website
HyperPhysics for more detail.
phase cancellation When two signals have the same exact time relationship to each other, they are said
to be "in-phase;" if they do not, they are said to be "out-of-phase." (Compare with polarity) If two out-ofphase signals add together, since this is vector arithmetic (see phasor), they will, in fact, subtract from one
another. This is called phase cancellation. Another type of phase cancellation occurs when water waves
interact. One wave's energy becomes stronger when two waves collide in-phase (summing) and becomes
weaker when they collide out-of-phase (cancelling).
phase delay A phase-shifted sine wave appears displaced in time from the input waveform. This
displacement is called phase delay and is usually constant for all frequencies of interest. Used as another
name for group delay; however there are instances where they are not the same, for example systems
exhibiting ripple in their phase vs. frequency characteristics.
phase lag and phase lead Phase shift caused by reactive elements (capacitors and inductors) that either
subtracts (lag) or adds (lead) degrees of shift. See RaneNote: Linkwitz-Riley Crossovers up to 8th-Order:
An Overview.
phase linear 1. Chiefly a European phrase meaning "linear phase." Any system which accurately
preserves phase relationships between frequencies, i.e., that exhibits pure delay. See: group delay. 2.
Consumer hi-fi company where all five Rane owners worked before starting Rane Corporation. See Phase
Linear History/Repair.
phase lock loop A circuit for synchronizing a variable local oscillator with the phase of a transmitted
signal. The circuit acts as a phase detector by comparing the frequency of a known oscillator with an
incoming signal and then feeds back the output of the detector to keep the oscillator in phase with the
incoming frequency. Commonly used for bit-synchronization.
phaser Also called a "phase shifter," this is an electronic device creating an effect similar to flanging, but
not as pronounced. Based on phase shift (frequency dependent), rather than true signal delay (frequency
independent), the phaser is much easier and cheaper to construct. Using a relatively simple narrow notch
filter (all-pass filters also were used) and sweeping it up and down through some frequency range, then
summing this output with the original input, creates the desired effect. Narrow notch filters are (7 of 18) [10/3/04 12:30:40 AM]
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characterized by having sudden and extreme phase shifts just before and just after the deep notch. This
generates the needed phase shifts for the ever-changing magnitude cancellations.
phase shift The fraction of a complete cycle elapsed as measured from a specified reference point and
expressed as an angle. See RaneNote: Exposing Equalizer Mythology.
phasor 1. A complex number expressing the magnitude and phase of a time-varying quantity. It is math
shorthand for complex numbers. Unless otherwise specified, it is used only within the context of steadystate alternating linear systems. [Example: 1.5 /27° is a phasor representing a vector with a magnitude of
1.5 and a phase angle of 27 degrees.] 2. For some unknown reason, used a lot by Star Fleet personnel.
phat adj. Slang phatter, phattest Excellent; first-rate: phat fashion; a phat rapper. [Earlier, sexy (said of
a woman), of unknown origin.] (AHD)
phi Mathematics. The symbol for the "Golden Rectangle" or "Golden Ratio." It is a never-ending, neverrepeating number found by calculating this formula:
See Livio for all the fascinating details of this most intriguing
phlogiston A hypothetical substance formerly thought to be a volatile constituent of all combustible
substances released as flame in combustion. (AHD) See: smoke
Phoenix-blocks (or -connectors or -strips) A term, becoming generic, meaning disconnectable, or
pluggable terminal blocks, after Phoenix Contact connector company, although dozens of companies
make them. Also called Euroblocks. See connectors.
phon A unit of apparent loudness, equal in number to the intensity in decibels of a 1,000 Hz tone judged
to be as loud as the sound being measured.
phone jack Same as ¼" TRS, see connectors.
phonograph 1. Literally means "writing sound", a term coined from Greek roots. 2. A machine that
reproduces sound by means of a stylus in contact with a grooved rotating disk. (AHD) 3. "An irritating
toy that restores life to dead noises." -- Ambrose Bierce.
phonograph cartridge See: pickup
phono jack Same as RCA, see connectors. (8 of 18) [10/3/04 12:30:40 AM]
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physics Some claim that studying physics is all you need for a complete education -- after a visit to
HyperPhysics you may agree.
pi Symbol (Greek lower-case pi) 1. Mathematics. A transcendental number, approximately 3.14159,
represented by the Greek lower-case pi symbol, that expresses the ratio of the circumference to the
diameter of a circle and appears as a constant in many mathematical expressions. (AHD) 2. Filters. Equal
to 180 degrees or integral multiples thereof. See Beckmann
PI 14 See: Pseudoacoustic Infector
picket fencing See: multipath.
pickup Transducers. A device that "picks up" sound and converts it into an electrical signal. Many
technologies exist, from the most popular electromagnetic models (magnetic pickups) found on electric
guitars to piezoelectric models seen on acoustic instruments and used in early phonograph cartridges
(soon replaced with electromagnetic models using either moving magnet or moving coil technologies).
pico- Prefix for one trillionth (10E-12), abbreviated p.
PICO (Program In, Chip Out) Hewlett-Packard technology that use computers to design computers.
piezo Transducers. Greek, to press tight, squeeze. Shortened form for piezoelectric, the name given to a
class of materials (dielectric crystals) that produce electricity or become polarized when mechanically
strained or stressed. In pro audio used to create pickups, microphones and loudspeakers or buzzers, and in
digital circuits quartz crystals for stable timing references.
pin-1 problem Phrase created by Neil A. Muncy (Canadian electroacoustic system consultant; also see:
PSW Live Chat With Neil Muncy) to describe the improper connection of the "pin-1" terminal of XLR
connectors found on analog pro audio equipment. The correct way to terminate pin-1 of XLR connectors
is to bond it to the chassis immediately at the entry and exit points. It should not be connected to circuit
signal ground. Equipment with pin-1 left open, or connected to circuit signal ground is said to suffer from
a "pin-1 problem." See Steve Macatee's Considerations in Grounding and Shielding , RaneNote: Sound
System Interconnection, Philip Giddings' "A New and Important Audio Equipment Evaluation Criteria,"
and Tony Waldron and Keith Armstrong, "Bonding Cable Shields at Both Ends to Reduce Noise," EMC
Compliance Journal, May 2002.
pin jack Same as RCA, see connectors.
pink noise Pink noise is a random noise source characterized by a flat amplitude response per octave (9 of 18) [10/3/04 12:30:40 AM]
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band of frequency (or any constant percentage bandwidth), i.e., it has equal energy, or constant power,
per octave. Passing white noise through a filter having a 3 dB/octave roll-off rate creates pink noise. See
white noise discussion for details. Due to this roll-off, pink noise sounds less bright and richer in low
frequencies than white noise. Since pink noise has the same energy in each 1/3-octave band, it is the
preferred sound source for many acoustical measurements due to the critical band concept of human
hearing. The name comes from the filtering of white noise. White noise is analogous to white light in that
it contains all audible frequencies distributed uniformly throughout the spectrum. Passing white light
through a prism (a form of filter) breaks it down into a range of colors. Examination shows that red light
is characterized by the longer wavelengths of light, i.e., light in the lower frequency region. Similarly,
pink noise has higher energy in the low frequencies, hence the somewhat tongue-in-cheek term pink. See
noise color.
pinna Hearing. The outer portion of the ear; acts like an audio filter or equalizer and separates sounds
coming from the front and rear. Also called auricle.
pipe Saxophone. (Decharne)
pitch Frequency or tone of a sound.
pitch-shifting or pitch-transposing Recording. An effect that changes the pitch (frequency or tone) of
musical notes without changing their length, or timing. For example, fast-forwarding an audio cassette
results in a higher pitched version of the music at an increased pace. Pitch-shifting does the same thing
without changing the music speed. One way to accomplish this is to use continuous wavelet transform,
where the musical signal is decomposed into separate wavelets and processed. First, the pitch is modified
by a constant related to the required pitch change, then the time scale is adjusted appropriately.
pivot and jewel Electrical meter mechanism. Consisting of a hardened pivot between two polished
bearing surfaces.
Favored for rugged and shock resistant applications such as industrial and marine.
pixel (picture element) The smallest element on a display surface, like a video screen, that can be
assigned independent characteristics.
PLA (programmable logic array) A programmable logic device in which both the AND & OR arrays are
placement equalization or placement EQ Term coined by Tomlinson Holman (of THX fame) to mean
moving around the loudspeaker and listener until the room response (at the listener) is smoothest.
PLD (programmable logic device) The generic name for an integrated circuit offering a vast array of
logic function building blocks that the circuit designer defines (programs) to interconnect for specific (10 of 18) [10/3/04 12:30:40 AM]
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plenum 1. A ductwork system in which air is at a pressure greater than that of the outside atmosphere. 2.
Such a system located in the space above a suspended ceiling, used to circulate air back to a building's
plenum cable The type of cable used when smoke retardant properties are required. Plenum cable is
specifically designed for use in a plenum area (see above) which is typically used as the distribution
system in buildings. Most cities requiring all cable ran through a plenum ceiling to be plenum cable
which has insulated conductors jacketed with PVDF (polyvinylidene difloride) -- a material providing low
flame spread and low smoke producing properties. Underwriters Laboratories approved plenum cables for
non-conduit applications located in environmental air spaces. This low cost alternative has replaced
traditional conduit use in many commercial installations.
plug See: jacks and plugs
plumbing Trumpet. (Decharne)
PM (personal monitors) See: IEM.
PMPO (peak music power output or peak momentary performance output) An arbitrary made-up
specification (marketing gimmick) that supposedly measures the total maximum power output from an
amplifier at a given THD+N level during a brief transient. Also used to express dubious loudspeaker
power ratings. Typically there is a 12-to-1 difference between PMPO and real apparent power (67:1 is the
PnP (plug 'n play) 1. Computers. The technology that lets certain operation systems (Windows 95,
others) automatically detect and configure most of the adapters and peripherals connected to or sitting
inside a PC. 2. Any system with automatic detection and configuration of auxiliary devices.
PoE (Power over Ethernet) The name for the technology defined by IEEE 802.3af that allows Ethernet
appliances to receive power as well as data over existing LAN CAT 5 cabling.
polarity A signal's electromechanical potential with respect to a reference potential. For example, if a
loudspeaker cone moves forward when a positive voltage is applied between its red and black terminals,
then it is said to have a positive polarity. A microphone has positive polarity if a positive pressure on its
diaphragm results in a positive output voltage. [Usage Note: polarity vs. phase shift: polarity refers to a
signal's reference NOT to its phase shift. Being 180° out-of-phase and having inverse polarity are
DIFFERENT things. We wrongly say something is out-of-phase when we mean it is inverted. One takes
time; the other does not.] (11 of 18) [10/3/04 12:30:40 AM]
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poles Mathematics. The roots of the denominator of a circuit transfer function, i.e., the values that make
the denominator equal zero. Compare with zeros.
Pooh "I am a bear of very little brain, and long words bother me." A.A. Milne, Winnie-the-Pooh, Ch. 4.
popcorn noise Solid-state physics. Noise primarily found in integrated circuit audio amplifiers that
exhibit a sizzling, frying hot-grease kind of sound, similar to popcorn popping. Found to be due to
manufacturing defects in the form of metallic impurities in the junctions, often caused by dirty fabrication
lines. The frequency spectrum typically conforms to 1/frequency-squared. See red/brown noise under
noise color.
pop filter or popshield Microphones. A filter, usually made of acoustic foam material, put over a
microphone to reduce wind noises and "pop" sounds from users.
portmanteau word A word formed by merging the sounds and meanings of two different words, as
chortle, from chuckle and snort, or motel, from motor and hotel. (AHD) Compare with acronym
post-echo See: print-through
pot (lowercase) Shorten form of potentiometer (and if you think I'm gonna make some cheap joke about
the smokin' kind, you're crazy).
potentiometer A three-terminal variable resistor. Two terminals connect to the ends of the resistor, while
the third terminal is attached to a movable device that makes contact with the resistive element. The
movable terminal, or slider, is capable of being positioned from one end of the element to the other.
Many physical arrangements exist, with the rotary design being the most common, followed by linear
motion (used in graphic equalizers, for example), all the way to tiny SMT devices. Often used as voltage
dividers in electronic circuits, the input voltage is applied to the top of the resistive element, while the
other end is tied to ground or a common reference and the output is taken from the slider. When the slider
is positioned to the top extreme, the output equals the input, or the entire voltage; moving it to the bottom
extreme gives an output of zero volts; and every possible level between is available as the slider is moved
from one end to the other. The most common application uses this arrangement to control the volume of
an audio device. In this manner the voltage, or electrical potential is varied, hence, a potentiometer. The
taper of the pot controls the rate at which the voltage changes as the slider is moved. The taper defines
the amount of resistive change as a function of travel. Several popular examples follow:
audio taper (aka A-taper): Usually 15% resistance at the 50% rotation point
linear taper (aka B-taper): Always 50% resistance at the 50% travel point
log taper Often used as an audio taper since its 50% rotation point has 10%
resistance (12 of 18) [10/3/04 12:30:40 AM]
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MN taper (aka balance pot) Special taper developed for home stereo "Balance" controls. Consists of two
sections (one for each channel) operating opposite each other. Exactly one-half of each section is a zero
resistance surface (i.e., solid-copper or equivalent), the next 50% of travel is linear taper. Therefore for
one channel rotating the slider through the first 50% of travel does not change the level at all, while the
other channel is reduce from full to zero, and vice versa, with the middle position (usually featuring a
center-detent) always passing full signal to each channel. See balance control
POTS (uppercase) Acronym for plain old telephone system. The normal single line basic telephone
service. Often used in reference to modems associated with regular telephone lines. See RaneNote:
Interfacing Audio and POTS.
power 1. Electricity a. The product of applied voltage (potential difference) and current in a directcurrent circuit (or the voltage squared divided by the resistance, or the current squared times the
resistance). b. The product of the effective values of the voltage and current with the cosine of the phase
angle (between current and voltage) in an alternating-current circuit. See: apparent power and rms power
2. Physics The rate at which work is done, expressed as the amount of work per unit time, and measured
in units such as the watt (1 joule per second, which equals the power dissipated (as heat) by 1 ohm of
resistance when 1 ampere of current passes through it) and horsepower (equal to 745.7 watts). (AHD)
power amplifier See amplifier
power amplifier dummy load See amplifier dummy load
power factor Abbr. PF Electronics. The ratio of the total (or real) power in watts (resistive load) to the
total apparent power in voltamperes (VA) (reactive load). The difference between watts and VA is due to
reactive load impedance. Apparent power equals watts only for a purely resistive load (i.e., zero degrees
phase shift between the applied voltage and the resultant current). Power factor is best thought of
intuitively as the multiplier (ranging between 0 and 1) that you must use to obtain the real power from the
apparent power. For example if you measure the rms voltage and current of a circuit and multiply them
together you obtain the apparent power, but you must multiply this value by the power factor to obtain
the real power. If the load is purely resistive then the phase difference between the voltage and current
will be zero and the power factor will be one, and the apparent power will equal the true power -- but
only for a resistive load. For a reactive load (any load with inductive and/or capacitive reactance, i.e., any
real load) there will be a phase difference between the voltage and the current due to the phase delay
introduced by the reactive elements. Simply put, since the maximum voltage and current do not occur at
the same instant of time the amount of power developed is less than the measured rms voltage and current
multiplied together.
Since power factor is a ratio, and hence unitless, it can be expressed in several ways -- all of them equal.
It is the ratio of watts to voltamperes, of resistance to reactance, and if the phase shift in degrees is known
(phase angle), it is the cosine of that angle, or cos. If the angle is zero the PF = 1, and if the angle is 90° (13 of 18) [10/3/04 12:30:40 AM]
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the PF = 0.
power-factor-corrected (PFC) 1. General. Power factor correction reduces phase error and improves
wave shape in electrical sources and power supplies. The PFC circuitry acts to make the load appear more
resistive. Power factor varies between zero and one in value. It is unity, or one, when it is purely restive.
This is when the input current wave shape and phase exactly match the input voltage wave shape and
phase. AC mains voltage is supposed to be sinusoidal, so a power factor of unity requires in-phase,
sinusoidal current. Power factor correction is any passive or active measure taken to improve the phase
relationship and/or harmonic content (shape) of current so that it matches the input voltage. 2. Passive.
Any system that has a passive power-factor-correcting device, such as an inductor or capacitor, installed
to reduce the phase difference between the rms voltage and rms current. For example, adding series
inductance to reduce the phase lead between voltage and current seen with standard rectifier/capacitor
power supplies. 3. Active. Any system using active circuit elements such as switching transistors, in
conjunction with reactive components, to improve power factor. The switching elements operate at
relatively high frequencies, allowing smaller reactive components (than required by passive methods) to
produce the desired results. The majority of active PFC circuits work to insure that mains currents will
flow, even when instantaneous line voltage is low. Very high power factor values are obtained by actively
controlling instantaneous line current so that it remains proportional to the average power demanded by
the load.
[PFC Mini-tutorial: Real power, i.e., purely resistive load, is measured in watts and gets converted to
audio power (to drive loudspeakers, for instance). Apparent power is measured in volt-amperes and is
what blows circuit breakers. This is because circuit breakers only measure current. As power factor gets
worse circuit breaker ratings must go up to prevent tripped breakers. A power-factor-corrected system
allows full power out of each branch circuit. Electronic equipment without PFC draws a surprising
amount of apparent power because of the poor power factor.
Due to the impedance of the AC mains wiring, the high peak currents associated with poor power factor
affect the wave shape of the mains voltage. This is a kind of harmonic distortion that can adversely affect
some types of equipment. For example, it's well known that the ubiquitous 60 Hz and 120 Hz magnetic
fields can couple to 'ground loops' and cause annoying hum. However the presence of significant mains
waveform distortion can make this sort of thing a problem at higher line harmonics (e.g., 180 Hz, 240 Hz,
etc.) where magnetic coupling is progressively more effective (proportional to frequency) and the hum is
increasingly annoying. Thanks, PM!]
Power over Ethernet See: PoE
PowerPC A super powerful RISC processor PC jointly developed by IBM, Apple and Motorola,
designed to run any PC operating system (MS-DOS, UNIX, Windows, OS/2, Mac OS. etc.). Featured in
Apple's line of "PowerMac" computers.
PPM (peak program meter) An audio meter originally developed in Europe to accurately measure and
display peak audio signals (as opposed to average audio signals; see VU meter). The PPM augments the
VU meter and it is normal to find both in modern recording studios. The PPM is particularly valuable for (14 of 18) [10/3/04 12:30:40 AM]
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digital audio recording or signal processing due to the critical monitoring required to prevent exceeding 0
dBFS and reducing overs. There are two standards: IEC 60268-10 for analog meters and IEC 60268-18
for digital meters. [These are available to buy on the IEC website.] An interesting aspect of PPM design
is that rather than respond instantaneously to peaks, they require a finite 5 ms integration time, so that
only peaks wide enough to be audible are displayed. IEC 60268-10 translates this into a response that is 1
dB down from steady-state for a 10 ms tone burst, 2 dB down for a 5 ms burst, and 4 dB down for a 3 ms
tone burst -- requirements satisfied by an attack time constant of 1.7 ms. The IEC specified decay rate of
1.5 seconds to a -20 dB level can be met with a 650 ms time constant.
Pramanik stylus Phonographs. A ultra-lightweight 4-channel phono cartridge with a Beryllium
cantilever and a multifaceted stylus invented by Subir "Pram" Pramanik of Bang & Olufsen in 1973.
Prandtl number See: Grashof.
preamplifier See amplifier
precedence effect See: Haas Effect
pre-echo See: print-through
pre-emphasis A high-frequency boost used during recording, followed by de-emphasis during playback,
designed to improve signal-to-noise performance.
pre-mastering See mastering
pressure gradient microphone See ribbon microphone
pressure zone microphone See PZM
pretzel A French horn. (Decharne)
print-through The name for the magnetic tape recording phenomena where the act of layering, or
winding layer upon layer of tape causes the flux from one layer to magnetize the adjacent layer, thus
printing through from one layer onto another layer. Also called crosstalk or interlayer transfer. The most
vulnerable parts of the magnetic tape are the blank spots, particularly leaders and spaces between material
that happen to occur adjacent to loud passages. Two other terms come from print-through: on layers
played back before loud passages it gives a pre-echo, whereas on playback following the loud passage it
gives a post-echo.
probability density function, or pdf, or p.d.f. The name given to a mathematical function that defines a (15 of 18) [10/3/04 12:30:40 AM]
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continuous interval (i.e., one without gaps), or curve, such that the area under the curve (and above the xaxis, i.e., the probability is always positive) described by the function is unity, or equals one, or 100% -whatever way you want to look at it. It simply means that all possibilities are represented. The most
familiar example is the famous "bell-shaped curve" or just "bell curve." The bell curve is a symmetrical
curve representing a normal or Gaussian distribution. Also called a normal curve. When applied to
school grading, for example, it says that there is the highest probability that a student picked at random
will receive a C-grade, and rapidly decreasing probabilities that any one student will receive a B- or Agrade, going in one direction, or a D- or F-grade, going in the other direction. Technically, it means the
probability of a random variable taking values between two real numbers, or extremes (an A or an F) is
given by the area under the curve between these two points.
production master See mastering
Programming, Law of The law states that every program contains at least one bug. The law further
states that every program can be shortened by at least one instruction. Therefore, the law concludes, every
program can be reduced to one instruction that does not work. The law is not wrong. [Thanks TP.]
progressive array See: line arrays
Project Planner Fun and educational tool developed by MC2 System Design Group. [Check it out, you
won't be disappointed.]
PROM (programmable read-only memory) A memory device whose contents can be electrically
programmed (once) by the designer.
proof "Evidence having a shade more of plausibility than of unlikelihood. The testimony of two credible
witnesses as opposed to that of only one." -- Ambrose Bierce.
propagation The motion of waves through or along a medium. For electromagnetic waves, propagation
may occur in a vacuum as well as in material media.
propagation delay The initial delay through a signal processing box, i.e., the time it takes for a signal to
pass once through a device. It is the unavoidable and uncontrollable (by the user) delay inherent to the
processing electronics. Propagation delay is caused most often in analog electronics by phase delay in
filter networks, and in digital electronics by computational delay in microprocessors and DSP devices, as
well as data conversion. In networking, the time it takes for a signal to pass through a channel. Similar to
latency but normally restricted to signal processing devices, rather than computer operations.
proportional-Q graphic equalizer (also variable-Q) Term applied to graphic and rotary equalizers
describing bandwidth behavior as a function of boost/cut levels. The term "proportional-Q" is preferred as
being more accurate and less ambiguous than "variable-Q." If nothing else, "variable-Q" suggests the unit (16 of 18) [10/3/04 12:30:40 AM]
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allows the user to vary (set) the Q, when no such controls exist. The bandwidth varies inversely
proportional to boost (or cut) amounts, being very wide for small boost/cut levels and becoming very
narrow for large boost/cut levels. The skirts, however, remain constant for all boost/cut levels. See
RaneNote: Operator Adjustable Equalizers. Compare with constant-Q and true response graphic
prosumer Shortened form of professional + consumer, often used to refer to home recording studio
protocol A specific set of rules, procedures or conventions relating to format and timing of data
transmission between two devices. A standard procedure that two data devices must accept and use to be
able to understand each other.
proximity effect Microphones. Term for the increase in low frequency response (bass boost), or
sensitivity, of most directional microphones when the sound source is within a few inches.
Pseudoacoustic Infector Term coined by Rane Corporation for their mythical product, the PI 14, first
introduced in 1988, which almost caught the attention of the music industry. An acoustic stimulator
designed to add a little bit of This and a little bit of That to recordings, to give them a sense of Now
previously unobtainable. Rane's PI 14 introduced a unique Here-to-There (and-Back-Again) pan control.
Transformer operation required the Jensen JE-EP-ERs when coupling directly into a Crown Belchfire BF6000SUX for playback through an Electro-Voice Rearaxial Softspeaker. Today, PI 14s are considered
quite scarce and highly collectable.
pseudo-balanced output A two-wire (with overall shield) interfacing technique for an unbalanced output
where a resistor equal to the output resistor is placed in series with the return leg (either pin-3 for an XLR
connector or the ring lead for an 1/4" TRS connector). This makes both lines measure the same
impedance when looking back from the receiver and allows the common-mode rejection feature of the
input differential amplifier to function. See RaneNote: Sound System Interconnection.
psophometric See: weighting filters
psst Only word in the dictionary without a vowel. "Used to capture someone's attention inconspicuously."
psychoacoustics The scientific study of the perception of sound. Called "the music of science" by
Roederer. (17 of 18) [10/3/04 12:30:40 AM]
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public address See P.A.
punch-in/punch-out Recording studio: To engage/disengage record mode on a track previously
recorded, usually for purposes of correcting unwanted segments.
PURLnet See ZigBee
purple One of the few words in the English language without a rhyme -- some others are "month,"
"orange" & "silver."
purple noise See noise color
PVC cable (polyvinyl chloride) The most common type of cable used when smoke retardant properties
are not required, i.e., when a building's HVAC system is run through metal ducts - not open ceilings. This
cable is sheathed in PVC, the standard jacketing of most electrical cable. PVC is a tough water and flame
retardant material, but is not smoke retardant. If PVC catches fire, it emits noxious gases, and if the cable
is run in a plenum area, the deadly gases can be dispersed throughout the building.
PWM (pulse width modulation) A conversion method in which the widths of pulses in a pulse train
represent the analog information. See RaneNote: Digital Dharma of Audio A/D Converters
Pythagorean temperament The mathematical principles of musical harmony according to the Greek
philosopher Pythagoras.
PZM (pressure zone microphone) Patented by Ed Long & Ron Wickersham in 1982, a technique and
design where the microphone is mounted on a flat plate which acts as a reflective surface directing sound
into the mic capsule. The PZM principle uses the compression and decompression of air between the
plate and the membrane in parallel with the plate (the gap is very narrow, typically only a millimeter or
less. This arrangement gives about 6 dB extra amplification of the signal, which means 6 dB less inherent
electronic noise. Now owned by Crown (recently acquired by Harman)
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q (lower-case) Physics. The symbol for charge.
Q (upper-case) Quality factor. Filters. The selectivity factor defined to be the ratio of the center
frequency f divided by the bandwidth BW. See RaneNote: Constant-Q Graphic Equalizers; also
download "Bandwidth vs. Q Calculator" as a zipped Microsoft Excel spreadsheet in the Rane Library.
Q-8 RCA's name for their 4-channel, eight-track tape cartridges, the world's first (and last). For photo,
see Discrete Four-Channel Sound on Magnetic Tape
QoS (quality of service) 1. The performance specification of a communications channel or system. It
may be quantitatively indicated by channel or system performance parameters, such as signal-to-noise
ratio (S/N), bit error ratio (BER), message throughput rate, and call blocking probability. 2. A subjective
rating of telephone communications quality in which listeners judge transmissions by qualifiers, such as
excellent, good, fair, poor, or unsatisfactory. [From Federal Standard 1037C]
QS Sansui's name for their quadraphonic sound system using a proprietary matrixing algorithm for
encoding four-channel sound down to two-channels. See Matrix Quad. Compare with SQ
QSound The name of a Canadian company and its proprietary and patented 3D sound technology.
Designed for two channel playback systems, QSound finds success in the computer and arcade game
markets, as well as movie theaters. Using advanced signal processing techniques, QSound adds
localization cues to the original material. Since loudspeakers and headphones create quite different
playback environments, different algorithms exist for each. QSound allows the music producer to locate
specific sound events in virtual positions outside the physical locations of the two loudspeakers. The
effect is primarily one of widening the sound field. QSound works best when the listener is positioned in
the sweet spot located equidistant between the speakers.
quackery The statement floating about cyberspace that a duck's quack does not echo and no one knows
quad flat pack The most commonly used package in surface mount technology to achieve a high lead
count in a small area. Leads are brought out on all four sides of a thin square package. (1 of 3) [10/3/04 12:30:44 AM]
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quad mic cable See cables.
quadraphonic sound Coined in the '70s, the original term for surround sound.
quadratic residue diffuser A type of Schroeder diffuser consisting of a plane surface with an array of
parallel slots all the same width but with varying depths based on a prime number mathematical
quadrature A state of separation or relationship equal to 90°. For example, two same frequency sine
waves one-quarter wavelengh apart are in quadrature. A phase difference equal to one-fourth of a period.
quality factor See: Q.
quantization distortion Same as quantization error below.
quantization error Error resulting from quantizing an analog waveform to a discrete level. It is the
difference between the actual value of the analog signal at the sampling instant and the nearest
quantization value. Therefore, in general, the longer the word length, the less the error, because there are
more step sizes to choose the closest. See also SQNR and RaneNote: Digital Dharma of Audio A/D
quantization The process of converting, or digitizing, the almost infinitely variable amplitude of an
analog waveform to one of a finite series of discrete levels. Performed by the A/D converter. See also
SQNR and RaneNote: Digital Dharma of Audio A/D Converters
quantum dot A confined and isolated atom such that the removal or addition of a single electron can be
detected, i.e., its properties change in a detectable manner -- the ultimate memory cell. In
nanotechnology, they are called quantum bits or qubits.
quarter-inch jack Same as ¼" TRS or ¼" TS, see connectors.
quartz crystals Electronics.A small crystal of quartz accurately cut along certain axes so that it can be
vibrated at a particular frequency, used for its piezoelectric properties to produce an electric signal of
constant known frequency. (AHD) See: piezo.
quasi- To some degree; in some manner: quasi-stellar object. (AHD)
quasi-balanced line See: floating unbalanced line
quasi-parametric See: parametric equalizer (2 of 3) [10/3/04 12:30:44 AM]
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quasi-peak detector Electronics. A detector having specified electrical time constants that, when
regularly repeated pulses of constant amplitude are applied to it, delivers an output voltage that is a
fraction of the peak value of the pulses, the fraction increasing toward unity as the pulse repetition rate is
increased. (IEEE) In other words, a peak detector with a long time constant.
quaternary The word that comes after primary, secondary, tertiary.
quinary The word that comes after primary, secondary, tertiary, quaternary.
qubits See: quantum dot above.
Queen, Daniel (1934-2002) Long-time Standards Manager for the AES, Daniel had a full and productive
audio career including his successful consulting company, Daniel Queen Associates, specializing in
electroacoustics, architectural acoustics, and noise control. He joined the AES in 1962 and became a
fellow in 1970.
quiescent noise Another name for a product's residual noise or noise floor.
quieting sensitivity FM Radio. (Also called IHF Sensitivity.) In simple terms it is the minimum input
signal required to provide a distortion-free listenable output signal. In technical terms, it is "the minimum
unmodulated signal input for which the output signal-to-noise ratio does not exceed a specified limit,
under specified conditions." (IEEE) This test was standardized in 1958 by the IHF (Institute of High
Fidelity) to mean the unmodulated carrier amplitude measured in microvolts (rms) required for a specific
dB reduction in output noise over the output noise present with no-signal. A typical specification might
read: 0.5 microvolts for 20-dB quieting. Also measured in femtowatts (dBf).
quint Music. Name for an interval of a fifth.
quintessence In ancient and medieval philosophy, the fifth and highest essence after the four elements
of earth, air, fire, and water, thought to be the substance of the heavenly bodies and latent in all things.
QWERTY Nickname for the computer (or typewriter) keyboard derived from the left side, top row of
letter keys.
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racket A loud distressing noise. [AHD]
rack unit See "U"
radian 1. Mathematics. A unit of angular measure equal to the angle subtended at the center of a circle
by an arc equal in length to the radius of the circle, approximately 57°17'44.6 (AHD) 2. Filters.
Frequency is measured in radians/second. One cycle (360°) equals 2 pi radians.
radiation error Loudspeakers. All inclusive term describing the total lobing and cancellation error
occurring in a loudspeaker response due to crossover and multiple driver effects. An ideal crossover
applied between two sources would exhibit no lobing error and no cancellations off axis. (Coined by
Justin Baird and David McGrath, Lake Technology, in their paper "Practical Application of Linear
Phase Crossovers with Transition Bands Approaching a Brick Wall Response for Optimal Loudspeaker
Frequency, Impulse and Polar Response," presented at the 115th Convention of the Audio Engineering
Society, New York, NY October 10-13, 2003, Preprint 5885.)
radicalism "The conservatism of tomorrow injected into the affairs of today." -- Ambrose Bierce.
radix Mathematics. The number base, such as 2 in the binary system and 10 in the decimal system.
radix point The binary equivalent of the decimal point -- think of it as a "binary point."
rail-switcher A term used to describe audio power amplifier designs utilizing more than one power
supply for the output, and a means of switching between them based upon the input signal. This scheme
improves efficiency. See: Class G Amplifiers and compare with tracking power amplifiers.
rail-to-railTM Registered trademark of Nippon Motorola, Ltd. for their op amp designs having
maximum input and output levels equal to the power supply voltages. See RRIO
raised cosine filter A low-pass filter found most often in data communication systems. A perfect raised
cosine filter is characterized by a frequency response that is symmetrical about 0 Hz, with a flat low (1 of 11) [10/3/04 12:30:50 AM]
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frequency passband, then a smooth rolloff following a cosine curve to zero through the transition region
and staying at zero (infinite attenuation) throughout the stopband. The response of real world filters
(usually DSP FIR designs) approximate this response, with the most noticeable deviation being ripple in
the transition region, limiting attenuation to, say, 70 dB, or so, depending on the number of filter taps
used. The first known use of this technology in pro audio occurred with a proprietary filter based on
raised cosine design used in the Lake Contour system.
RAM (random access memory) A memory device in which data may be read out and new data written
into any address or location.
RaneNotes A series of technical notes written by Rane's technical staff.
RaneWareTM A registered trademark of Rane Corporation used to identify Rane software products -not something to keep you dry.
Rankine scale A scale of absolute temperature using degrees the same size as those of the Fahrenheit
scale, in which the freezing point of water is 491.69° and the boiling point of water is 671.69°. After
William John Macquorn Rankine below. [AHD. Sounds handy to me. ]
Rankine, William John Macquorn (1820-1872), Scottish engineer and physicist.
RAQ (rarely asked questions) The really important questions that should be asked, but never are. The
answers to RAQs are kept hidden within government and corporate walls.
rarefaction 1. A decrease in density and pressure in a medium, such as air, caused by the passage of a
sound wave. 2. The region in which this occurs. (AHD)
RASTI (rapid speech transmission index) A speech intelligibility performance standard (IEC 6026816). Developed in 1973 by Dr. Steeneken in Holland, it is a simpler alternative to the more complex STI
(speech transmission index). See B&K Note; also Peter Mapp's excellent AES preprint 5668 presented
at the 113th Convention of the Audio Engineering Society, Los Angeles, October 2002. Compare with
RC (room criteria) rating A new noise criteria adopted by ASHRAE to replace the NC criteria. The RC
rating is based on ASHRAE sponsored studies of preference and requirements for speech privacy ratings
for "acoustical quality." RC ratings contain both a numerical value and a letter to describe the expected
spectral quality of the sound. The numerical part is called the speech interference level (SIL) equal to the
arithmetic average of the measured SPL in the 500 Hz, 1 kHz and 2 kHz octave bands, and the letter part
denotes the timbre or sound quality as subjectively described by an observer as neutral (N), rumbly (R),
hissy (H) or acoustically induced vibration noise (RV). The RC curves serve as optimum spectrum (2 of 11) [10/3/04 12:30:50 AM]
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shapes for background sound in buildings. Octave band analysis that meet a specific RC curve are
considered neutrally balanced, i.e., they have the desired amounts of low-, mid- and high-frequency
content to be heard as not offensive. RC curves are straight lines set at -5 dB/octave slopes (of course -couldn't be 6, had to be 5). The RC rating standard is Criteria for Evaluating Room Noise, ANSI S12.2.
See Trane's excellent summary "How To Determine The RC Noise Rating," for a step-by-step tutorial.
And for a more formal comparison between the NC and RC methods see University of Colorado Prof.
Ralph T. Muehleisen's notes "Room Noise Criteria: NC and RC Methods"
RCA jack See connectors.
RCDDTM (Registered Communications Distribution Designer) A designation for individuals who
demonstrate expertise in the design, integration, and implementation of telecommunications (voice, data,
video, audio, and other low-voltage control) transport systems and their related infrastructure
R-DAT or DAT (rotary head digital audio tape recorder) A digital audio recorder utilizing a magnetic
tape cassette system similar to that of a video recorder.
reactance The imaginary part of an impedance.
Reado The name of the first FAX machine, introduced by Crosley Radio in 1940.
reality "Reality is that which, when you stop believing in it, doesn't go away." -- Philip K. Dick
real-time analyzer See RTA
real-time operation What is perceived to be instantaneous to a user (or more technically, processing that
completes in a specific time allotment).
re-amping Originally this term meant to take an already recorded guitar sound and use it to drive
another different sounding guitar amp -- literally re-amplifying it as a means of changing the original
recorded sound. Now used on any recorded sound with a real amplifier or virtual plug-in.
rearaxial softspeaker Term coined by Electro-Voice for their mythical loudspeaker, the
SP13.5TRBXWK. Claimed by many to be the speaker that couldn't be made, it might have changed all
future loudspeaker design, but it didn't. Characterized by being undirectional, the designer's claimed it
produced silken highs and woolen lows. The only loudspeaker known to incorporate both "presence" and
"absence" controls. Based on a ridiculously simple principle that still cannot be explained, the
SP13.5TRBXWK was only heard once, during the Rane demo of their PI 14 Pseudoacoustic Infector,
coupled by a Jensen JE-EP-ERs Multi-denomial Transpedance Informer to a Crown Belchfire BF- (3 of 11) [10/3/04 12:30:50 AM]
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6000SUX amplifier. No one survived.
reconing Loudspeakers. The act of replacing a blown, torn, or cracked cone on a dynamic loudspeaker -a highly skilled operation. See Loudspeaker Reconing by Thomas P. Colvin for details.
reconstruction filter A low-pass filter used at the output of digital audio processors (following the
DAC) to remove (or at least greatly attenuate) any aliasing products (image spectra present at multiples
of the sampling frequency) produced by the use of real-world (non-brickwall) input filters.
Recording Academy, The The organization formerly known as NARAS. Think Grammy; often
confused with SPARS.
recording console See: mixer
recording technology history See site posted by Steve Schoenherr
recording terminology See: Recording Institute of Detroit, who claims to have posted the largest
glossary of recording terms on the web.
rectifier An electronic component used to convert from alternating current (AC) to direct-current (DC).
Works by only conducting current in one direction which allows inversion or suppression of alternate
half cycles. Several types exist from early selenium rectifiers to modern semiconductor diodes. See: fullwave and half-wave
recursive A data structure that is defined in terms of itself. For example, in mathematics, an expression,
such as a polynomial, each term of which is determined by application of a formula to preceding terms.
(AHD) Pertaining to a process that is defined or generated in terms of itself, i.e., its immediate past
Red Book Nickname for the Philips and Sony's ECMA-130 standard document that defines the format
for CD-Audio (compact disc-digital audio) discs; available only to licensees. Compare with Green Book
and Yellow Book
red noise See noise color
reflection Acoustics. Sound that is reflected. See link.
reflectors In acoustics, an object or surface that reflects, or bounces back the original signal. A perfect
reflector would reflect with no loss of energy. A diffuser is a special kind of reflector. (4 of 11) [10/3/04 12:30:50 AM]
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refraction Acoustics. The bending of sound waves caused by entering a medium where the speed of
sound is different. See link.
reggae Music. Jamaican English, ragged clothing. Popular music of Jamaican origin having elements of
calypso and rhythm and blues, characterized by a strongly accentuated offbeat. (AHD)
reggaetonMusic. A new genre of dance music characterized by Entertainment Weekly as"a Spanishlanguage, pan-American fusion of Stateside hip-hop rhymes, Puerto Rican salsa flourishes, and Jamaican
dancehall rhythms.". Compare with Jawaiian.
REL (Rights Expression Language) A unified vocabulary for individuals to express copyright law
release Audio Compressors. How fast the gain is turned back up once the signal drops below the
threshold setting. Contrast with attack.
resistance See impedance
resistor standard values See: values
resonance 1. Electronics. In an LRC circuit, it is the condition where the inductive and capacitive
reactances are equal; this is called the resonant frequency. 2. Physics. The increase in amplitude of
oscillation of an electric or mechanical system exposed to a periodic force whose frequency is equal or
very close to the natural undamped frequency of the system. (AHD) A dynamic condition which occurs
when any input frequency of vibration coincides with one of the natural frequencies of the structure. That
is, the inclination of any mechanical or electrical system to vibrate (resonate) at a certain frequency when
excited by an external force, and to keep vibrating after the excitation is removed. 3. Acoustics.
Intensification and prolongation of sound, especially of a musical tone, produced by sympathetic
vibration. 4. Linguistics. Intensification of vocal tones during articulation, as by the air cavities of the
mouth and nasal passages. (AHD)
resonant frequency Electronic Circuits. See above.
retro audio Termed coined by Tomlinson Holman of THX fame, referring to new audio gear designed
using legacy or old technology, usually tubes, with cosmetics to match.
return loss Category wiring. The ratio of the transmitted signal strength to the reflected signal strength.
A characteristic often degraded due to excessive bending of the cable.
reverb Recording. Shortened form of reverberator, or reverberation unit. Any electronic or acoustical (5 of 11) [10/3/04 12:30:50 AM]
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device designed to simulate, or capture, the natural reverberation of a large hard-surfaced (echoic) room,
and mix it back with the original recorded sound. Reverb today is accomplished by digital devices using
complex DSP algorithms; previously done using a chamber, a plate, or springs.
reverberation The total sound field remaining in a room after the original source is silenced. The length
of time of this collapsing sound field is called the reverberation time and is defined below. Contrast with
echo and ambience. "Reverberation represents the energy decay process after the initial echoes"
reverberation time also RT60 Reverberation is all sound remaining after the source stops. The time it
takes for this sound to decay is called the reverberation time, and it is quantified by measuring how long
it takes the sound pressure level to decay to one-millionth of its original value. Since one-millionth
equals a 60 dB reduction, reverberation time is abbreviated "RT60."
RFI (radio frequency interference) A measure of radio frequency (RF) radiation from equipment. An
RF disturbance is an electromagnetic disturbance having components in the RF range.
RFID (radio frequency identification) Technology using RF signals to ID individuals. It uses silicon
chip tags with radio frequency functions and on-board memory that holds unique ID numbers, allowing it
to ID and track just about anything.
RF-Lite See ZigBee
rhythm The only English language word containing two syllables with no natural vowels. [Thanks GS.]
RIAA (Recording Industry Association of America) A professional trade organization representing the
U.S. recording industry. RIAA® members create, manufacture and/or distribute approximately 90% of
all sound recordings produced and sold in the United States.
RIAA equalization curve The standard first proposed by the RIAA (see above) and adopted by the disc
recording industry in 1953, reaffirmed in 1964 by both the RIAA and NAB and issued as international
standard IEC 60098 (old IEC 98) by the IEC, which remains in effect today. The curve is used in cutting
vinyl records and its inverse is required in phono playback preamplifiers. The curve attenuates low
frequencies and amplifies high frequencies (relative to a 1 kHz reference point) in order to achieve the
maximum dynamic range for a lateral cut vinyl disc (as opposed to the older method of vertical cutting).
The grooves in a stereo phonograph disc are cut by a chisel shaped cutting stylus driven by two vibrating
systems arranged at right angles to each other. The cutting stylus vibrates mechanically from side to side
in accordance with the signal impressed on the cutter. The resultant movement of the groove back and
forth about its center is known as groove modulation. The amplitude of this modulation cannot exceed a
fixed amount or "cutover" occurs. Cutover, or overmodulation, describes the breaking through the wall of
one groove into the wall of the previous groove. Since low frequencies cause wide undulations in the (6 of 11) [10/3/04 12:30:50 AM]
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groove, they must be attenuated to prevent overmodulation. At the other end of the audio spectrum, high
frequencies must be amplified to overcome the granular nature of the disc surface acting as a noise
generator, thus improving signal-to-noise ratio.
ribbon microphone Invented in 1923 by Walter Schottky (the same German physicist who invented the
famous diode) and Erwin Gerlach of Siemens Halske (German pioneering telegraph company), it is
constructed using a very thin metal foil ribbon (~0.002 mm [really] and pleated or corrugated to reduce
its longitudinal stiffness, to obtain the lowest resonant frequency so the ribbon is mass-controlled)
attached between the poles of a permanent magnet. The acoustic signal (sound pressure variation) causes
the ribbon to move and interact with the stationary magnetic field inducing a voltage into the ribbon
proportional to the amplitude and frequency of the audio signal.
Also called velocity microphone or pressure gradient microphone. These names come about from the
physical action of the air particles hitting the ribbon. The motion of the ribbon is proportional to the
velocity of the air particles striking it, due to its mass being so small that its resonant frequency is
infrasonic (2-4 Hz); looked at another way, it responds to the air particle velocity which is developed by
the pressure gradient, i.e., the difference in air pressure between the two sides of the ribbon (both sides
of the ribbon are open to the atmosphere) causes the ribbon to move.
[Historical Note: In 1931, Harry F. Olson, along with Frank Massa, successfully developed the first
commercial ribbon microphone based on Schottky & Halske's patent filed eight years earlier on ribbon
loudspeaker and microphone theory. They received a US patent for the first cardioid ribbon microphone
using a field coil instead of a permanent magnet. Because of this Olson is usually credited as the
inventor of ribbon microphones, even though this is historically incorrect.]
ribbon tweeter Also invented by Schottky and Gerlach simply by reversing the physical effects of their
microphone; it is the inverse of the ribbon microphone described above. It creates a high frequency
loudspeaker consisting of a paper-thin metal foil ribbon suspended in a magnetic field (i.e., placed
between the poles of a permanent magnet). The audio voltage signal drives the ribbon causing a current
to flow creating a magnetic field that reacts with the stationary magnet to create sound proportional to the
applied waveform. Very similar in principle to the dynamic loudspeaker, only much smaller, with the
ribbon replacing the voice coil and cone arrangement.
Rickenbacker Guitars. Name for the company credited with producing the first commercially available
electric guitar in 1931 (ten years before Les Paul's innovations). The company was founded by Adolph
Rickenbacker (WWI flying legend Eddie Rickenbacker's cousin) and George D. Beauchamp with the
original name of the Electro String Instrument Corporation.
Ricky Guitars. Nickname for Rickenbacker guitars (see above).
Rights Expression Language See: REL.
ring it up Phrase coined from the first cash registers that ran a bell for emphasis when the drawer (7 of 11) [10/3/04 12:30:50 AM]
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opened, signifying the end of the calculation.
ring out Acoustics. Shorten form of "ring out a room," slang meaning for locating and treating a sound
system's resonant and feedback frequencies.
ring-right-red Old mantra from the early telephone days meaning the ring of a telephone jack always
connects to the right terminal, and is red. Now used by audio designers and installers to remind that the
right channel is always the ring in a 1/4" TRS connector and the red RCA phono jack and cable.
ring topology A network topology where all nodes are daisy chained together (connected) in a closed
RISC (reduced instruction set computer) A computer design that achieves high performance by doing
the most common computer operations very quickly, utilizing a high speed processing technology that
uses a far simpler set of operating commands. Primarily found in workstations and PowerPCs. The
alternative to CISC (complex instruction set computing), the original way of doing computing.
RJ (Registered Jacks) As in red RJ-12 modular telephone jacks used by Rane Corporation for external
power supply connection.
RLA (ribbon line array) See: SLS Loudspeakers' white paper; also see: line arrays
RLA (Richard Long Associates) See Long
rms See: root mean square
rms power No such thing. A misnomer, or application of a wrong name. There is no such thing as "rms
power." Average or apparent power is calculated using rms values but that does not equal "rms power;"
it equals continuous sine wave power output into a resistive load.
road dog Live Sound. Someone always on the road working as a sound mixer or other live sound jobs.
See Dave Stevens’ Roaddog website. Slang. Homey, homeslice, partner, buddy, cool one, friend,
traveling companion.
rock crusher Accordion. (Decharne)
rock journalism See: Zappa.
rolloff rate Filters. The rate at which low-pass, high-pass and bandpass filters attenuate frequencies not
in the passband. Expressed in dB/octave, it is a measure of the attenuation slope. Slopes occur in 6 (8 of 11) [10/3/04 12:30:50 AM]
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dB/octave increments (due to the natural storage effects of capacitors and inductors), e.g., 12 dB/oct, 18
dB/oct, 24 dB/oct, etc.
ROM (read-only memory) A memory from which data, after initial storage, may only be read out, but
new data cannot be written in. The normal audio CD is an example of a read-only system.
room modes or eigentones (from German eigen meaning "self" or "own") Acoustics. The acoustic
resonances (or standing waves) in a room (or any enclosed space) caused by parallel surfaces. It is the
dimensional resonance of a room, where the distance between the walls equals half the wavelength of the
lowest resonant frequency (and resonates at all harmonic frequencies above it). Room modes create
uneven sound distribution throughout a room, with alternating louder and quieter spots.
root mean square Abbr. rms (lowercase) Mathematics. The square root of the average of the squares of
a group of numbers. (AHD) A useful and more meaningful way of averaging a group of numbers.
ro-ro Short for road dog
Rosie DJ Mixers. First stereo DJ mixer developed by Alex Rosner, named after the designer and for its
red paint.
Roswell, NM The truth about what really went on at this Army Air Field is much better than the
Hollywood fiction. Click on the link and read all about it.
rotary equalizer A multi-band variable equalizer using rotary controls as the amplitude adjustable
elements. Both active and passive designs exist with rotary controls. Center frequency and bandwidth are
fixed for each band.
router An audio device used to selectively assign any input to any output, including the ability to add
inputs together. In this way, one input could go to all outputs, or all inputs could go to just one output, or
any combination thereof. An n x m matrix forms the core of any router, where there are n inputs and m
outputs. Typically, level controls are provided on all inputs and outputs; balanced and unbalanced
designs exist. More elaborate designs are called matrix-mixers.
Royal Device subwoofer Link for the ultimate subwoofer.
RPM (Remote Programmable Multiprocessor)TM Rane Corporation's trademark for their line of DSP
multiprocessor-based digital audio signal processing devices.
RRIO (rail-to-rail input & output) Term created to indicate op amps with maximum input and output
levels equal to the power supply voltages, without violating the registered term rail-to-rail®. (9 of 11) [10/3/04 12:30:50 AM]
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RS (Recommended Standard) As in RS-232 serial interface standard, et al.
RS-232 The standard serial interface (EIA/TIA-232-E)used on most personal computers. A format
widely supported for bidirectional data transfer at low to moderate rates. The most common interface
method used to connect personal computers with peripheral hardware and instruments. Use is restricted
to one peripheral at a time and short distances. The standard originally called for DB-25 connectors, but
now allows the smaller DB-9 version.
RS-422 The standard adopted in 1978 by the Electronics Industry Association as EIA-422-A, Electrical
characteristics of balanced voltage digital interface circuits. A universal balanced line twisted-pair
standard for all long distance (~1000 m, or ~3300 ft) computer interconnections, daisy-chain style. [See
NSC AN 759 for RS-422 vs. RS-485 comparison.]
RS-485 The standard describing the electrical characteristics of a balanced interface used as a bus for
master/slave operation. Allows up to 32 users to bridge onto the line (as opposed to RS-422's need to
daisy chain the interconnections). Same as EIA-485. [See NSC AN 759 for RS-422 vs. RS-485
RS-490 The standard adopted in 1981 by the EIA entitled Standard Test Methods of Measurement for
Audio Amplifiers. The power amp testing standard for consumer products.
RT60 See: reverberation time
RTA (real-time analyzer) A constant percentage bandwidth spectrum analyzer. For example, see Rane
RA 30 .
RU (rack unit) See "U"
rumble A quantitative measure of phonograph turntable noise and vibration resulting from performance
imperfections. The RMS voltage is measured at the cartridge while playing a blank (silence) record, and
the answer expressed in dB below a reference point.
rumble filter See infrasonic filter
RW 232TM (also RaneWare) A trademark of Rane Corporation used to identify Rane's RS-232-based
variant of the PA-422 AES standard.
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Pro Audio Reference
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70 volt line See: constant-voltage
SAA (semantic audio analysis) The automatic extraction of meaning from audio and the means for
representing it, typically as metadata.
sabin A non-metric unit of sound absorption used in acoustical engineering. One sabin is the sound
absorption of one square foot (or one square meter -- a metric sabin) of a perfectly absorbing surface-such as an open window. The sound absorption of a wall or some other surface is the area of the surface,
in square feet, multiplied by a coefficient that depends on the material of the surface and on the
frequency of the sound. These coefficients are carefully measured and tabulated. The unit honors Wallace
Sabine (see below). Sabine used this unit, which he called the open window unit (owu), as early as 1911.
[From Rowlett's How Many? A Dictionary of Units of Measurement]
Sabine, Wallace Clement Ware (1868-1919) American physicist and Harvard University professor who
founded the systematic study of acoustics around 1895. Regarded as the father of the science of
architectural acoustics.
SACD® (Super Audio CD®) Also known as DSD® or Direct Stream Digital®, joint trademark of Sony
and Philips for their proposal for the next generation CD-standard. Sony and Philips have split from the
DVD ranks to jointly propose their own solution comprised of a 1-bit, 64-times oversampled directstream digital SACD format. The original SACD proposal was for a hybrid disc comprising two layers: a
high density (HD) DSD layer in the middle, and a standard density CD layer at the bottom. The two
layers are read from the same side of the disc; the CD laser reads the bottom reflective layer through the
semi-transmissive HD layer, while the middle layer is read by the HD laser delivering high-quality,
multichannel sound without sacrificing backward compatibility. The HD layer has three tracks: the
innermost is for two-channel stereo; the middle is a six-channel mix; and the outer is for such additional
information as liner notes, still images and video clips. Maximum playing time is 74 minutes. This
proposal turned out to be too expensive, so the SACD first release is a single-layer SACD-only disc.
SAE (Society of Automotive Engineers) The international trade organization comprised of 80,000
engineers, business executives, educators, and students representing 100 countries that functions as the
resource for technical information and expertise used in designing, building, maintaining, and operating
self-propelled vehicles for use on land or sea, in air or space. (1 of 19) [10/3/04 12:30:57 AM]
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sample rate conversion The process of converting one sample rate to another, e.g. 44.1 kHz to 48 kHz.
Necessary for the communication and synchronization of dissimilar digital audio devices, e.g., digital
tape machines to CD mastering machines.
sample-and-hold (S/H) A circuit that captures and holds an analog signal for a finite period. The input
S/H proceeds the A/D converter, allowing time for conversion. The output S/H follows the D/A
converter, smoothing glitches.
Sampling (Nyquist) Theorem A theorem stating that a bandlimited continuous waveform may be
represented by a series of discrete samples if the sampling frequency is at least twice the highest
frequency contained in the waveform. See RaneNote: Digital Dharma of Audio A/D Converters
sampling frequency or sampling rate The frequency or rate at which an analog signal is sampled or
converted into digital data. Expressed in Hertz (cycles per second). For example, compact disc sampling
rate is 44,100 samples per second or 44.1 kHz, however in pro audio other rates exist: common examples
being 32 kHz, 48 kHz, and 50 kHz. [Historical note re 44.1 kHz vs. 44.056 kHz: Since the first
commercial digital audio recorders used a standard helical scan video recorder for storage, there had to
be a fixed relationship between sampling frequency and horizontal video frequency, so these frequencies
could be derived from the same master clock by frequency division. For the NTSC 525-line TV system, a
sampling frequency of 44,055.94 Hz was selected, whereas for the PAL 625-line system, a frequency of
44,100 Hz was chosen. The 0.1% difference shows up as an imperceptible pitch shift.] See RaneNote:
Digital Dharma of Audio A/D Converters
sampling The process of representing the amplitude of a signal at a particular point in time.
SAN (storage area network) A network connecting host computers to storage servers and systems. SAN
technology allows high-speed connection of multiple workstations to a centralized hard-disk network
(via fiber optics interconnection), allowing each workstation to access any drive from any location (e.g.,
control rooms in DAW recording studios).
SAR (successive approximation register) A type of analog-to-digital converter using a digital-to-analog
converter to determine the output word successively, bit by bit.
sawtooth wave A periodic waveform characterized by a 50% duty cycle and a Fourier series consisting
of both even- and odd-ordered, equal phase, sinusoidal harmonic components of its fundamental
frequency. The amplitudes (coefficients multiplying the magnitude of the fundamental sine wave) of the
odd-ordered harmonics are the same as a square wave, while the amplitudes (re the fundamental) for the
even-ordered harmonics are -1/n, where n is the even harmonic number. Therefore the first few even
harmonic multipliers are -1/2, -1/4, -1/6, ... etc., and the first few odd harmonic multipliers are 1/3, 1/5,
1/7, ... etc. (2 of 19) [10/3/04 12:30:57 AM]
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Sax, Adolphe (1814-1894) Belgian musical instrument designer and inventor of the saxophone.
scat Jazz singing using sounds instead of words. A scat singer is defined by Down Beat's Yearbook of
Swing, 1939 as a "vocalist who sings rhythmically, but without using accepted English words."
Schottky, Walter (1886-1976) German physicist whose work in solid-state physics and electronics
resulted in many inventions that bear his name (Schottky effect, Schottky barrier, Schottky diode). He also
invented the tetrode and (with Erwin Gerlach) the ribbon microphone and ribbon tweeter.
Schroeder diffuser See: diffuser.
SCMS (pronounced "scums") (serial copy management system) The copy protection scheme applied to
consumer digital recording equipment - it does not apply to professional machines. This standard allows
unlimited analog-to-digital copies, but only one digital-to-digital copy. This is done by two control bits
(the C and L bits) contained within the digital audio data.
screech analysis Serious but fun analysis done by MC2 System Design Group. [Check it out; you won't
be disappointed.]
screeched The longest one-syllable word in the English language.
scrim Theater. A transparent fabric used as a drop in the theater to create special effects of lights or
atmosphere. (AHD)
SCSI port (pronounced "scuzzy") (small computer system interface) A standard 8-bit parallel interface
used to connect up to seven peripherals, such as connecting a CD-ROM player or document scanner to a
SD (super density compact disc) See: DVD
SDDS® (Sony Dynamic Digital Sound) Sony's competing format for the digital soundtrack system for
motion picture playback. The signal is optically printed outside the sprocket holes, along both sides of
the print. Sony recently developed a single camera system that records all three digital formats (Dolby
Digital, DTS & SDDS) on a single inventory print, thus setting the stage for long term coexistence of all
SDIF (Sony digital interface format) Sony's professional digital audio interface utilizing two BNC-type
connectors, one for each audio channel, and a separate BNC-type connector for word synchronization,
common to both channels. All interconnection is done using unbalanced 75 ohm coaxial cable of the (3 of 19) [10/3/04 12:30:57 AM]
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exact same length (to preserve synchronization), and is not intended for long distances.
SDMI (Secure Digital Music Initiative) A multi-industry group defining a specification to protect digital
music distribution.
segue Music. To make a transition directly from one section or theme to another. (AHD)
self-noise Microphones. Residual noise, or the inherent noise level of a microphone when no signal is
present. Microphone inherent self-noise is usually specified as the equivalent SPL level which would
give the same output voltage, with typical values being 15-20 dB SPL.
SEMA (Specialty Equipment Market Association ) An organization for the producers and marketers of
specialty equipment products and services for the automotive aftermarket. Today's group grew out of the
original SEMA started in 1963, known then as the "Speed Equipment Manufacturers Association" and
includes aftermarket audio manufacturers.
semitone Music. An interval equal to a half tone in the standard diatonic scale. Also called half step, half
tone. (AHD)
sensitivity 1. Audio electromechanics. The standard way to rate audio devices like microphones,
headphones and loudspeakers. A standard input value is applied and the resultant output is measured and
loudspeaker sensitivity: the standard is to apply one watt and measure the sound pressure
level (SPL) at a distance of one meter.
headphone sensitivity: the standard is to apply one milliwatt and then measure the sound
pressure level at the earpiece (using a dummy head with built-in microphones). See
RaneNote: Understanding Headphone Power Requirements.
microphone sensitivity: the standard is to apply a 1 kHz sound source equal to 94 dB SPL
(one pascal) and then measure the output level and express it in mV/PA (millivolts per
pascal). 2. Audio electronics. The minimum input signal required to produce a standard
output level.
power amplifier sensitivity: The input level required to produce one watt output into a
specified load impedance, usually 4 or 8 ohms.
radio receiver sensitivity: The input level required to produce a specified signal-to-noise
serial interface A connection which allows transmission of only one bit at a time. An example in the PC
world is a RS-232 port, primarily used for modems and mice. A serial interface transmits each bit in a
word in sequence over one communication link. See also: parallel interface. (4 of 19) [10/3/04 12:30:57 AM]
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serializer A parallel-to-serial data converter; used in buses and networks.
server A shared master computer on a local area network (LAN) used to store files and distribute them to
clients upon demand.
servo-loop; servo-locked loop; servo-mechanism A self-regulating feedback system or mechanism.
Typically a feedback system consisting of a sensing element, an amplifier, and a (servo)motor, used in
the automatic control of a mechanical device (such as a loudspeaker). In audio, usually the name applies
to a class of electronic control circuits comprised of an amplifier and a feedback path from the output
signal that is compared with a reference signal. This topology creates an error signal that is the difference
between the reference and the output signal. The error signal causes the output to do whatever is
necessary to reduce the error to zero. A loudspeaker system with motional feedback is such a system. A
sensor is attached to the speaker cone and provides a feedback signal that is compared against the driving
signal to create more accurate control of the loudspeaker. Another example is Rane's servo-locked
limiter™ which is an audio peak limiter circuit where the output is compared against a reference signal
(the threshold setting) creating an error signal that reduces the gain of the circuit until the error is zero.
servo-locked limiterTM Rane Corporation trademark for their proprietary limiter circuit. See: servoloop
SFDR (spurious free dynamic range) A testing method used in quantifying high-speed data converters
and high-frequency communication integrated circuits. It is the difference in dB between the desired
output signal and any undesired harmonics found in the output spectrum. See Intersil Application Note
TB326 for measuring details.
Shannon, Claude E. (1916-2001) American mathematician and physicist who is credited as the father of
information theory (For the mathematically advanced, see his famous paper, "A Mathematical Theory of
Communication" published in 1948 in The Bell ) . In his master's thesis Shannon showed how an algebra
invented by the British mathematician, George Boole in the mid-1800s could represent the workings of
switches and relays in electronic circuits. His paper has been called "possibly the most important master's
thesis in the century." See RaneNote: Digital Dharma of Audio A/D Converters
shaped triangular See TPDF
sheath See: jacket.
shelving response Term used to describe a flat (or shelf) end-band shape when applied to program
equalization. Also known as bass and treble tone control responses.
shielding, proper See Steve Macatee's Considerations in Grounding and Shielding and RaneNote: (5 of 19) [10/3/04 12:30:57 AM]
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Sound System Interconnection.
show control See MIDI show control.
SI (International System of Units) The International System of Units, universally abbreviated SI (from
the French Le Système International d'Unités), is the modern metric system of measurement. SI is the
dominant measurement system not only in science, but also in international commerce. See link for a
downloadable copy of Barry N. Taylor's Guide for the Use of the International System of Units (SI). This
free 86 page document is the definitive source of SI info.
sibilant Linguistics. adj. Of, characterized by, or producing a hissing sound like that of (s) or (sh): the
sibilant consonants; a sibilant bird call. A sibilant speech sound, such as English (s), (sh), (z), or (zh).
SID (slew-induced distortion) See: DIM/TIM
side-chain In a signal processing circuit, such as one employing a VCA, a secondary signal path in
parallel with the main signal path in which the condition or parameter of an audio signal that will cause a
processor to begin working is sensed or detected. Typical applications use the side-chain information to
control the gain of a VCA. The circuit may detect level or frequency or both. Devices utilizing sidechains for control generally fall into the classification of dynamic controllers.
sidetone Telephony. The feature of a telephone handset that allows you to hear yourself talk, acting as
feedback that the phone is really working. Sidetones are actually short line echoes bled back into the
earpiece. Too much sidetone sounds like an echo and too little sounds so quiet that people think the
phone is broken. Sidetones are good for people but can cause acoustic feedback in teleconferencing
systems if not treated properly.
sigma-delta See: delta-sigma modulation
signal ground The common electrical reference point of a circuit, usually separate from the chassis
ground but tied together at the power supply. See RaneNote: Sound System Interconnection
signal levels Audio signal levels: see levels.
signal present indicator or SIG PRES An indicator found on pro audio signal processing units that
lights once the input signal level exceeds a preset point. There is no standard specifying when a SIG
PRES light should illuminate, although common practice makes it -20 dBu (77.5 mV), or the pro audio
de facto standard line-level of +4 dBu (1.23 volts). (6 of 19) [10/3/04 12:30:57 AM]
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signal-to-noise ratio See: S/N
SIL (speech interference level) The numerical part of the RC noise rating.
silence Meaning without sound, yet "The Sound of Silence," was a mega hit for Simon and Garfunkel -no zen intended. But the most interesting story about silence is told by David Lister in his article "Big
noises at odds over the sound of silence," reproduced here:
'The Sound of Silence' may have prompted engaging harmonies from Simon and Garfunkel
-- but a more literal appreciation of the absence of noise has prompted one of the more
curious copyright disputes of modern times.
Mike Batt, the man behind the Wombles and Vanessa Mae, has put a silent 60-second track
on the album of his latest classical chart-topping protégés, the Planets. This has enraged
representatives of the avant-garde, experimentalist composer John Cage, who died in
1992. The silence on his group's album clearly sounds uncannily like 4'33", the silence
composed by Cage in his prime.
Batt said last night: "I've received a letter on behalf of John Cage's music publishers. I was
in hysterics when I read their letter.
"As my mother said when I told her, 'which part of the silence are they claiming you
nicked?'. They say they are claiming copyright on a piece of mine called 'One Minute's
Silence' on the Planets' album, which I credit Batt/Cage just for a laugh. But my silence is
original silence, not a quotation from his silence."
Silicon DustTM Nickname for microchips. Trademarked name first coined by National Semiconductor
to describe the world's smallest op amp (as of May 5, 1999), the LMV921. Used in surface mount
technology (SMT), they are about the size of a single letter on this page.
silver One of the English language words without a rhyme -- others are "month," "orange" & "purple."
simplex power Old telephone term for phantom power.
SIN (signal induced noise) Tongue-in-cheek term created by John K. Chester for cable shield induced
noise found when the analog audio cable shield is grounded at one end only.
SINAD (pronounced "sin-add") or S/N+D (signal-to-noise and distortion) Acronym for the ratio: (signal
+ noise + distortion) / (noise + distortion). Or, as Metzler explains, it is the reciprocal of THD+N stated
in decibels (dB). Originally developed for measuring FM receivers, it now also appears on A/D data
sheets. Generally, the term "SINAD" is favored by the communication industry, while the audio industry (7 of 19) [10/3/04 12:30:57 AM]
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used "S/N+D," but they both mean the same thing. It is the preferred way to specify the dynamic range,
or maximum S/N, since the noise and distortion products are measured in the presence of a signal. [A
signal is applied to the input, the output is passed through a notch filter to remove the signal and what
remains is measured. Then the ratio of the rms value of the measured output signal to the rms value of
everything else coming out (i.e., noise + distortion) is expressed in decibels.] This gives a more accurate
picture of real dynamic performance. Sometimes the measurement is stated for three reference levels of 0
dBFS, -20 dBFS, and -60 dBFS.
sine Abbr. sin Mathematics. 1. The ordinate of the endpoint of an arc of a unit circle centered at the
origin of a Cartesian coordinate system, the arc being of length x and measured counterclockwise from
the point (1, 0) if x is positive or clockwise if x is negative. 2. In a right triangle, the ratio of the length of
the side opposite an acute angle to the length of the hypotenuse. (AHD)
sine curve Mathematics. The graph of the equation y = sin x. Also called sinusoid. (AHD)
sine wave Physics. A waveform with deviation that can be graphically expressed as the sine curve.
sine wave speech A term coined by psychologists Robert Remez and David Pisoni to describe their
experiment consisting of synthesizing three simultaneous wavering sine wave tones. The sound was
nothing like speech, yet participants could hear words thus suggesting that the brain can hear speech
content in sounds that do not even resemble speech. [Pinker]
sinusoid Mathematics. See: sine curve
Six Sigma®Abbr. 6s and 6 Sigma In 1986, Bill Smith, a senior engineer and scientist at Motorola,
introduced the concept of Six Sigma® (a registered trademark of Motorola, Inc.) to standardize the way
defects are counted. Simply put, it is a statistical methodology for improving quality control. The Greek
letter "sigma" is used in statistics to represent one standard deviation. This measures how far a given
process deviates from perfection. Six sigma refers to six standard deviations, which equals 99.99985% of
the total (1.5 defects per million). The central idea behind Six Sigma is that if you can measure how
many defects you have in a process, you can systematically figure out how to eliminate them and get as
close to zero defects as possible. However, today six sigma methods foster a huge business in and of
skin effect 1. Electrical cable. The tendency of high frequency (RF and higher) current to be
concentrated at the surface of the conductor. 2. Induction heating. Tendency of an alternating current to
concentrate in the areas of lowest impedance.
slapback See slap echo below. (8 of 19) [10/3/04 12:30:57 AM]
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slap echo also called slapback 1. Acoustics. A single echo resulting from parallel non-absorbing (i.e.,
reflective) walls, characterized by lots of high frequency content. So-called because you can test for slap
echo by sharply clapping your hands and listening for the characteristic sound of the echo in the midrange. Slap echo smears a stereo sound field by destroying the critical phase relationships necessary to
form an accurate sound stage. 2. Recording. Devices that simulate slap echo are popular in recording.
One distinct repeat echo is added to an instrument sound resulting in a very live sound similar to what
you would hear in an auditorium.
slew rate 1. The term used to define the maximum rate of change of an amplifier's output voltage with
respect to its input voltage. In essence, slew rate is a measure of an amplifier's ability to follow its input
signal. It is measured by applying a large amplitude step function (a signal starting at 0 volts and
"instantaneously" jumping to some large level [without overshoot or ringing], creating a step-like look on
an oscilloscope) to the amplifier under test and measuring the slope of the output waveform. For a
"perfect" step input (i.e., one with a rise time at least 100 times faster than the amplifier under test), the
output will not be vertical; it will exhibit a pronounced slope. The slope is caused by the amplifier having
a finite amount of current available to charge and discharge its internal compensation capacitor. 2.
Mathematics. Slew rate is defined to be the maximum derivative of the output voltage with respect to
time. That is, it is a measure of the worst case delta change of voltage over a delta change in time, or the
rate-of-change of the voltage vs. time. For sinusoidal signals (audio), this equals 2 pi times the maximum
frequency, times the maximum peak output voltage: SR = (2 pi) (Fmax) (Vpeak).
slush pump A trombone. (Decharne)
smoke From the phlogiston theory of electronics, it is smoke that makes ICs and transistors work. The
proof of this is self-evident because every time you let the smoke out of an IC or transistor it stops
working -- elementary. This has been verified through exhaustive testing, particularly regarding power
amplifier ICs and transistors. (Incidentally, wires carry smoke from one device to another.) [Origin
unknown but classic.]
smoothing filter See: anti-imaging filter
SMPTE (pronounced "simty") (Society of Motion Picture and Television Engineers) A professional
engineering society that establishes standards, including a time code standard used for synchronization.
SMT (surface mounting technology) The science of attaching and interconnecting electronic devices,
whose entire body projects in front of the mounting surface, as opposed to through-hole devices found on
the earliest printed circuit boards. With surface mount technology all components sit on the surface of
printed circuit boards and are soldered to conductive pads. With through-hole parts, component leads are
placed through holes in the boards and then soldered from the back side. SMT is more cost-effective and
allows far greater density of parts. (9 of 19) [10/3/04 12:30:57 AM]
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S/MUX Abbreviation used for several different things: 1. Sample Multiplexing. Proprietary technology
licensed by Sonorus used to transmit high bandwidth digital audio using existing lower bandwidth
technology. 2. Serial Multiplexer manufactured by MicroRidge. 3. Subtitle Multiplexer manufactured by
S/N or SNR (signal-to-noise ratio) An audio measurement of the residual noise of a unit, stated as the
ratio of signal level (or power) to noise level (or power), normally expressed in decibels. The "signal"
reference level must be stated. Typically this is either the expected nominal operating level, say, +4 dBu
for professional audio, or the maximum output level, usually around +20 dBu. The noise is measured
using a true rms type voltmeter over a specified bandwidth, and sometimes using weighting filters. All
these thing must be stated for a S/N spec to have meaning. Simply saying a unit has a SNR of 90 dB
means nothing, without giving the reference level, measurement bandwidth, and any weighting filers. A
system's maximum S/N is called the dynamic range. See RaneNote: Audio Specifications.
snake or audio snake Live Sound. The nickname for the cable running from the stage of a live
performance to the main mixing console, which is usually set-up in the middle or rear of the audience (in
spite of being called FOH). It typically contains one shielded pair (STP) of wires for each of the stage
microphones. The name comes from the multiconductor cable looking sort of snake-like.
S/N+D or S/(N+D) See SINAD
Snell’s Law States the relationship between the angles of incidence and refraction and the indices of
refraction of any two mediums.
SNMP (Simple Network Management Protocol) The most common method by which network
management applications can query a management agent using a supported MIB (Management
Information Base). SNMP operates at the OSI Application layer. The IP (Internet Protocol)-based SNMP
is the basis of most network management software, to the extent that today the phrase "managed device"
implies SNMP compliance.
snollygoster Defined in 1895 as "a fellow who wants office, regardless of party, platform or principles
and who ... gets there by the sheer force of monumental talknophical assumancy". [McQuain, Never
Enough Words]
Snow, William B. (1903-1968) American engineer best remembered for his foundation work for
stereophonic reproduction in large rooms. See U.S. Patent 2,137,032 Sound Reproducing System. His
paper titled "Basic Principles of Stereophonic Sound," Stereophonic Techniques: An Anthology, edited by
John Eargle (Audio Engineering Society, ISBN 0-937803-08-1, NY, 1986, pp. 9-31) is considered the
best introduction to this subject. Other papers of interest by Snow are collected in Sound Reinforcement:
An Anthology, edited by David L. Klepper (Audio Engineering Society, NY, 1978). His grandson, John (10 of 19) [10/3/04 12:30:57 AM]
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Snow, tells the story of how William used to play binaural wire recordings for them when they were kids,
which he describes as "lots of surreal, cool stuff."
soft clipping See: clipping
solo A term used in recording and live-sound mixing to describe monitoring (via headphones) a single
channel without affecting the main outputs (see: PFL) -- same as cueing; however, it can also refer to
certain console designs where it replaces the main mix with the soloed channel (called destructive solo).
sone A subjective unit of loudness, as perceived by a person with normal hearing, equal to the loudness
of a pure tone having a frequency of 1,000 hertz at 40 decibels sound pressure level. (AHD)
sonofusionName given by inventor Dr. Rusi P. Taleyarkhan, Purdue University physicist, for his cold
fusion experiments combining bursts of ultrasonic high-frequency sound waves with neutron pulses.
sonorous 1. Having or producing sound. 2. Having or producing a full, deep, or rich sound. (AHD)
sound 1.a. Vibrations transmitted through an elastic material or a solid, liquid, or gas, with frequencies in
the approximate range of 20 to 20,000 hertz, capable of being detected by human ears. Sound (in air) at a
particular point is a rapid variation in the air pressure around a steady-state value (atmospheric pressure) that is, sound is a disturbance in the surrounding medium. b. Transmitted vibrations of any frequency. c.
The sensation stimulated in the ears by such vibrations in the air or other medium. d. Such sensations
considered as a group. 2. Auditory material that is recorded, as for a movie. 3. Meaningless noise. 4.
Music. A distinctive style, as of an orchestra or a singer. (AHD) See David Harrison's "Sound". See
RaneNote: Signal Processing Fundamentals. See: velocity of sound.
sound absorption See absorption.
sound occlusion See: occlusion effect.
sound off To express one's views vigorously: He was always sounding off about his boss. (AHD)
sound pressure The value of the rapid variation in air pressure due to a sound wave, measured in
pascals, microbars, or dynes - all used interchangeable, but pascals is now the preferred term.
Instantaneous sound pressure is the peak value of the air pressure, often used in noise control
measurements. Effective sound pressure is the rms value of the instantaneous sound pressure taken at a
point over a period of time.
sound pressure level or SPL 1. The rms sound pressure expressed in dB re 20 microPa (the lowest
threshold of hearing for 1 kHz). [As points of reference, 0 dB-SPL equals the threshold of hearing, while (11 of 19) [10/3/04 12:30:57 AM]
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140 dB-SPL equals irreparable hearing damage.] See: inverse square law 2. Blue whales, the largest
living animals, also make the loudest sounds by any living source. Their low-frequency pulses have been
measured at 188 dB-SPL and detected 530 miles away according to The Guinness Book of World
Sound Recording History Fantastic site put together by David Morton.
sound reinforcement See SR.
SPARS (Society of Professional Audio Recording Services) Founded in 1979, a professional trade
organization that unites the manufacturers of audio recording equipment and providers of services, with
the users. Their goal is worldwide promotion of communication, education and service among all those
who make and use recording equipment. Often confused with NARAS.
spatial Of, relating to, involving, or having the nature of space. (AHD)
Spatializer A single-ended spatial enhancement technique developed by Desper Products, Inc., a
subsidiary of Spatializer Audio Labs, Inc. Widely licensed in both the consumer audio and multimedia
computing markets, the Desper, or Spatializer process is normally used as a postprocessor. The
Spatializer technology manipulates the original signal in a way that causes the listener to perceive a
stereo image beyond the boundaries of the two loudspeakers. It claims to place sounds in front of the
listener in an arc of 180 degrees, with excellent imaging and fidelity.
S/PDIF (Sony/Philips digital interface format, also seen w/o slash as SPDIF) A consumer version of
the AES3 (old AES/EBU) digital audio interconnection standard based on coaxial cable and RCA
connectors. See RaneNote: Interfacing AES3 and S/PDIF.
Speakon® See connectors
spectra A plural of spectrum. In pro audio use, the distribution of frequency of a sound signal,
especially: the distribution of sound energy, arranged in order of frequency wavelengths.
spectrum analyzer Audio Test Equipment. A type of electronic measurement device used to display the
amplitude/frequency components of a continuous signal, as opposed to the amplitude/time domain
oscilloscope. The formal IEEE definitions are "(1) An instrument generally used to display the power
distribution of an incoming signal as a function of frequency. (2) An instrument that measures the power
of a complex signal in many bands. The frequency bands can be either constant absolute bandwidth (e.g.,
FFT analyzer), or constant percentage bandwidth (e.g., RTA analyzer)."
speech intelligibility See STI, RaSTI , ALCONS and STIPA. Also Peter Mapp's overview article (12 of 19) [10/3/04 12:30:57 AM]
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"Measuring Intelligibility" in S&VC magazine.
speech interference level (SIL) The numerical part of the RC noise rating.
speed of sound See: velocity of sound.
spell checker A software program used by word processors to tell you that the following truism has no
spelling errors: "Dew knot trussed yore spell chequer two fined awl mistakes."
SPICE (simulation program with integrated circuit emphasis) A computer circuit analysis program first
developed and written by L. W. Nagel and D. O. Pederson of the EECS (Electrical Engineering and
Computer Sciences) Department of UC Berkeley¹. This was not the first simulation program by members
of UC Berkeley's EECS Department. SPICE evolved from forerunners BIAS² and CANCER³. The
SPICE program was used extensively for classroom instruction and graduate research. As such, each year
it was refined and expanded by each new batch of graduate students (yes, even I worked on SPICE,
helping develop op amp models during my graduate years at UC Berkeley) until it expanded beyond
Berkeley's domain through licensing and the advent of mini and personal computers beginning in 1981.
Indeed, PSPICE (Personal SPICE) developed in 1984 by Wolfram Blume (first doing business as
Blume Engineering, then MicroSim, acquired by OrCAD, now owned by Cadence), the first version of
SPICE for personal computers, is now the industry standard for circuit-simulation.
1. L.W. Nagel and D.O. Pederson, "Simulation Program with Integrated Circuit Emphasis (SPICE),"
presented at the 16th Midwest Symposium on Circuit Theory, Waterloo, Ontario, April 12, 1973.
2. W.J. McCalla and W.G. Howard, Jr., "BIAS-3 -- A Program for the Nonlinear DC analysis of Bipolar
Transistor Circuits," IEEE J. Solid-State Circuits, vol. SC-6, Feb. 1971, PP. 14-19.
3. L. Nagel and R. Rohrer, "Computer Analysis of Nonlinear Circuits, Excluding Radiation (CANCER),"
IEEE J. Solid-State Circuits, vol. SC-6, Aug. 1971, pp. 166-182.
spider Loudspeakers. The assembly which holds the voice coil of a dynamic loudspeaker centered in the
magnetic gap. The spider is a corrugated circular piece of specially treated fabric. The name comes from
the early days of loudspeakers when it was made of a plastic material that resembled the legs of a spider.
SPIF (sales promotion incentive fund) Same as no. 3 following.
spiff 1. To make attractive, stylish, or up-to-date: spiffed up the old storefront. 2. Attractiveness or charm
in appearance, dress, or manners: "He may need more than spiff to get him through the bad patches
ahead" James Wolcott [Possibly from dialectal spiff well-dressed] (AHD) 3. Giveaways (usually in the
form of money) by manufacturers as added incentive ("make attractive") to personnel selling their goods.
Compare with swag (13 of 19) [10/3/04 12:30:57 AM]
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spiral quad Same as star quad; see cables.
SPL controller See: leveler
SPL See: sound pressure level
splitter An audio device used to divide one input signal into two or more outputs. Typically this type of
unit has one input with 6-16 (or more) outputs, each with a level control and often is unbalanced. See:
distribution amplifier
spooler Comes from the acronym SPOOL derived from simultaneous peripheral operation on-line (also
sequential peripheral operations on-line). A program or piece of hardware that controls a buffer of data
going to some output device, including a printer or a screen. Spooling temporarily stores programs or
program outputs on magnetic tape, RAM or disks for output or processing. (Newton) ... and you thought
you were done learning for the day -- Ha!
SR (sound reinforcement) See Bruce Borgerson excellent S&VC article on P.A. vs. SR.
SQ Columbia's (CBS - now Sony Music) name for their quadraphonic sound system using a proprietary
matrixing algorithm for encoding four-channel sound down to two-channels. See Matrix Quad Compare
with QS
SQNR (signal to quantization noise ratio A measure of the quality of the quantization, or digital
conversion of an analog signal. Defined as normalized signal power divided by normalized quantization
noise power. The SQNR in dB is approximately equal to 6 times the number of bits of the ADC, for
example, the maximum SQNR for 16 bits is approximately 96 dB.
square wave A periodic waveform characterized by a 50% duty cycle and a Fourier series consisting of
odd-ordered, equal phase, sinusoidal harmonic components of its fundamental frequency with amplitudes
(coefficients multiplying the magnitude of the fundamental sine wave) equal to 1/n, where n equals the
harmonic number. Therefore the first few harmonic amplitudes are 1/3, 1/5, 1/7, 1/9, etc. For a very cool
pictorial, see Fourier Series: Square Wave Tool. And if you are missing the math, see Cuthbert Nyack's
Fourier Series of Square Wave
SRS (Sound Retrieval System) A stereo image enhancement scheme invented by Arnold Klayman in the
early '80s while working for Hughes Aircraft, and since 1993, marketed by SRS Labs, Inc. A standalone
spatial enhancement scheme, SRS benefits from not requiring encoding of the signal, but thus prevents
the audio producer from determining the location of individual sound effects. The results vary, being
heavily dependent upon the original stereo mix. The goal is to extend the sound field well beyond the
limitations of the loudspeakers, and make the overall sound seem more expansive. The elimination of the (14 of 19) [10/3/04 12:30:57 AM]
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sweet spot is claimed.
state-variable filter An electronic filter based on state-variable techniques, first described by W. J.
Kerwin, L. P. Huelsman, and R. W. Newcomb, "State variable synthesis for insensitive integrated circuit
transfer functions," IEEE J. Solid Circuits, vol. SC-2, pp. 87-92, Sept. 1967. State-variable filters are also
known as KHN filters in their honor. The concept of state-variable is one where a single variable
defines one of the characteristics (or states) of a filter (e.g., the gain, or the center/corner frequency, or
the Q). The state-variable approach yields independent adjustment of the transfer function pole and zero
locations. [The transfer function is a Laplace transform equation of the output divided by the input
consisting of the ratio of two polynomials. Poles and zeros are the mathematical names for the solutions
of the numerator polynomial -- called zeros because they cause the numerator to have zero value -- and
denominator polynomial -- called poles because they cause the denominator to have zero value which
makes the ratio infinity.] This desirable independent adjustment feature allows the design of parametric
EQs with independent adjustment of all three filter parameters, or constant-Q graphic EQs with
amplitude-bandwidth independence (See RaneNote: Constant-Q Graphic Equalizers), or simultaneous
low-pass and high-pass active crossovers (See RaneNote: Linkwitz-Riley Crossovers). The state-variable
topologies also have lower component sensitivities that other designs, thus producing more productionfriendly products. Most commonly seen with three op amps, they may be constructed using from one to
four op amps.
standing wave See room mode.
star quad mic cable See cables.
Star-Spangled Banner The flag of the United States.
star topology 1. A set of three or more branches with one terminal of each connected at a common node.
2. A communications network based on a star pattern where all equipment is connected to a central
location with a single path.
star-wired ring See token ring.
steganography The science of communicating in a way that hides the existence of the actual
communication. The practice of hiding information in a wider bandwidth carrier. This field covers the
techniques used in digital watermarking schemes.
Steinweiss, Alex (1916- ) The father of the album cover, he designed the first album cover in 1939 for
Columbia Records where he worked as their first art director.
stereo or stereophonic sound 1. "The word stereophonics was derived by combining two Greek words:
stereo, which means solid and implicates the three spatial dimensions (depth, breadth, and height), and (15 of 19) [10/3/04 12:30:57 AM]
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phonics, which means the science of sound. Thus, stereophonics denotes the science of 3-dimensional
sound" [Streicher & Everest]. 2. Term applied to any system of recording (or transmission) using
multiple microphones for capturing and multiple loudspeakers for reproduction the sound. Stereo as the
term has become popularly used restricts the number of playback loudspeakers to two, but strictly
speaking the term can apply to any number of loudspeakers. Although stereo was first demonstrated at
the Paris Opera in 1881 (really) using carbon microphones and earphones, it would not become
widespread until the work of Blumlein in the 1930s. Also see William B. Snow.
stereo 2-way or stereo 3-way, etc. See: active crossover
stewardesses Longest English word typed using only the left hand.
STI (speech transmission index) See RASTI.
STIPa (speech transmission index for public address systems) A speech intelligibility measurement
described by developers H. Steeneken, J. Verhave, S. McManus and K. Jacob in their paper
"Development of an Accurate, Handheld Simple-to-Use, Meter for the Prediction of Speech
Intelligibility," Proc. IOA, Vol. 23, Pt. 8, 2001. Goldline manufactures a model. Equivalent British term
is PASTI for public address STI.
stiction Physics. In positioning, the friction that prevents immediate motion when force is first applied to
a body or surface at rest.
Stockham, Jr., Thomas G. (1934-2004) American electrical engineer best known for his pioneering
work in digital audio recording and editing. Known as the father of digital magnetic sound recording, Dr.
Stockard earned Grammy, Emmy and Academy awards for his work and was the founder of
Soundstream, Inc.
stopband The range of frequencies substantially attenuated by a filter as opposed to the range of
frequencies unaffected by the filter. The opposite of passband.
STP (shielded twisted-pair) See cables; also Scientifically Treated Petroleum, but that's another story
from another time.
streaming media Internet. A process in which audio, video, and other multimedia is delivered “just in
time” over the Internet or company intranet. Pioneered and named by Netscape, as a smarter way to
deliver data, their browser immediately loaded text and then followed with graphics in real time as it
arrived (streamed in), then RealNetworks came along and applied this technology to audio and video.
structured audio See MPEG-4 (16 of 19) [10/3/04 12:30:57 AM]
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Studio 54(1977-1979: dates for the original club) Famous disco club located in an old CBS TV studio
located at 254 West 54th Street, Manhattan, NY -- hence, the name.
subcardiod microphone See: cardiod microphone.
subcode Non-audio digital data encoded on a CD that contains definable information such as track
number, times, copy inhibit, copyright, etc.
subgroups See: groups
submix See: groups
subsonic Having a speed less than that of sound in a designated medium. (AHD) [Use infrasonic if
referring to frequencies below human hearing range.]
subtend 1. Mathematics. To be opposite to and delimit: The side of a triangle subtends the opposite
angle. 2. To underlie so as to enclose or surround: flowers subtended by leafy bracts. [AHD]
subwoofer A large woofer loudspeaker designed to reproduce audio's very bottom-end, i.e.,
approximately the last one or two octaves, from 20 Hz to 80-100 Hz. [Actually misnamed since subsonic
means slower than audio, while infrasonic means lower than audio, it should be called an
"infrawoofer."] See Royal Device for the ultimate subwoofer.
successive approximation Early method of A/D conversion. For a detailed example see RaneNote:
Digital Dharma of Audio A/D Converters
supra-aural Headphones. Literally "on the ear," thus headphones with earpieces resting on the ear.
Comfortable to wear but the lack of a tight seal allows lots of ambient noise -- sometimes this is desired;
sometimes it is not. Compare with: circumaural.
supersonic Having, caused by, or relating to a speed greater than the speed of sound in a given medium,
especially air. (AHD) [Use ultrasonic if referring to frequencies above human hearing range.]
suppression also gain suppression In teleconferencing the term used to describe the technique of
instantaneous reduction of a sound system's overall gain to control acoustic feedback, and thus reduce
surface transfer impedance See: ZT (17 of 19) [10/3/04 12:30:57 AM]
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surround Loudspeakers. The circular ring mechanism that attaches the cone to the frame ("surrounding"
the cone), usually rolled (allows greater throw) and made from foam or rubber material.
surround sound Generic term for sound systems using more than mono (one front channel), or stereo
(two left-right channels) loudspeakers to create a two- or three-dimensional experience. For examples see
5.1 surround sound and Ambisonics.
sustain Music. A prolonged note, especially the ability to maintain a note beyond its natural decay.
Electric guitarists produce this effect by leaning toward their amplifier loudspeaker causing the signal to
feed back into the pick-up. In popular music, most famously used by Carlos Santana, Jimi Hendrix and
Gabor Szabo.
S-video Also called Y/C video, a two-channel video channel that transmits black and white, or luminance
(Y), and color portions, or chrominance (C), separately using multiple wires. This avoids composite
video encoding, such as NTSC, thus providing better picture quality. Found mostly on S-VHS and Hi8
products, and some Laserdisc and DVD players.
swag 1. Slang Stolen property; loot. [According to Mercenary Audio: (pirate term) Stolen without a gun,
but I can find no collaboration.] 2. Slang Herbal tea in a plastic sandwich bag sold as marijuana to an
unsuspecting customer. 3. Australian To travel about with a pack or swag. (AHD) 4. Slang Acronym for
scientific (or silly or sophisticated) wild ass guess. 5. Slang Giveaways (usually in the form of
merchandise "loot") by manufacturers as added incentive to personnel either selling or buying their
goods. Compare with spiff
sweet spot Any location in a two-loudspeaker stereo playback system where the listener is positioned
equidistant from each loudspeaker. The apex of all possible isosceles (two equal sides) triangles formed
by the loudspeakers and the listener. In this sense, the sweet spot lies anywhere on the sweet plane
extending forward from the midpoint between the speakers.
SWG (standard wire gauge) British or Imperial standard. See AWG.
symmetrical (reciprocal) response Term used to describe the comparative shapes of the boost/cut
curves for variable equalizers. The cut curve exactly mirrors the boost curve.
synchronous A transmission process where the bit rate of the signal is fixed and synchronized to a
master clock.
Syn-Aud-Con (Synergetic Audio Concepts) A private organization conducting audio seminars and
workshops, sponsored by several pro audio companies. (18 of 19) [10/3/04 12:30:57 AM]
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| 0-9 | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | Top |
Copyright Rane Corporation. All rights reserved. (19 of 19) [10/3/04 12:30:57 AM]
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Pro Audio Reference
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3-dB down point See: passband
3D sound A term used to describe a three-dimensional sound field. A true 3D sound field positions
sound anywhere in a semi-spherical shell surrounding the listener. Sound must come from anywhere
directly behind to directly overhead to directly in front of the listener and all points left and right. It if
does not, it is not 3D sound. The term is popularly misused by multimedia companies to describe
systems, effects and techniques purported to create 3D sound from two sources and designed for twoloudspeaker playback; however, the result is not 3D sound. It is enhanced two-dimensional sound.
Strictly speaking, a broadening, widening, enhancing, or spreading of the left/right sound stage is not 3D.
No two-loudspeaker system is capable of locating sounds directly to the rear of the listener; nevertheless,
some of these systems truly impress. The best enhancement schemes come very close to recreating a
quarter-spherical sound shell, extending to nearly 180 degrees left-to-right, approaching 90 degrees
overhead, with greatly improved depth of field. For further information see the Ultimate Spatial Audio
Index, and Links to the World of Spatial Sound.
10Base-T See: Ethernet
21-gun salute Among the many "true origins," this is my favorite: A tribute for dignitaries created by
Francis Hopkinson, a signer of the Declaration of Independence, and the designer of the first Stars and
Stripes flag. As for the creation of the 21-gun salute, the story goes ...
Hopkinson was fond of doodling. As he sat in meetings during the momentous days as the
Colonies debated the merits of independence from England, he wrote, over and over, the
year: "1776." Idly adding up the numbers 1, 7, 7, and 6, the total, 21, intrigued him. Why
not institute a 21-gun salute for dignitaries of the new republic? He submitted his idea to
Congress, and it has been in use ever since. [Bartlett's Book of Anecdotes]
T-1 (trunk level 1) A digital transmission scheme utilizing two twisted-pair capable of handling a
minimum of 24 voice channels. Used for connecting networks across remote distances. (Newton)
talent cueing See IFB
talkback 1. A recording console feature where a microphone mounted on the console allows the (1 of 12) [10/3/04 12:31:05 AM]
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engineer to speak with the musicians during sessions -- a very useful feature when the console is located
in a soundproof control room, or out in the audience for sound reinforcement systems. 2. A proposed
Rane product line aimed at the coffin market, since abandoned.
talk box A poor man's vocoder. Popularized by Peter Frampton and Joe Walsh in the '70s. See Heil Talk
talkover A term and function found on DJ mixers allowing the DJ to speak over the program material by
triggering a ducker. Compare with voiceover.
taper See potentiometer
tapir Any of several large, chiefly nocturnal, odd-toed ungulates (hoofed mammals) of the genus Tapirus
of tropical America, the Malay Peninsula, and Sumatra, related to the horse and the rhinoceros, and
having a heavy body, short legs, and a long, fleshy, flexible upper lip. (AHD) [Don't confuse with "taper"
taste test or tongue test An actual voltage testing method recommended by Terrell Croft in his book The
American Electricians' Handbook, published by McGraw-Hill in 1913. Here's the passage found on page
"The presence of low voltages can be determined by 'tasting.' The method is feasible only
where the pressure is but a few volts and hence is used only in bell and signal work. Where
the voltage is very low, the bared ends of the conductors constituting the two sides of the
circuit are held a short distance apart on the tongue. If voltage is present a peculiar mildly
burning sensation results which will never be forgotten after one has experienced it. The
'taste' is due to the electrolytic decomposition of the liquids on the tongue which produces
a salt having a taste. With relatively high voltages, possible 4 or 5 volts, due to as many
cells of battery, it is best to first test for the presence of voltage by holding one of the bared
conductors in the hand and touching the other to the tongue. Where a terminal of the
battery is grounded, often a taste can be detected by standing on moist ground and
touching a conductor from the other terminal to the tongue. Care should be exercised to
prevent the two conductor ends from touching each other at the tongue, for if they do a
spark can result that may burn."
And from the same book comes these words of wisdom for testing for the presence of
electricity by touching the two conductors:
"Electricians often test circuits for the presence of voltage by touching the conductors with
the fingers. This method is safe where the voltage does not exceed 250 and is often very
convenient for locating a blown-out fuse or for ascertaining whether or not a circuit is (2 of 12) [10/3/04 12:31:05 AM]
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alive. Some men can endure the electric shock that results without discomfort whereas
others cannot. Therefore, the method is not feasible in some cases."
[We don't know how Mr. Croft died, but perhaps we could hazard a guess. Thanks RH.]
tau Mathematics. In professional mathematical literature the symbol for the Golden Ratio, or Golden
Rectangle, but now phi is the more common symbol.
taut-band Electrical meter mechanism. Consisting of a permanent magnet and moving coil.
Favored for its friction free suspension, allowing precision measurements.
Tchebysheff or Tschebyscheff See: Chebyshev
tchotchke See chachka
TCP/IP (transmission control protocol/internet protocol) A set of protocols developed by the
Department of Defense in the '70s to link dissimilar computers across many kinds of networks and
LANs. Popular with Ethernet users.
TDIF (Teac digital interface format) Tascam's (Teac) 8-channel digital audio interface to their DA-88
digital multitrack recorder, using unbalanced signal transmission and a DB-25 type connector.
TDM (time division multiplexing) Data Transmission. A transmission interleaving technique where
multiple sources, say, data, voice and video, are broken up into pieces and each piece is assigned a
unique time slot with no overlap between pieces. This allows simultaneous transmission of multiple
signals over a common path.
TDS (time-delay spectrometry) A sound measurement theory and technique developed in 1967 by
Richard C. Heyser (1931-1987) at the Jet Propulsion Laboratories of the California Institute of
Technology. For a detailed introduction to the theory and practice of TDS see Time Delay Spectrometry:
An Anthology of the Works of Richard C. Heyser on Measurement Analysis and Perception by John
TEF (time-energy-frequency) The term adopted to describe the entire spectrum of TDS measurements,
including energy-time curves. Popularized by Richard Heyser through his participation in Synergetic
Audio Concepts seminars. Made practical in 1979 by the Techron division of Crown International - Cal
Tech's first TDS licensee, and introduced as the TEF System 10.
tele- Distance; distant: telescope. [Greek tele- meaning far off.] (AHD) (3 of 12) [10/3/04 12:31:05 AM]
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telecommunication Communicating over a distance by wire, fiber or wireless means.
teleconferencing An audio conference held by three or more persons over a distance. Normal usage
refers to voice conferencing, also termed audioconferencing that includes all forms of audio. The term is
sometimes extended to include video and document, or data, conferencing. Note that the term does not
mean telephone conferencing, but rather distance conferencing, although telephone lines are often used.
[Thanks to RG at Q Factor for pointing out this important distinction.] Contrast with videoconferencing.
telemedicine A specialized form of videoconferencing optimized for medical uses. Also referred to as
medical conferencing, it allows distance learning in medical education and delivers health care (including
assisted medical operations) to patients and providers at a distance.
Telharmonium Invented and patented (US patent #580,035) by Thaddeus Cahill, in the 1890s, an
amazing monstrosity weighing 7 tons that was the first device to successfully send music through a
telephone connected to something similar to a gramophone cone that could be heard by an audience.
Arguably the beginning of background music and synthesizers.
temperament Music. The building up of musical scales.
tempo Music. The speed at which music is or ought to be played, often indicated on written
compositions by a descriptive or metronomic direction to the performer. (AHD)
temporal Of, relating to, or limited by time. (AHD)
temporal masking A specific kind of masking where time separates arriving signals.
Masking of a later arriving signal due to an earlier one is called forward masking. The
effects of a loud first sound can last long enough to mask a later arriving softer one
(periods less than 500 ms and greater than 10 dB loudness differences).
The opposite effect where an earlier sound is masked by a later arriving one is called
backward masking, i.e., the second arriving event covers up the first arriving signal. This
is only possible because the ear requires time to form an echoic image before it is
processed by the central nervous system. If a later sound is much louder it can take
precedence over an earlier arriving one (within about 100 to 200 ms).
terminal strips See connectors.
Tesla, Nikola (1856-1943) Serbian-born American electrical engineer and physicist who discovered the
principles of alternating current (1881) and invented numerous devices and procedures that were seminal (4 of 12) [10/3/04 12:31:05 AM]
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to the development of radio and the harnessing of electricity. (AHD)
tetrode A type of vacuum tube having two grids, where one is used to reduce feedback related
instabilities and oscillations. A tetrode has four elements: plate, cathode, control grid and screen grid.
thaumaturgy The working of miracles or magic feats, like designing and building a 24-bit audio
converter that actually measures 144 dB dynamic range.
THD (third-harmonic distortion) See third-harmonic distortion
THD (total harmonic distortion) A measurement technique rarely used, but often confused with the
THD+N technique described below. Many people mistakenly refer to a "THD" measurement when they
really mean the "THD+N" technique. [For completeness and the abnormally curious: a true THD
measurement consists of a computation from a series of individual harmonic amplitude measurements,
rather than a single measurement. "THD" is the square root of the sum of the squares of the individual
harmonic amplitudes. And the answer must specify the highest order harmonic included in the
computations; for example, "THD through 8th harmonic." (from Metzler)] See RaneNote: Audio
THD+N (total harmonic distortion plus noise) The most common audio measurement. A single sine
wave frequency of known harmonic purity is passed through the unit under test, and then patched back
into the distortion measuring instrument. A measurement level is set; the instrument notches out the
frequency used for the test, and passes the result through a set of band-limiting filters, adjusted for the
bandwidth of interest (usually 20-20 kHz). What remains is noise (including any AC line [mains] hum or
interference buzzes, etc.) and all harmonics generated by the unit. This composite signal is measured
using a true rms detector voltmeter, and the results displayed. Often a resultant curve is created by
stepping through each frequency from 20 Hz to 20 kHz, at some specified level (often +4 dBu), and
bandwidth (usually 20 kHz; sometimes 80 kHz, which allows measurement of any 20 kHz early
harmonics). [Note that the often-seen statement: "THD+N is x%," is meaningless. For a THD+N spec to
be complete, it must state the frequency, level, and measurement bandwidth.] While THD+N is the most
common audio test measurement, it is not the most useful indicator of a unit's performance. What it tells
the user about hum, noise and interference is useful; however that information is better conveyed by the
signal-to-noise (S/N) ratio specification. What it tells the user about harmonic distortion is not terribly
relevant simply because it is harmonically related to the fundamental, thus the distortion products tend to
get masked by the complex audio material. The various intermodulation (IM) distortion tests are better
indicators of sonic purity. See RaneNote: Audio Specifications
thermal noise See: Johnson noise
theremin Considered the first electronic musical instrument, invented in 1919 by Russian born Lev
Sergeivitch Termen, which he anglicized to Leon Theremin. The theremin is unique in that it is the only (5 of 12) [10/3/04 12:31:05 AM]
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musical instrument played without being touched. Interestingly, when granted a US Patent in 1928, there
were 32 prior patents referenced, going all the way back to Lee De Forest. A theremin works by causing
two oscillators to "beat" together. The beat frequency equals the difference in frequency between the two
signals. Beats are a physical phenomenon occurring in the air when sounds are mixed. A theremin uses
one oscillator operating well above the upper limit of human hearing as a reference tone, and another
oscillator whose frequency is varied by the proximity of a human hand, for instance, to a capacitive
sensing element shaped like an antenna. A typical machine has two antennas and you play it by moving
your hands nearer to and farther from the antennas. One antenna controls the volume of the sound, while
the other controls the frequency, or pitch, of the sound. Used together you can creates sounds that can
range from being very sci-fi-ish -- a sort of quivering sound -- as heard in early sci-fi movies like The
Day the Earth Stood Still, to very complex jazz licks. The theremin even appears as Dr. Hannibal Lecter's
favorite instrument in Thomas Harris' bestseller Hannibal (Delacorte, 1999).
It was the theremin that got Bob Moog (inventor of the Moog Synthesizer and considered the father of
modern electronic music) interested in electronic music. His latest company Big Briar now makes some
of the world's best theremins.
See the Theremin web ring for additional info; and to view the fascinating, bizarre, and stranger-thanfiction true-life story of Leon Theremin, check out the film (available on video), Theremin: An
Electronic Odyssey, by Steven M. Martin (1994), including several performances by Clara Rockmore,
perhaps the best theremin player ever.
thermionic valve See vacuum tube and Fleming
third-harmonic distortion The standard test used on analog magnetic tape recorders to determine the
maximum output level (MOL), which was defined to occur at the magnetization level at which a
recorded 1 kHz sine wave reached "3 percent third-harmonic distortion." Of course, third-harmonic
distortion is nothing more than a measurement of the amplitude of the third harmonic of the input
frequency and is the most prominent distortion component in analog magnetic recording systems. The
third-harmonic level was used as a convenient figure-of-merit because the 2nd harmonic is difficult to
hear, since it tends to reinforce the pitch of the fundamental. The 3rd harmonic is easy to detect on pure
tones (although less so on music), thus it makes a good benchmark for comparing sound "off tape" with
the original. The distorted tone has an edge to it, containing a component one octave and a quint (interval
of a fifth in music) above the fundamental. For this reason the third-harmonic is also called a musical
twelfth. Here's the interesting twist. This test was commonly abbreviated and listed on the specification
sheet as "THD". Which, of course, was mistaken to mean "total harmonic distortion" instead of "third
harmonic distortion." This led to it being mistakenly shortened to just "distortion," so you still find old
analog tape date sheets, and many text books defining MOL as the point at which there exist "3%
distortion," instead of the correct reference to "3% third-harmonic distortion" -- quite different things.
third-octave Term referring to frequencies spaced every three octaves apart. For example, the thirdoctave above 1 kHz is 8 kHz. Commonly misused to mean one-third octave. While it can be argued that (6 of 12) [10/3/04 12:31:05 AM]
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"third" can also mean one of three equal parts, and as such might be used to correctly describe one part of
an octave split into three equal parts, it is potentially too confusing. The preferred term is one-third
Thompson filters See: Bessel crossover
THX® Ltd. (formerly a division of Lucasfilm Ltd.) term meaning several things: 1) THX Digital
Cinema: audio playback design and certification program for commercial cinema theaters; 2) THX
Cinema: audio playback specification for home cinema systems; 3) THX Home: approved audio/video
playback equipment meeting their standards of quality and performance, as well as DVDs, laserdiscs and
VHS tapes mastered by them to meet their quality and performance standards. New categories are THX
Mobile and THX Games. The term comes from two sources: George Lucas's first film THX-1138
(student version; commercial version), and a somewhat tongue-in-cheek reference to Tomlinson
Holman's eXperiment, after their original technical director, patentee and creative force behind all the
above (who now runs TMH Corporation). See RaneNote: Home Cinema Systems
THX Surround EX Surround-sound format that matrix-encodes a third surround channel into the
existing left and right surround channels in a Dolby Digital signal. This channel drives a center rear
loudspeaker. Compare with DTS-ES.
TIA (Telecommunications Industry Association) Created in 1988 by a merger of the US
Telecommunications Suppliers Association (USTSA) and the EIA's Information and
Telecommunications Technologies Group (EIA/ITG). This organization works with the EIA in
developing technical standards and collecting market data for the telecommunication industry.
Tice Clock An overt act of fraud perpetrated on the audio ignorant who suffer from acute aural
hallucinations and beg to be separated from their money. See Bob Pease's wonderful "What's All This
Hoax Stuff, Anyhow?"
tiger A great cat whose skin is striped, not just his fur.
TIM (transient intermodulation distortion) See: IM
timbre (pronounced "tambur") 1. The quality of a sound that distinguishes it from other sounds of the
same pitch and volume. (AHD) 2. Music. The distinctive tone of an instrument or a singing voice.
time 1.a. A nonspatial continuum in which events occur in apparently irreversible succession from the
past through the present to the future. b. An interval separating two points on this continuum. c. A
number, as of years, days, or minutes, representing such an interval. d. A similar number representing a
specific point on this continuum, reckoned in hours and minutes. 2. Music. a. The characteristic beat of (7 of 12) [10/3/04 12:31:05 AM]
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musical rhythm: three-quarter time. b. The speed at which a piece of music is played; the tempo. (AHD)
[Time is nothing more than a relationship between moving objects. Stop all movement and you stop time.
An important concept in understanding just what time is, lies in understanding that time is in the
universe; the universe is not in time. Which explains why it is not a valid question to ask, "How old is the
universe?" The universe does not have an age; it is not in relationship with another moving object; it is
not in time.] ["Time is what keeps everything from happening all at once." unknown source]
time code or timecode 1. General. A sequence of discrete numeric codes occurring at regular intervals
used to determine time. Various time code formats and methods exist. The following are the most
popular pro audio applications. 2. SMPTE/EBU. A standardized 80-frame word embedded as part of
motion picture or sound recording (standardized for recording by SPARS). A specific identity or address
is assigned to each moment of time in a recording, broken down into
HOURS:MINUTES:SECONDS:FRAMES. 2. MIDI. MIDI time code (MTC), is used to synchronize
MIDI systems with the rest of the audio and video world. 3. AES3 or AES/EBU. Within this standardized
digital audio serial interface are provisions for time data. 4. Additional recording time code methods are
Linear or Longitudinal Time Code (LTC), Vertical Interval Time Code (VITC), Burnt-In or Burned In
Time Code. 5. Time codes for purposes other than video and audio production include Inter-range
instrumentation group (IRIG), Global Positioning System (GPS), Network Time Protocol (NTP), and
Radio Clocks.
time delay No such thing; a misnomer. You cannot delay time (see above). Misused to mean signal
delay or just delay.
tin-pan (tinny piano) From the cheap pianos associated with music publishers' offices that sounded like
banging on tin pans. In the mid-1880s, gave birth to the name Tin Pan Alley, a district (West 28th St. in
Manhattan) associated with musicians, composers, and publishers of popular music, or the publishers
and composers of popular music considered as a group.
toeology Tap dancing. (Decharne)
token ring A LAN baseband network access mechanism and topology in which a supervisory "token" (a
continuously repeating frame [group of data bits] transmitted onto the network by the controlling
computer; it polls for network transmissions) is passed from station to station in sequential order.
Stations wishing to gain access to the network must wait for the token to arrive before transmitting data.
In a token ring topology, the next logical station receiving the token is also the nest physical station on
the ring. This mechanism prevents collisions on this type of network. Normally connected as a star-wired
ring where each station is wired back to a central point known as the multistation access unit (MAU).
The MAU forms a ring of the devices and performs the back-up function of restoring the ring should one
of the devices crash or lose its cable connection.
tone 1. Music. a. A sound of distinct pitch, quality, and duration; a note. b. The interval of a major (8 of 12) [10/3/04 12:31:05 AM]
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second in the diatonic scale; a whole step. c. A recitational melody in a Gregorian chant. 2.a. The quality
or character of sound. b. The characteristic quality or timbre of a particular instrument or voice. (AHD)
tone controls The term most often referring to a two-band shelving equalizer offering amplitude control
only over the highest (treble, from music, meaning the highest part, voice, instrument, or range)
frequencies, and the lowest (bass, from music, meaning the lowest musical part) frequencies. Sometimes
a third band is provided for boost/cut control of the midband frequencies. See also: Baxandall tone
tonic Music. Of or based on the keynote. (AHD)
topology Electronics. The interconnection pattern of nodes on a network. The logical and/or physical
arrangement of stations on a network (e.g., star topology; tree topology; ring topology; bus topology,
etc.). The geometric pattern or configuration of intelligent devices and how they are linked together for
communications. (IEEE) Mathematics. "The branch of geometry concerned only with those basic
properties of geometric figures that remain unchanged when the figures are twisted and distorted,
stretched and shrunk, subjected to any 'schmooshing' at all as long as they're not ripped or torn. Size and
shape are not topological properties since clay balls, dice, and oranges, for example, can be contracted,
expanded or transformed into one another without ripping." (Who's Counting?, John Allen Paulos)
toroid The name for any doughnut-shaped body. [Mathematics: a surface generated by a closed curve
rotating about, but not intersecting or containing, an axis in its own plane. [AHD] The shortened popular
name for the doughnut-shaped (toroidal) transformers common to audio equipment; favored for their low
hum fields.
TOSLINK (Toshiba link) A popular consumer equipment fiber optic interface based upon the S/PDIF
protocol, using an implementation first developed by Toshiba.
total harmonic distortion See THD and THD+N
T-pad See attenuator pad.
TPDF (triangular probability density function) Also called triangular dither. The most popular form of
dither signal, described in detail in the landmark paper by Stanley Lipshitz, Robert Wannamaker, and
John Vanderkooy, "Quantization and Dither: A Theoretical Survey," published in the J. Audio Eng. Soc.,
Vol. 40, No. 5, 1992, pp. 355-375 (issue available from the AES, but only recommended for the
mathematically needy). As the name implies, TPDF describes a probability density function shaped like a
triangle, instead of the more often seen bell-shaped curve. For dither use, the extremes represent the
maximum possible quantization error of ±1 LSB. Also very popular is a variant known as shaped
triangular or high-passed TPDF, which is essentially high-pass filtered triangular dither that places (9 of 12) [10/3/04 12:31:05 AM]
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most of the dither energy at higher frequencies making it less audible.
tracking power amplifiers A term used to describe audio power amplifier designs utilizing a variable
power supply for the output, and a means of controlling the power supply based upon the input signal.
This scheme improves efficiency. See: Class H Amplifiers and compare with rail-switchers.
trademarks See: USPTO.
Traf-O-Data See: Microsoft
transcendental number Mathematics. 1. Not capable of being determined by any combination of a
finite number of equations with rational integral coefficients. 2. Not expressible as an integer or as the
root or quotient of integers. Used of numbers, especially nonrepeating infinite decimals. (AHD)
transducer Electrical. A device, such as a microphone, or loudspeaker, that converts input energy of one
form into output energy of another.
transfer function Electronic circuits. For a linear system, the ratio of the LaPlace Transform of the
output to that of the input with no other input signals and initial conditions zero.
transform switch Turntablist mixers. This switch selects either phono or line as the channel source, but
is commonly used for transforming, or quickly gating the source on and off.
transient response The reaction of an electronic circuit, or electromechanical device, or acoustic space
to a non-repetitive stimulus such as a step or impulse response. It is the result to a sudden change in the
input that is nonperiodic. For example, percussive instruments produce primarily transient sounds. The
transient stimulus and resulting response are characterized by the amplitude and the rise time (and fall
time if it is an impulse), overshoot, and settling time. The standard reference is to note the maximum
amplitude and the time required to reach within 10% of the steady-state value. For a real world example
of the comparative transient responses for a full-range and a 3-way loudspeaker system, see Siegfried
Linkwitz's Group delay and transient response ; also see group delay
transonic Acoustics. Of or relating to aerodynamic flow or flight conditions at speeds near the speed of
sound. [AHD]
transversal equalizer A multi-band variable equalizer using a tapped audio delay line as the frequency
selective element, as opposed to bandpass filters built from inductors (real or synthetic) and capacitors.
The term "transversal filter" does not mean "digital filter." It is the entire family of filter functions done
by means of a tapped delay line. There exists a class of digital filters realized as transversal filters, using
a shift register rather than an analog delay line, with the inputs being numbers rather than analog
functions. (10 of 12) [10/3/04 12:31:05 AM]
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traveling wave Something vibrating creates a wave pattern that travels through a medium from one
place to another.
tree topology A LAN topology that recognizes only one route between two nodes on the network. The
map resembles a tree or the letter T.
tremolo 1. A tremulous effect produced by rapid repetition of a single tone. A similar effect produced by
rapid alternation of two tones. 2. A device on an organ for producing a tremulous effect. 3. A vibrato in
singing, often excessive or poorly controlled. [AHD]
triamp, triamplified, or triamplification Term used to refer to a 3-way active crossover where the
audio signal is split into three paths, and using separate power amplifier channels for each driver.
triangle wave A periodic waveform characterized by a 50% duty cycle and a Fourier series consisting of
odd-ordered, equal phase, sinusoidal harmonic components of its fundamental frequency with amplitudes
(coefficients multiplying the magnitude of the fundamental sine wave) equal to 1/n&#178, where n
equals the harmonic number. Therefore the first few harmonic amplitudes are 1/9, 1/25, 1/49, 1/81, etc.
For a very cool pictorial, see Fourier Series: Triangle Wave Tool. And if you are missing the math, see
Cuthbert Nyack's Fourier Series of Triangle Wave
triangular dither See TPDF
triple point of water A system is at the "triple point" when ice (solid), water (liquid), and vapor (gas)
coexist in equilibrium. This point is the freezing point of water and is set by international agreement to
equal 273.16 kelvin (0 degrees Celsius; 32 degrees Fahrenheit)
trottery Dancehall. (Decharne)
troxelator See: feedback troxelator
true response graphic equalizer A graphic equalizer whose output characteristics perfectly match the
position of the front-panel slide controls. Contrast with proportional-Q and constant-Q designs. See:
truncate To eliminate without round-off some low-order bits, often after performing an arithmetic
Tschebyscheff See Chebyshev (11 of 12) [10/3/04 12:31:05 AM]
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TTL (transistor transistor logic) The workhorse digital logic integrated circuit family introduced as a
standard product line in 1964.
TTM (turntablist transcription methodology) A system of music notation developed by John Carluccio
in 1997, for turntablism (see below). His system uses a modified musical staff with the vertical axis
representing the direction of rotation of the record and the horizontal axis representing time. A free
descriptive pamphlet is available at Battle Sounds -- look for Free Download: The Turntablist
Transcription Methodology.
tube See: vacuum tube.
turntablism A form of music founded by turntablists (see below), that is already mainstream enough
that the Berklee College of Music publishing arm, Berklee Press has issued books and vinyl records for
this music form. For further historical info see Miles White's "The Phonograph Turntable and
Performance Practice in Hip Hop Music".
turntablist A performing artist who uses two or more turntables as music sources from which he/she
creates original results by quickly cutting and mixing the sounds of each, using specially designed
performance mixers such as Rane's TTM 54i.
turntablist transcription methodology See TTM
tweeter High-frequency loudspeaker. See crossover; also ribbon tweeter
twin-tone IMD See: IM
TwinVQ (transform-domain weighted interleave vector quantization) Name of a music compression
technology developed at the NTT Human Interface Laboratories in Japan. A transform coding method
like MP3, AAC or AC-3.
twisted-pair Standard two-conductor copper cable, with insulation extruded over each conductor and
twisted together. Usually operated as a balanced line connection. May be shielded or not. See cables.
two-bit Costing or worth 25 cents: a two-bit cigar.
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"U" Abbreviation for the "modular unit" on which rack panel heights are based. Per the EIA and ANSI
standard ANSI/EIA-310-D-1992 Cabinets, Racks, Panels, and Associated Equipment, the modular unit is
equal to 44.45 millimeters (1.75"). Panel heights are referred to as "nU" where n is equal to the number
of modular units. Examples are 1U (1.75" high), 2U (3.5" high), 3U (5.25" high), etc. Popularly called
rack units and often abbreviated "RU," which is technically incorrect but not misleading.
UART (universal asynchronous receiver-transmitter) The device that performs the bidirectional
parallel-to-serial data conversions necessary for the serial transmission of data into and out of a
uber or über A German term that literally means 'over,' but which is used in academia to refer to the
fundamental essence of a concept or idea. Popularly used to mean 'very' or 'really,' as in "Rane audio is
uber audio." Hit the link to read 100 different definitions.
UDP (user datagram protocol) A TCP/IP protocol describing how messages reach application programs
within a destination computer. This protocol is normally bundled with IP-layer software (UDP/IP). UDP
is a transport layer, connectionless mode protocol, providing a datagram mode of communication for
delivery of packets to a remote or local user. UDP/IP has almost no error recovery services, and is used
primarily for broadcasting messages over a network.
UDP/IP (user datagram protocol/internet protocol) See: UDP above.
UI (user interface) As compared with GUI.
ULD (ultra low delay coder) One of Fraunhofer's (creator of MP3) proprietary forms of digital audio
ULSI (ultra-large-scale integration) A logic device containing a million or more gates.
ultrasonic Of or relating to acoustic frequencies above the range audible to the human ear, or above
approximately 20,000 hertz. (AHD) Compare with supersonic.
ultrasonography 1. Diagnostic imaging in which ultrasound is used to image an internal body structure (1 of 4) [10/3/04 12:31:10 AM]
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or a developing fetus. Also called echography. 2. An imaging technique that uses high frequency sound
waves to visualize underwater surfaces, boundaries, objects, and currents. (AHD)
umpo "In music, taking a song or a part of a song up tempo, or faster." Compare
with: dempo.
unbalanced line See: balanced line
uncertainty principle See: Heisenberg uncertainly principle.
underground (music) Any avant-garde, experimental, or subversive movement in popular art, films,
music, etc. (Collins)
Unicode A universal system that provides a unique number for every character, regardless of platform,
program, or language.
unidirectional microphone or just directional microphone One that is most sensitive to sound arriving
directly at its front. Compare: omnidirectional mic and cardiod microphone
uniform array See: line arrays
uniform coverage horn See: constant directivity (CD) horn.
units of measurement See Rowlett's How Many? A Dictionary of Units of Measurement for a valuable
list (with definitions) of the International System of Weights and Measures, the metric system, and all
English customary units. Very highly recommended.
unity gain A gain setting of one, or a device having a gain of one, i.e., it does not amplify or attenuate
the audio signal. The output equals the input. See RaneNote: Unity Gain and Impedance Matching:
Strange Bedfellows.
unity power factor In an AC circuit, a power factor equal to one, which only occurs when the voltage
and current are in phase, i.e., for a purely resistive circuit, or a reactive circuit at resonance.
unobtainium Reference to all those parts necessary to keep legacy audio devices running that you can
never find -- things like old ICs, connectors, etc. [Origin unknown, but thanks to CD for passing it on.]
Upping some real crazy riffs. Playing cool music. (Decharne)
uproar Disorderly tumult together with loud, bewildering sound; a heated controversy. [AHD] (2 of 4) [10/3/04 12:31:10 AM]
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UPS (uninterruptible power supply) A back-up power supply (commonly used with computers) that
automatically continues to supply power when the main AC source fails.
upstage Theater. The back of the stage farthest from the audience, as opposed to downstage.
upward expander See expander.
Urban Dictionary A slang dictionary of user made up definitions, as if the English language isn't
difficult enough already. Makes 'um up as yus needs 'em.
URL (uniform resource locator) A Web address. A consistent method for specifying Internet resources
in a way that all Web browsers understand. For example, "," is the URL for Rane's
home page on the web. The "http" part tells the Web browser what protocol to use, and the remainder of
the URL, "," is the Internet address.
USB (universal serial bus) A low-speed (12 Mbits/sec) serial bus that acts like a special purpose local
area network. Originally proposed by a consortium of Compaq, Digital, IBM, Intel, Microsoft, NEC and
Northern Telecom in March of 1995, it is now the standard PC serial connection. USB equipped
machines typically have only three ports: USB, monitor, and Ethernet LAN . The USB port supports 63
devices, and eliminates the need for all specialized parallel, serial, graphics, modem, sound/game or
mouse ports. USB is completely "plug and play," i.e., it detects and configures all devices automatically,
and allows "hot swapping" of devices. See: IEEE-1394 for complementary high-speed system.
USITT (United States Institute for Theatre Technology) The association of design, production, and
technology professionals in the performing arts and entertainment industry.
USPTO (U.S. Patent & Trademark Office) Complete patent and trademark information is available free
at this incredible website. To search, read and print any U.S. patent granted since 1790 (really) click
here. [To download exact full-page patent images, complete with diagrams, requires you have a TIFF
plug-in. All Internet US patents are in TIFF image file format, using CCITT Group 4 compression, as
mandated by international standards. This requires third-party software to view these images either
directly or after conversion to another format, such as Adobe PDF. A free, unlimited time TIFF plug-in
offering full-size, unimpeded patent viewing and printing unimpeded by any advertising on Windows x86
PCs is available from AlternaTIFF].
UTP (unshielded twisted-pair) See cables.
UV (ultraviolet) Electromagnetic radiation at frequencies higher than visible light yet lower than those of
x-rays. Commonly used to erase EPROMs and in wireless and fiber optic data transmission. (3 of 4) [10/3/04 12:31:10 AM]
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uxoriousness 1. Excessively submissive or devoted to one's wife. 2. "A perverted affection that has
strayed to one's own wife." -- Ambrose Bierce.
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VA (voltampere) See voltampere.
vacuum-tube op amps Bob Pease posts the best information on vacuum-tube operational amplifiers.
vaporware Refers to either hardware or software that exist only in the minds of the marketeers.
vacuum tube An electron tube where virtually all the air has been removed (creating a vacuum), thus
permitting electrons to move freely, with low interaction with any remaining air molecules. (AHD) The
first tube was a two-element diode, invented and patented by Ambrose Fleming in 1904, based on the
Edison effect. Three years later, in 1907, Lee de Forest developed the first triode (known as the Audion)
by adding a grid between the cathode (emitter) and the anode (collector), thus creating the first amplifier
since a change of voltage at the grid produced a corresponding (but greater) change of voltage at the
valance Theater. A part of the stage draperies, usually ornamental, which hangs in front of the main
valence Chemistry. The combining capacity of an atom or radical determined by the number of electrons
that it will lose, add, or share when it reacts with other atoms. [AHD]
values, standard component values Resistors and capacitors. See: Standard Component Values
valve British term for vacuum tube, popularized because the first tube was known as the Fleming valve
named for its inventor Ambrose Fleming.
variable-Q graphic equalizer See: proportional-Q graphic equalizer.
VCA (voltage-controlled amplifier) An electronic circuit comprised of three terminals: input, output and
control. The output voltage is a function of the input voltage and the control port. The gain of the stage is
determined by the control signal, which is usually a DC voltage, but could be a current signal or even a
digital code. Usually found as the main element in dynamic controllers, such as compressors, expanders,
limiters, and gates. See THAT Corporation's VCA History. (1 of 6) [10/3/04 12:31:14 AM]
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VCXO (voltage-controlled crystal oscillator) A crystal-based oscillator whose frequency is controllable
by an external voltage.
V-DOSCA trademark of L-Acoustics, the "V" refers to the V-shaped acoustic lens configuration
employed for their mid and high frequency line array sections. The "DOSC" is a French acronym for
"Diffuser d'Onde Sonore Cylindrique"-- in English this translates to "cylindrical wave generator," an apt
description of the performance of their line arrays.
VDT (video display terminal) Computer monitor, or data terminal with a monitor.
vector Mathematics. A quantity, such as velocity, completely specified by a magnitude and a direction.
vector diagram A drawing that shows the direction and magnitude of a quantity by a vector arrow. See
RaneNote: Linkwitz-Riley Crossovers up to 8th-Order: An Overview.
vegetable diode See LEVD
vegetable orchestra See: Viennese Vegetable Orchestra
velocimeter Acoustics. A device for measuring the speed of sound in a liquid, usually water. Typically
done using two transducers arranged as a transmitting and receiving pair, located a fixed distance apart.
A short acoustic pulse is transmitted between the two and the travel time measured.
velocitySynthesizers & MIDI. How fast a key is depressed. Used to control loudness or other
velocity microphone See ribbon microphone
velocity of sound Acoustics. The international standard is 331.45 m/s (1087.42 ft/s) at 0 °C (32 °F) and
0% humidity. For the effects of temperature and humidity see: Bohn, Dennis A. "Environmental Effects
on the Speed of Sound," J. Audio Eng. Soc., Vol. 36, No. 4, April 1988, pp. 223-231.
Venn diagrams Mathematics. A logic diagramming system invented by the British logician, John Venn
(1834-1923) that uses overlaping circles to represent mathematical sets and their relationships.
vented loudspeaker See: bass reflex.
vertical interval time code See: time code.
VHS (video home system) Trademark for the most popular video tape format, invented by JVC in 1976. (2 of 6) [10/3/04 12:31:14 AM]
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vibrato A tremulous or pulsating effect produced in an instrumental or vocal tone by minute and rapid
variations in pitch. [AHD]
Victor Shorten form for The Victor Talking Machine Company (1901-1929). The company was named
"The Victor" in honor of legal victories by founder Eldrige R. Johnson and Emile Berliner over
Zonophone and others concerning their rights to patents on and distribution of their products.
Victrola The copyrighted name given to the line of internal horn phonographs made by the Victor
Talking Machine Company.
videoconferencing Video and audio communication held by two or more people over a distance using a
codec at either end and linked by digital networks (T-1, ISDN, etc.). Contrast with teleconferencing.
Viennese Vegetable Orchestra Music. Innovative (to say the least!) Austrian ensemble that plays nine
different instruments carved and peeled from ordinary garden vegetables, played by three men and six
vinyl Common name for any phonograph record.
violet noise See noise color
virginal Musical Instrument. A small, legless rectangular harpsichord popular in the 16th and 17th
centuries. Believed so called, because commonly used by young ladies. [AHD]
virus A self-replicating program released into a computer system for mischievous reasons. Once
triggered by some preprogrammed event (often time or date related), the results vary from humorous or
annoying messages, to the destruction of data or whole operating systems. Bad bad.
VITC (vertical interval time code) See: time code.
VJ (video jockey) 1. Term coined by the MTV generation for jocks that present music videos on
television or nightclubs or parties. [Or for us old farts: V-J Day, the date of Allied victory over Japan,
World War II, August 15, 1945.]
VLSI (very-large-scale integration) Refers to the number of logic gates in an integrated circuit. By
today's standards, a VLSI device could contain up to one million gates.
vocoder (voice coder) 1. Invented by Homer Dudley (no fooling) in 1936 at Bell Labs, and called a
"phase vocoder." It was an electronic device for analyzing and synthesizing, or generating artificial (3 of 6) [10/3/04 12:31:14 AM]
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speech. Homer Dudley was the first person to recognized that the basic information rate of speech is low
and that if you broke it down into its basic components, these could be transmitted over a quite narrow
bandwidth, and then reconstructed at the receiving end. Thus was born the speech synthesizer. The
vocoder principal is based on determining the formants, or vowel sounds, of the speech signal, along
with its fundamental frequency and any noise components such as plosive sounds (a speech sound
produced by complete closure of the oral passage and subsequent release accompanied by a burst of air,
as in the sound (p) in pit, or (d) in dog), hisses, or buzzes. Typically this is done by using two sets of
filter banks -- one for analysis and one for synthesis -- and an "excitation analysis" block. The analysis
filter bank is much like those used in real-time analyzers. The audio is presented to a bank of parallel
connected bandpass filters, whose output levels are converted into DC voltage levels proportional to the
signal passing through each bandpass filter. This captures the formant information. The excitation
analysis block determines and codes the fundamental frequency and noise attributes. Reconstruction
occurs by using the encoded DC levels, mixed with the excitation block output, to gate each output
bandpass filter, which are then summed together to recreate a facsimile of the original speech signal.
Early pictures and audio samples (from Prof. Edward A. Lee, UC Berkeley). 2. Once vocoder basics
were established, they found new uses in electronic music applications. The MI (musical instrument)
vocoder uses speech input to modulate another music instrument signal so that it "talks." Use of vocoders
peaked in the '70s after being popularized by such notables as Wendy Carlos, Alan Parsons and Stevie
Wonder. This vocoder version has two inputs, one for the vocal microphone and one for another
instrument. Talking or singing into the microphone modulates or superimposes vocal characteristics onto
the other instrument. Compare with talk box
VoFi (voice-over-IP-over-Wi-Fi) The technology that allows normal telephone calls to be made over the
voice Music. a. Musical sound produced by vibration of the human vocal cords and resonated within the
throat and head cavities. b. The quality or condition of a person's singing: a baritone in excellent voice. c.
A singer: a choir of excellent voices. d. One of the individual vocal or instrumental parts or strands in a
composition: a fugue for four voices; string voices carrying the melody. Also called voice part. [AHD]
Synthesizers. Playing two or more pitches at the same time.
voice box Popular term for the human larynx: "The part of the respiratory tract between the pharynx and
the trachea, having walls of cartilage and muscle and containing the vocal cords enveloped in folds of
mucous membrane." [AHD].
voice coil See loudspeaker
voiceover 1. The voice of an unseen narrator, or of an onscreen character not seen speaking, in a movie
or a television broadcast. 2. A film or videotape recording narrated by a voiceover. [AHD] Common
examples of voiceovers include cartoon characters, documentary videos of all types, computer software
tutorials, audio books, and automated telephone messages. (4 of 6) [10/3/04 12:31:14 AM]
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VoIP (voice over Internet protocol) The technology that allows you to transmit voice conversations (i.e.,
the ability to make telephone calls) and send faxes over a data network using the Internet Protocol.
Think, voice email.
volatile Refers to a memory device that loses any data it contains when power is removed from the
device. Examples would include static and dynamic RAMs.
volt Abbr. E, also V. The International System unit of electric potential and electromotive force, equal to
the difference of electric potential between two points on a conducting wire carrying a constant current of
one ampere when the power dissipated between the points is one watt. [After Count Alessandro Volta.]
Volta, Count Alessandro (1745-1827) Italian physicist who invented the battery (1800). The volt is
named in his honor. (AHD)
voltage follower See buffer amplifier
voltampere (VA) The product of rms voltage and rms current in an electronic circuit. It is the unit of
apparent power in the International System of Units (SI).
VOM (volt-ohm-milliammeter) A portable test instrument for measuring voltage (volts), resistance
(ohms) and current (amperes). Also see VTVM
voodoo boilers A kit of drums. (Decharne)
vote "The instrument and symbol of a freeman's power to make a fool of himself and a wreck of his
country." -- Ambrose Bierce.
VOX (voice operated exchange) Also called voice operated relay, originally a tape recorder feature
where speech starts the recording process and silence stops it. However it is not restricted to tape
recorders, for instance, cellular phones use VOX to save battery life, and teleconferencing systems use it
to determine the number of active mics. See NOM.
VRML (virtual reality modeling language) A method for describing interactive 3D scenes delivered
across the internet. In short, VRML adds 3D data to the Web. At on time heavily supported by Silicon
Graphics (SGI) workstations, competing with Sun's Java loaded workstations.
VSWR (voltage standing-wave ratio) Electronics. A waveguide mode: it is the ratio of the magnitude of
the transverse electric field in a plane of maximum strength to the magnitude at the equivalent point in an
adjacent plane of minimum filed strength. (IEEE) For pro audio it shows up in qualifying coax cables, (5 of 6) [10/3/04 12:31:14 AM]
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where it is a measure of return loss. It is a measure of the reflected energy from a transmitted signal, and
is affected by such factors as poor connectors, connections, cable defects and abuse.
VTVM (vacuum tube voltmeter) Antiquated term for a test instrument measuring voltage, resistance and
current, constructed using vacuum tubes, which required plugging it into an AC voltage source, thus not
portable. Characterized by having very high input impedance (compared to the standard VOM) that
allowed more precise measurements. Replaced today by solid-state DMM (digital multimeter).
vulcanized fiber See: fishpaper
vulgar fractions Chiefly British term for common fractions, although sometimes used to mean improper
fractions (those with a larger numerator than denominator). [Word History: Vulgar is an example of
pejoration, the process by which a word develops negative meanings over time. The ancestor of vulgar,
the Latin word vulgris (from vulgus, "the common people"), meant "of or belonging to the common
people, everyday," as well as "belonging to or associated with the lower orders." Vulgris also meant
"ordinary," "common (of vocabulary, for example)," and "shared by all."] (AHD)
VU meter (volume unit) The term volume unit was adopted to refer to a special meter whose response
closely related to the perceived loudness of the audio signal. It is a voltmeter with standardized dB
calibration for measuring audio signal levels, and with attack and overshoot (needle ballistics) optimized
for broadcast and sound recording. Jointly developed by Bell Labs, CBS and NBC, and put into use in
May, 1939, VU meter characteristics are defined by ANSI specification "Volume Measurements of
Electrical Speech and Program waves, " C16.5-1942 (which is know incorporated into IEC 60268-17). 0
VU is defined to be a level of +4 dBu for an applied sine wave. The VU meter has relatively slow
response. It is driven from a full-wave averaging circuit defined to reach 99% full-scale deflection in 300
ms and overshoot not less than 1% and not more than 1.5%. Since a VU meter is optimized for perceived
loudness it is not a good indicator of peak performance. Contrast with PPM.
VXCO (voltage-controlled crystal oscillator A crystal-based oscillator whose center frequency can be
varied with an applied voltage.
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W3 An abbreviation for World Wide Web.
Walker, Peter J. (1916–2003) British engineer and inventor best known as the founder of the legendary
British audio company Quad.
walla The film industry term for background crowd noises in a movie.
Walla Walla A city in southeast Washington near the Oregon border south-southwest of Spokane.
Founded in 1856 near the site of an army fort, it is a manufacturing center in an agricultural region
famous for sweet yellow onions. In spite of its name, a quiet community.
WAN (wide area network) A computer and voice network bigger than a city or metropolitan area.
warp marker Music Software. A method that attaches a position in a music sample to a particular time
in the song. It forces the software to arrive at a specific point in the music sample at a specific time.
watermarking 1. Paper The act of adding a translucent design impressed on paper during manufacture
and visible when the paper is held to the light. (AHD) 2. Audio or video Embedded data code within the
digitized audio or video image that can be recovered but which will not affect the quality of the product.
Various methods exist, but all consist of very short (2-5 microseconds long) pieces of code containing all
the relevant data about the copyright owner and performance royalties. All make use of the science of
watt Abbr. W Electricity An International System unit of power equal to one joule per second. [After
James Watt.] (AHD)
Watt, James (1736-1819) British engineer and inventor who made fundamental improvements in the
steam engine, resulting in the modern, high-pressure steam engine (patented 1769). (AHD)
watts rms No such thing. See apparent power and rms power.
.WAV File extension for a Wave file, the Microsoft format that is the de facto audio file format for PCs. (1 of 7) [10/3/04 12:31:18 AM]
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wavefield synthesis "A means by which a soundfield can be reconstructed within a listening area using
an array of loudspeakers, enabling faithful spatial reproduction." From "Wavefield Synthesis," J. Audio
Eng. Soc., Vol. 52, No. 5, May 2004, pp. 538-543.
wavelength Symbol (Greek lower-case lambda, &#955) The distance between one peak or crest of a sine
wave and the next corresponding peak or crest. The wavelength of any frequency may be found by
dividing the speed of sound by the frequency.
wavelet Mathematics. An algorithm used to efficiently compress and decompress the phase and
frequency information contained in a transmitted signal.
wax a disc To make a recording. (Decharne)
Webcast The real time (continuous stream) delivery of audio and video from a server to a client. [Think
weber Abbr. Wb The International System unit of magnetic flux, equal to the flux that produces in a
circuit of one turn an electromotive force of one volt, when the flux is uniformly reduced to zero within
one second. After Wilhelm Eduard Weber (1804-1891), German physicist. (AHD)
Web ring A group of websites all sharing a common theme. For example, web rings exist for fans of
certain bands, movies, TV shows, authors, racecar drivers, etc. Soon we will have a web ring for web
weighting filters Special filters used in measuring loudness levels, and consequently carried over into
audio noise measurements of equipment. The filter design "weights" or gives more attention to certain
frequency bands than others. The goal is to obtain measurements that correlate well with the subjective
perception of noise. [Technically termed psophometric (pronounced "so-fo-metric") filters, after the
psophometer, a device used to measure noise in telephone circuits, broadcast, and other audio
communication equipment. A psophometer was a voltmeter with a set of weighting filters.] Weighting
filters are a special type of band-limiting filters designed to compliment the way we hear. Since the ear's
loudness vs. frequency response is not flat, it is argued, we should not try to correlate flat frequency vs.
loudness measurements with what we hear. Fair enough. Five weighting filter designs dominate (See:
References: Metzler):
A-weighting (not official but commonly written as dBA) The A-curve is a wide bandpass
filter centered at 2.5 kHz, with ~20 dB attenuation at 100 Hz, and ~10 dB attenuation at 20
kHz, therefore it tends to heavily roll-off the low end, with a more modest effect on high
frequencies. It is the inverse of the 30-phon (or 30 dB-SPL) equal-loudness curve of
Fletcher-Munson. [Editorial Note: Low-cost audio equipment often list an A-weighted
noise spec -- not because it correlates well with our hearing -- but because it helps "hide" (2 of 7) [10/3/04 12:31:18 AM]
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nasty low-frequency hum components that make for bad noise specs. Sometimes Aweighting can "improve" a noise spec by 10 dB. Words to the wise: always wonder what a
manufacturer is hiding when they use A-weighting.]
C-weighting (not official but commonly written as dBC) The C-curve is "flat," but with
limited bandwidth, with -3 dB corners of 31.5 Hz and 8 kHz, respectively.
ITU-R 468-weighting (was CCIR, but since the CCIR became the ITU-R, the correct
terminology today is ITU-R) This filter was designed to maximize its response to the types
of impulsive noise often coupled into audio cables as they pass through telephone
switching facilities. Additionally it turned out to correlate particularly well with noise
perception, since modern research has shown that frequencies between 1 kHz and 9 kHz
are more "annoying" than indicated by A-weighting curve testing. The ITU-R 468-curve
peaks at 6.3 kHz, where it has 12 dB of gain (relative to 1 kHz). From here, it gently rolls
off low frequencies at a 6 dB/octave rate, but it quickly attenuates high frequencies at ~30
dB/octave (it is down -22.5 dB at 20 kHz, relative to +12 dB at 6.3 kHz).
ITU-R (CCIR) ARM-weighting or ITU-R (CCIR) 2 kHz-weighting This curves derives
from the ITU-R 468-curve above. Dolby Laboratories proposed using an average-response
meter with the ITU-R 468-curve instead of the costly true quasi-peak meters used by the
Europeans in specifying their equipment. They further proposed shifting the 0-dB
reference point from 1 kHz to 2 kHz (in essence, sliding the curve down 6 dB). This
became known as the ITU-R ARM (average response meter), as well as the ITU-R 2 kHzweighting curve. (See: R. Dolby, D. Robinson, and K. Gundry, "A Practical Noise
Measurement Method," J. Audio Eng. Soc., Vol. 27, No. 3, 1979) [Before using these
terms be aware that the ITU-R, even after 20 years, takes strong exception to having its
name used by a private company to promote its own methodologies.]
Z-weighting A new term defined in IEC 61672-1, the latest international standard for
sound pressure level measurements. It stand for zero-weighting, or no weighting; i.e., a flat
measurement with equal emphasis of all frequencies.
wet Recording. 1. The result of mixing the original recorded sound with the processed sound (reverb,
chorusing, doubling, etc.). 2. Any sound with significant reverberation; not dead. Contrast with dry.
wet circuit See below.
wet transformer Telephony. An analog audio transformer designed for both DC and AC operation.
Derived from the term, wet circuit, referring to a circuit where voice signals are transmitted and also
carries direct current. Contrast with dry transformer.
WFAE (World Forum for Acoustic Ecology) "An interdisciplinary spectrum of individuals engaged in
the study of the scientific, social, and cultural aspects of natural and human made sound environments."
WFS (wavefield synthesis) See: wavefield synthesis. (3 of 7) [10/3/04 12:31:18 AM]
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Wheatstone bridge 1. An instrument used for measuring resistance. The circuit used is a 4-arm bridge,
all arms of which are predominantly resistive. The bridge is a two-port network (i.e., it has two terminal
pairs across opposite corners) capable of being operated in such a manner that when voltage is applied to
one port, by suitable adjustment of the resistive elements in the network, zero output can be obtained at
the signal output port (usually a meter). Under these circumstances the bridges is termed balanced.
[Although the circuit used in a Wheatstone bridge was first described by Samuel Hunter Christie (17841865) -- the son of James Christie, founder of the well-known auction house -- in his paper
"Experimental Determination of the Laws of Magneto-electric Induction" (1833), Sir Charles
Wheatstone(1802-1875) received credit for its invention because of his adaptation of the circuit in 1843
for the measurement of resistance. Wheatstone also invented the concertina, the stereoscope and
contributed significantly to the development of the telegraph.]
whippin' that ivory Playing the piano. (Decharne)
white noise 1. Physics. Analogous to white light containing equal amounts of all visible frequencies,
white noise contains equal amounts of all audible frequencies (technically the bandwidth of noise is
infinite, but for audio purposes it is limited to just the audio frequencies). From an energy standpoint
white noise has constant power per hertz (also referred to as unit bandwidth), i.e., at every frequency
there is the same amount of power (while pink noise, for instance, has constant power per octave band of
frequency). A plot of white noise power vs. frequency is flat if the measuring device uses the same width
filter for all measurements. This is known as a fixed bandwidth filter. For instance, a fixed bandwidth of
5 Hz is common, i.e., the test equipment measures the amplitude at each frequency using a filter that is 5
Hz wide. It is 5 Hz wide when measuring 50 Hz or 2 kHz or 9.4 kHz, etc. A plot of white noise power vs.
frequency change is not flat if the measuring device uses a variable width filter. This is known as a fixed
percentage bandwidth filter. A common example of which is 1/3-octave wide, which equals a bandwidth
of 23%. This means that for every frequency measured the bandwidth of the measuring filter changes to
23% of that new center frequency. For example the measuring bandwidth at 100 Hz is 23 Hz wide, then
changes to 230 Hz wide when measuring 1 kHz, and so on. Therefore the plot of noise power vs.
frequency is not flat, but shows a 3 dB rise in amplitude per octave of frequency change. Due to this
rising frequency characteristic, white noise sounds very bright and lacking in low frequencies. [Here's the
technical details: noise power is actually its power density spectrum - a measure of how the noise power
contributed by individual frequency components is distributed over the frequency spectrum. It should be
measured in watts/Hz; however it isn't. The accepted practice in noise theory is to use amplitude-squared
as the unit of power (purists justify this by assuming a one-ohm resistor load). For electrical signals this
gives units of volts-squared/Hz, or more commonly expressed as volts/root-Hertz. Note that the
denominator gets bigger by the square root of the increase in frequency. Therefore, for an octave
increase (doubling) of frequency, the denominator increases by the square root of two, which equals
1.414, or 3 dB. In order for the energy to remain constant (as it must if it is to remain white noise) there
has to be an offsetting increase in amplitude (the numerator term) of 3 dB to exactly cancel the 3 dB
increase in the denominator term. Thus the upward 3 dB/octave sloping characteristic of white noise
amplitude when measured in constant percentage increments like 1/3-octave.] See noise color. 2. Music.
Slang term for music that is discordant with no melody; disagreeable, harsh or dissonant. (4 of 7) [10/3/04 12:31:18 AM]
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wide-range curve Same as X curve
widget (perhaps alteration of gadget) 1. A small mechanical device or control; a gadget. 2. An unnamed
or hypothetical manufactured article. (AHD) 3. As developed by Guinness, a small disk with a pinpricksize hole that fits inside their beer cans. As the beer is packaged, a small amount of stout is forced into
the widget and held there under pressure. Once the pressure is released by opening the can, the beer is
freed from the widget and a stream of bubbles flows upward. Now when the stout is poured, it looks like
a pub-poured draught with the characteristic Guinness head (thick collar of foam), without the widget it
looks like any other beer. It also reproduces the creamy texture and low carbonation of a draught pint.
Now also used by Murphy's and Beamish.
Wi-Fi (wireless fidelity) Shorten form for the Wi-Fi Alliance, a nonprofit international association
formed in 1999 to certify interoperability of wireless Local Area Network products based on IEEE
802.11 specification. Wi-Fi Certification results from testing 802.11-based wireless equipment to make
sure it meets the Wi-Fi standard and works with all other manufacturers' Wi-Fi equipment on the market.
wiki wiki Hawaiian word meaning “quick” used to create the name of Wikipedia, the free encyclopedia
– a fantastic resource.
Williwaw Name for howling ferocious cold winds common to Alaska and the Straits of Magellan.
windshield Microphones. Slang for a pop filter.
Wintel A contraction of the words "Windows" and "Intel." Used to describe personal computers made
from Intel microprocessors and running Microsoft Windows software. It is reported that this "Wintel
standard" accounts for 80% of all PCs.
WIPO (World Intellectual Property Organization) "An international organization dedicated to helping
to ensure that the rights of creators and owners of intellectual property are protected worldwide and that
inventors and authors are, thus, recognized and rewarded for their ingenuity."
wire See cables
wiring classes U.S. National Electrical Code (NEC) defines three classes of wiring according to their
fire and shock hazard potential:
Class 1 Where both fire and shock hazards exist, i.e., the wiring can deliver enough
current for a fire hazard and enough voltage for a shock hazard. The most common
example is AC power running to equipment. This class requires prevention of all
touching and barriers against fire. (5 of 7) [10/3/04 12:31:18 AM]
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Class 2 Where neither fire or shock hazard exists, i.e. the wiring cannot deliver
enough current (internal limiting) for a fire hazard and not enough voltage (less
than 120 Vrms) for a shock hazard. Examples here are all normal audio
interconnect plus most power amplifier output wiring.
Class 3 Where there is not a fire hazard but there is a shock hazard, i.e., the wiring
cannot deliver enough current (internal limiting) for a fire hazard, but can deliver
enough voltage (120 – 300 Vrms) for a shock hazard. Requires touch-proof
terminals; seen in audio for very high-output power amplifiers.
WOM (write-only-memory) Term coined by Signetics in 1972 for their 25000 Series 9046XN Random
Access Write-Only-Memory integrated circuits. Based on SEX (Signetics EXtra secret) processes, these
devices employ both enhancement and depletion mode P-Channel, N-Channel, and NEU-Channel MOS
transistors (devices which simultaneously, randomly, or not at all, enhance or deplete regardless of gate
polarity). The world's supply of WOMs was quickly consumed by newly designed airline baggagehandling equipment, where they are still used today to store the exact real-time location of each bag.
WOM production was suddenly discontinued when it was discovered that the only copy of the mask code
had been accidentally filed into a WOM location.
woodpile Hipster slang for a xylophone. (Decharne)
woofer Low-frequency loudspeaker. See crossover
word An ordered set of bits that is the normal unit in which information may be stored, transmitted, or
operated upon within a given computer - commonly 16 or 32 bits.
word clock The synchronizing signal that indicates the sampling frequency or rate of sample words over
a digital audio interface.
word length The number of bits in a word.
World Wide Web (WWW and/or W3) 1. A way to present resources and information over the Internet,
or according to its inventor, British scientist Tim Berners-Lee, while at CERN in 1989, "The World
Wide Web (W3) is the universe of network-accessible information, an embodiment of human
knowledge." 2. Satirically called the World Wide Wait.
WOROM (write-once read-only memory) Systems in which data may be written once, but not erased
and rewritten. Usually refers to CD-ROM technology that can be recorded once only.
wow A form of distortion due to very slow (~ 1 Hz) variations in rotational speed common to turntables
and analog tape recorders. Heard as a slow variation in the pitch when played back. Compare with flutter. (6 of 7) [10/3/04 12:31:18 AM]
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WPAN (wireless personal-area network) For instance, see Bluetooth and ZigBee.
write To record data on a medium.
WWW (World Wide Web) See: World Wide Web.
wye connector See Y-connector.
WYSIWYG (pronounced "whizzy-wig") (what you see is what you get) Popular word processing term.
Folklore says it was copied from a catchphrase from the old TV show Rowan and Martin's Laugh-In .
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X The electronic symbol for reactance - the imaginary part of impedance.
XC The electronic symbol for capacitive reactance.
XL The electronic symbol for inductive reactance.
x-axis The horizontal axis of a two-dimensional Cartesian coordinate system, or one of three axes in a
three-dimensional Cartesian coordinate system. (AHD)
XBT (expendable bathythermograph) Acoustics. Abbreviation found in underwater acoustics studies.
See: bathythermograph
X curve (extended curve) In the film sound industry an X curve is also known as the wide-range curve
and conforms to ISO Bulletin 2969, which specifies for pink noise, at the listening position in a dubbing
situation or two-thirds of the way back in a theater, to be flat to 2 kHz, rolling off 3-dB/oct after that. The
small-room X curve is designed to be used in rooms with less than 150 cubic meters, or 5,300 cubic feet.
This standard specifies flat response to 2 kHz, and then rolling off at a 1.5 dB/oct rate. Some people use a
modified small-room curve, starting the roll-off at 4 kHz, with a 3 dB/oct rate. Compare with Academy
Xenakis, Iannis Greek composer who used flicker noise to randomly generate compositions he called
stochastic music.
xerography The name created by the Haloid Company in 1946 (from the Greek xeros for dry and
graphein for writing) for the process invented by Chester F. Carlson on October 22, 1938, which he
named electrophotography. In 1960, Haloid-Xerox introduced the 914 copier, the first pushbutton, plainpaper, xerographic office machine. The company soon became known simply as Xerox.
xfmr Electronics. Abbreviation for transformer.
X Generation See Generation X. (1 of 3) [10/3/04 12:31:21 AM]
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Xilinx®(pronounced zi-links; after xi the 14th letter of the Greek alphabet) Leading manufacturer of fieldprogrammable logic devices.
xingxong (sing-song) "A term used to describe a song which is overplayed." --
XLR See connectors.
XMF (extensible music format) A MIDI Manufacturers Association approved new standard that
combines MIDI notes with DLS (downloadable sound) samples.
XOR Acronym for exclusive OR, a type of logic gate where a logic 1 output is based upon A or B inputs
being present - but not both.
xovr Abbreviation for crossover.
X/R ratio Electronics. The ratio of reactance to resistance. It indicative of the rate of decay of any dc
offset. A large X/R ratio corresponds to a large time constant and a slow rate of decay. (IEEE)
xstr Electronics. Abbreviation for transistor.
XSV Underwater Acoustics. Abbreviation for expendable sound velocimeter.
XT Official (FED-STD-1037C) abbreviation for crosstalk.
xylophone A percussion instrument consisting of a mounted row of wooden bars graduated in length to
sound a chromatic scale, played with two small mallets. Word History: Alphabet books for children
frequently feature the word xylophone because it is one of the few words beginning with x that a child (or
most adults, for that matter) would know. The majority of English words beginning with x, including
many obscure scientific terms, are of Greek origin, the x, pronounced (z), representing the Greek letter xi.
In the case of xylophone, xylo- is a form meaning "wood," derived from Greek xulon, "wood," and -phone
represents Greek phn, "voice, sound," the same element found in words such as telephone, microphone,
and megaphone. This famous x-word is first recorded in the April 7, 1866, edition of the Athenaeum: "A
prodigy... who does wonderful things with little drumsticks on a machine of wooden keys, called the
'xylophone.'" (AHD) See: woodpile.
X-Y microphone technique A stereo recording technique where two cardioid microphones are placed
facing each other, at an angle of 90 degrees, with the center of the source aimed at the center between
them. Sometimes this technique is incorporated internally in a single microphone using two capsules.
Also called the coincident-microphone technique Compare with ORTF (2 of 3) [10/3/04 12:31:21 AM]
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xyz - "Examine your zipper." Example: "When seeing someone in class or at work with their zipper
down, you can discreetly say, "XYZ"" --
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Copyright © Rane Corporation. All rights reserved. (3 of 3) [10/3/04 12:31:21 AM]
Rane Professional Audio Reference (Y)
Pro Audio Reference
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Y 1. The electronic symbol for admittance - the inverse of impedance. 2. Abbreviation for luminance
(black & white) video signal. 3. Chemical symbol for yttrium - my absolute favorite element, next to
Y2k (year two thousand)
yackety-yack Prolonged, sometimes senseless talk. [AHD] After yack: a snapping sound; engaged in
trivial or unduly persistent talk or conversation; chatter. (Shorter Oxford English Dictionary, 5th ed.)
yada-yada Trivial, tedious, or meaningless talk or writing; chatter. (Shorter Oxford English Dictionary,
5th ed.) [And you thought Seinfeld writers made this up!]
YAG (yttrium-aluminum-garnet) A type of solid-state laser. Compare with YIG.
Yagi antenna Shortened form of Yagi-Uda antenna, a linear end-fire array consisting of a driven
element, a reflector element, and one or more director elements -- your basic TV antenna. [named after
Hidetsugu Yagi (1886-1976), laboratory director of Shintaro Uda, professor at Tohoku University in
Sendai, Japan.]
yahoo A crude or brutish person; a boor. [And you thought it was a search engine.]
y'allternative "Music known most commonly as 'country rock' which is a hybrid of modern alternative
rock and country music." --
yapped Book jargon Refers to the edge of the cover of a book bound in paper or other soft material.
Yapped edges are not flush with the pages but extend beyond the edges of the book making them fragile.
yarr To growl or snarl like a dog. (Lynch)
y-axis The vertical axis of a two-dimensional Cartesian coordinate system, or one of three axes in a threedimensional Cartesian coordinate system. (AHD)
YB (yottabyte) The number of bytes represented by 2 raised to the 80th power, i.e., (1 of 3) [10/3/04 12:31:24 AM]
Rane Professional Audio Reference (Y)
1,208,925,819,614,629,174,706,176 bytes.
Y/C video See S-video.
Y-connector or Y-cord A three-wire circuit that is star connected. Also spelled wye-connector. It is okay
to use a Y-connector to split an audio signal from an output to drive two inputs; it is not okay to use a Yconnector to try and sum or mix two signals together to drive one input. For details, see RaneNote: Why
Not Wye?
Yellow Book Nickname for the Philips and Sony's ECMA-130 standard document that defines the format
for CD-ROM (compact disc-read only memory) discs; available only to licensees. Compare with Red
Book and Green Book
yield The number of devices that work as planned, specified as a percentage of the total number actually
fabricated. Normally used to quantify a run of integrated circuits.
YIG (yttrium-iron-garnet) A crystalline material used in microwave devices. Compare with YAG.
[Don't confuse your 'yag-yig' with your 'ying-yang.']
Y/N Software program "yes/no" response prompt. A "Y" or "N" keystroke is expected.
Ynysddu Welsh district and home to Penny & Giles.
yoctosecond Abbr. ys or ysec One septillionth (10-24) of a second.
yoke 1. Any magnetic core interconnection material. 2. The deflection windings of a CRT. 3. A series of
two or more magnetic recording heads fastened securely together for playing or recording on more than
one track simultaneously. [AHD]
yottahertz Abbr. YHz One septillion (1024) hertz.
YRB (Yellow Rat Bastard) Website, magazine, clothes, music, newsletter, for the ultra hip, from NYC,
of course. Contains adult content. Check it out -- take the test.
Yttrium See definition three for "Y" above.
YUV video The coding process used in CD-I in which the luminance signal (Y) is recorded at full
bandwidth on each line and chroma values (U and V) are recorded at half bandwidth on alternate lines.
yux To hiccough. (Lynch) (2 of 3) [10/3/04 12:31:24 AM]
Rane Professional Audio Reference (Y)
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Copyright © Rane Corporation. All rights reserved. (3 of 3) [10/3/04 12:31:24 AM]
Rane Professional Audio Reference (Z)
Pro Audio Reference
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Z The electronic symbol for impedance.
zaa zaa Japanese. An onomatopoetic word meaning hard rain, hail, the sound of a heavy downpour or
rushing water.
zap To eradicate all or part of a program or database, sometimes by lightning, sometimes intentionally.
Zaphod Beeblebrox Douglas Adams' Hitchhiker's Guide To The Galaxy, President of the Universe
character, famous for being able to scream a diminished fifth.
Zappa, Frank Vincent (1940-1993) American composer. My favorite Zappa quote: "Rock journalism is
people who can't write interviewing people who can't talk for people who can't read."
z-axis One of three axes in a three-dimensional Cartesian coordinate system. (AHD)
zeal "A certain nervous disorder afflicting the young and inexperienced." -- Ambrose Bierce.
Zen The Sanskrit word for meditation.
zener or zener diode Electronics. A two terminal semiconductor device commonly use in power supply
reference circuits. It exhibits a stable voltage over a wide range of currents passing through it, creating a
constant-voltage characteristic.
zenith Analog Tape Recorders. Pertaining to the angular alignment of a tape head along its vertical axis
and at right angles to its azimuth; a forward/backward tilt of the head, when viewed from the front.
zentropic "The state of someone who has a shallow understanding of Zen, and uses it to excuse the fact
that she does absolutely nothing, on the basis that she is in tune with the Tao." -- (1 of 5) [10/3/04 12:31:28 AM]
Rane Professional Audio Reference (Z)
zeptosecond Abbr. zs or zsec One sextillionth (10-21) of a second.
zero Half of all the stored knowledge in computers. Compare with one; See Kaplan's The Nothing That
Is for its fascinating story.
zero crossing point Electronics. The point at which a signal waveform crosses from being positive to
negative or vice versa. This is the instant the signal has zero value, which makes it the spot where you
want to make changes with the least amount of zipper (or other) noise, e.g., change gain in VCAs, or
activate switches, transfer data, etc.
zero level or zero reference The reference point used for setting audio signal levels throughout a sound
system; usually +4 dBu for pro audio use; named for the original practice of using 0 dBm (then 0 dBu) as
the reference level.
zero lobing error Electronic crossovers. See lobing error.
zeros Mathematics. The roots of the numerator of a circuit transfer function, i.e., the values that make the
numerator equal zero. Compare with poles.
zettahertz Abbr. ZHz One sextillion (1021) hertz.
ZIF (zero insertion force socket) A standard IC-socket design requiring the user to move a lever to insert
or remove the chip -- as opposed to pressing and prying the chip manually -- hence, zero insertion force.
The lever actuator (hopefully) eliminates damaging the IC pins.
ZigBeeTM (formerly known as PURLnet, RF-Lite, Firefly, and HomeRF Lite.) A low-cost, lowpower, two-way, wireless communications standard between compliant devices anywhere in and around
the home (automation, toys, PC peripherals, etc.), developed by Philips and others. Claiming lower cost,
lower power consumption, higher density of nodes per network and simplicity of protocols, it is an
alternative to Bluetooth. [Not to be confused with the Zig Zag man.]
zilch 1. Zero; nothing. 2. A person regarded as being insignificant; a nonentity. 3. Amounting to nothing;
nil. [Perhaps from alteration of z(ero) + (n)il.] (AHD)
ZIP (zone improvement plan) As in "Zip Code.
Zippo. George G. Blaisdell invented the Zippo Windproof Lighter in 1932. The lighter was given its
name as a derivation of the word "zipper" because the inventor liked the sound of the word, which had
been patented in nearby Meadville, PA, in 1925 by B.F. Goodrich. (2 of 5) [10/3/04 12:31:28 AM]
Rane Professional Audio Reference (Z)
zipper noise Audible steps that occur when a parameter is being varied in a digital audio processor,
analog VCA, digitally-controlled attenuator, etc.
zither A musical instrument composed of a flat sound box with about 30 to 40 strings stretched over it
and played horizontally with the fingertips, a plectrum, or a bow, or set into vibration by the wind, as in
the Aeolian harp. (AHD)
Zobel network or Zobel filter [Also called Boucherot cell after Paul Boucherot who worked extensively
with electrical networks and power.] 1. A filter designed according to image parameter techniques. 2.
Audio amplifiers. Zobel networks are used in audio amplifiers to dampen out high frequency oscillations
that might occur in the absence of loads at high frequencies. It is the commonly seen series resistorcapacitor combination located directly at the output of the driver stage, just before the output inductor (in
analog power amplifiers). Typical values are 5-10 ohms in series with 0.1 microfarads. The network
limits the rising impedance of a loudspeaker due to the speaker coil inductance. The output inductor
found in most analog power amplifiers used to disconnect the load at high frequencies further aggravates
this phenomenon. See Douglas Self's book for a good discussion of audio amplifier Zobel networks. 3.
Loudspeakers. Some loudspeaker crossover designs include Zobel networks wired across the tweeter
(high frequency) driver to compensate for the rise in impedance at high frequencies due to the inductance
of the voice coil. The goal here is to try to keep the load seen by the crossover circuitry as resistive as
possible. [After Dr. Zobel's paper appearing in the Bell Labs Journal: Zobel, O. J., "Theory and Design
of Uniform and Composite Electric Wave Filters," Bell Sys. Tech. J., Vol. 2, pp. 1-46, Jan 1923.]
Zoetrope (pronounced ZOH-uh-trohp) A kind of mechanical cinema invented in 1834 by William
George Horner. It was an early form of motion picture projector consisting of a drum containing a set of
still images turned in a circular fashion to create the illusion of motion. Horner originally called it the
Daedatelum, but Pierre Desvignes, a French inventor, renamed his version of it the Zoetrope (from Greek
word root zoo for animal life and trope for "things that turn.") Like other motion simulation devices, the
Zoetrope depends on the fact that the human retina retains an image for about 100 milliseconds so that if
a new image appears in that time, the sequence was seem to be uninterrupted and continuous. It also
depends on what is referred to as the Phi phenomenon, which observes that humans try to make sense out
of any sequence of impressions, continuously relating them to each other.
zone Acoustics. Separate and distinct listening locations within a complex sound system acoustically
isolated from each other. A complex sound system is often broken up into zones with individual sound
treatment for each.
ZonophoneRecord Label. The name applied to the phonograph records and machines sold by founder
Frank Seaman from 1899-1903.
zoom microphone Microphone analogy to the zoom lens. A design that allows synchronization with a
zoom lens so that not only does the action get closer but the audio gets louder and focused. The trick is to (3 of 5) [10/3/04 12:31:28 AM]
Rane Professional Audio Reference (Z)
make the microphone pickup pattern, or directivity, and sensitivity change from omnidirectional (wideangle and wide soundstage) to super-cardiod. At full zoom this makes the microphone very directional
and is combined with higher preamp gain. This allows the audio and video to track is a realist fashion..
ZT Symbol for surface transfer impedance, the standard measurement used for quality rating of the RF
shielding performance of cables, connectors and shield terminations. It measures how much voltage
appears on the inner wires when the shield is driven by a strong RF signal and defines ZT as the induced
voltage divided by the shield test current.
z-transform A mathematical method used to relate coefficients of a digital filter to its frequency
response, and to evaluate stability of the filter. It is equivalent to the Laplace transform of sampled data
and is the building block of digital filters.
Z-weighting See weighting filters
Zwicker phons or Zwicker method or Zwicker loudness Acoustics. A single-number scale for rating
the loudness of complex sounds. It is based on a model that simulates the nonlinear operationof the
humanear, in contrast to simple frequency-weighting such as A-weighting. [Morfey] After Professor
Eberhard Zwicker (1924-1990).
Zwicker tone Acoustics. A psychoacoustic phenomena where subjects hear a "ghost" as an after tone
when presented with a broadband noise source having a "gap," that is, a small band (say, a 1/3-octave
band) missing. After the source stops, the subjects report hearing an afterimage centered in the missing
gap. [This is a case of hearing something that is not there, after hearing a source that did not contain
what you are hearing in the first place! Muy strange.]
zydeco Music. Popular music of southern Louisiana that combines French dance melodies, elements of
Caribbean music, and the blues, played by small groups featuring the guitar, the accordion, and a
washboard. (AHD)
zylon A thermoplastic polyurethane trade secret (a new high-performance fiber) developed by Toyobo of
Japan. The latest thing in tennis racquets and body armor with excellent ballistic impact properties .
[Someday someone will apply this to loudspeaker design -- remember, you read it here first.]
zymurgist See brewer
zymurgy The scientific study of the process of fermentation in brewing and distilling.
Zyzyyzyski, Zyzeikkel The last name listed in the 1998 Snohomish County, Washington, U.S.A.
telephone directory - really (but, alas, no more). (4 of 5) [10/3/04 12:31:28 AM]
Rane Professional Audio Reference (Z)
zyzzyva (The last word in the English dictionary) Any of various tropical American weevils of the genus
Zyzzyva, often destructive to plants. [New Latin Zyzzyva genus name probably from Zyzza former genus
of leafhoppers] (AHD)
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"… gotta keep the devil down in the hold …" (Tom Waits Way Down in the Hold) (5 of 5) [10/3/04 12:31:28 AM]
Your Session has Timed Out. Please go to the homepage and start over again. [10/3/04 12:32:16 AM]
Standing Wave and Room Mode Animations
Standing Wave and Room Mode
The following animated GIF files will be used to illustrate the concept of standing waves or modes.
Standing Waves
When plane waves of equal amplitude are travelling in opposite directions, they add in such a way as to
produce a wave that oscillates in amplitude but does not move in space. Such a wave field is called a
standing wave or a mode.
Standing waves are produced in ducts and rooms when there are strong reflections at walls or
terminations. In long ducts the waves traveling back and forth are usually plane waves. At frequencies
such that the wavelength is a multiple of 1/2 the duct length (L/2) the plane waves traveling in each
direction interfere properly to create a standing wave. The shape of the standing wave, or mode shape,
looks like cos( n π x/L) where n is an integer.
These special frequencies are called the resonance frequencies and are given by the equation fn=n c/(2 L)
where c is the speed of sound and L is the duct length. At these frequencies energy builds up in the room
and a very large sound field can result.
The locations where cos( n π x/L)=0 are called nodes. The places where cos( n π x/L) are ±1 are called
anti-nodes. At nodes the acoustic pressure is always zero.
If a source that has energy at the resonance frequency is located at a node, it cannot excite the mode and
sound will not build up. If a source is located at an anti-node, it can fully excite a mode and maximum
sound levels will result
The following animation shows two plane waves travelling in different directions and the summation of
the two waves which is a standing wave. The mode number, n, corresponds to the number of nodes in the
standing wave. In this animation there are 6 nodes so the mode number n=6. (1 of 4) [10/3/04 12:37:38 AM]
Standing Wave and Room Mode Animations
2-D and 3-D modes
In rooms, standing waves can be set up between all three sets of walls. The mode shape ends up being of
the form cos( nx π x/Lx)cos( ny π y/Ly)cos( nz π z/Lz) where nx, ny, and nz are all integers.
The resonance frequencies are given by the equation
f(nx,ny,nz) = c/2*sqrt( (nx/Lx)^2 + (ny/Ly)^2 + (nz/Lz)^2 )
In the animation below is shown a mode with nx=3, ny=2, nz=0. The top part of the animation shows the
the particle displacement and the bottom shows the pressure amplitude as a color with red being a high
acoustic amplitude and blue being a low acoustic amplitude. (2 of 4) [10/3/04 12:37:38 AM]
Standing Wave and Room Mode Animations
Important Note: Non parallel walls.
It is important to note that *all* room shapes have modes. It is a common fallacy that modes can be
eliminated by ensuring that walls are not parallel. It is also not true that modes are weaker if walls are not
parallel. Any room of any shape will have modes. If the room is not rectangular, you cannot easily
predict the resonance frequencies and location of nodes, but resonances still occur and nodes and antinodes still exist. The strength of a mode is determined only by room damping, the location of a source,
and the strength of the source - not by the shape of a room. One exception is if two or more modes have
approximately the same resonance frequency - then you get excitation of multiple modes which can
combine to give high sound levels.
There are fourteen seperable geometries in which the resonance frequencies and nodal locations can be
computed analytically. Any other shape (such as a triangle) the resonance frequencies and mode shapes
have to be computed numerically.
Credits (3 of 4) [10/3/04 12:37:38 AM]
Standing Wave and Room Mode Animations
These GIFs were generated from AVI movies created in MATLAB V6.0 using the Ulead Gif Animator.
The idea came from GIF animations developed by Prof. Daniel Russel and Quicktime movies developed
by Prof. Vic Sparrow, both of whom were inspired by the Mathematica Notebook SoundWaves.nb
developed by Mats Bengtsson.
If you are interested in obtaining the source code to these animations, please contact Ralph Muehleisen
by email at [email protected] (4 of 4) [10/3/04 12:37:38 AM]
Auralex Acoustics - Auralex Book Referrals Page.
Books On Acoustics - Auralex Referral Page.
Site Search
Featured Products
Master Handbook of Acoustics
Hands down, the most "bang for your buck" book on this list.
It covers all the facets of acoustics in easy to understand
terms. Some technical and mathematical concepts are
discussed in detail, but all in all this a great reference for
people looking to better understand room acoustics.
Read more about this book...
Sound Recording Advice
Besides covering acoustics in very readable detail, this book
is geared towards the do-it-yourselfers. Example studio
equipment setups are given for various budgets and there are
literally hundreds of great Internet references. This book
should be within reaching distance in your studio at all times!
Read more about this book...
News & Notes
Modern Recording Techniques (1 of 3) [10/3/04 12:38:05 AM]
Auralex Acoustics - Auralex Book Referrals Page.
Auralex Newsletter
Mr. Huber is very well known for his easy-to-read primers on
studios, recording, MIDI, etc. This book is no exception.
Sections cover the gamut from miking techniques to room
acoustics. A great read!
Read more about this book...
Studio Monitoring Design: A Personal View
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Almost everyone that works for Auralex is required to read
the Control Room acoustics sections of this book. Mr. Newell's
discussions of "Hidley" rooms and neutral Control Room
acoustics are fantastic. Also, this book is a great resource for
amateur (and professional) studio loudspeaker builders.
Read more about this book...
Recording Spaces
Another Newell classic. The discussions on "natural" live
rooms and the case studies cited throughout are very helpful
and insightful.
Read more about this book...
Project Studios: A More Professional Approach (2 of 3) [10/3/04 12:38:05 AM]
Auralex Acoustics - Auralex Book Referrals Page.
This book goes into a lot of detail on how the "Project" studio
is currently being redefined. Lots of informative discussions
on acoustics, cabling, pro vs. consumer equipment, etc. It
seems like anything Mr. Newell writes is destined to be a
Read more about this book...
Sound Sytem Engineering
With this book, we're really getting into the "heavies."
Definitely not for the "mathematically challenged." However,
if you are a systems designer, installer or work quite a bit
with different (large and small) room/loudspeaker interface
problems, this book is your bible.
Read more about this book...
Handbook for Sound Engineers, Third Edition
Again, this book is definitely more technical, more "textbook."
At a whopping 1,553 pages, it is definitely not "light" reading.
With contributions from many audio industry experts
(including Auralex Chief Engineer, Jeff Szymanski), this is the
book to read to understand everything about everything in
the audio world.
Read more about this book...
© Copyright 2004 Auralex Acoustics, Inc. (3 of 3) [10/3/04 12:38:05 AM]
Auralex Acoustics - Frequently Asked Questions - General Acoustics Answers
Auralex Acosutics - Menu for frequently asked questions on acoustics.
Site Search
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Question #13
What's an STC?
STC stands for ''Sound Transmission Class.'' This is a single-number rating that
can be used to compare the acoustical isolation of different barrier materials or
partition constructions. The method used to determine the STC of a material or
partition type is complicated. The following is a basic description of the methods
covered in much more detail in ASTM E413:
The method to determine STC is conducted using two test rooms: a ''source'' room
and a ''receiver'' room. The source room will contain a full-range test loudspeaker.
The receiver room will contain a microphone, which is connected to soundmeasuring devices. There is a nominal opening between the two rooms - usually
about 9' wide by 8' high, but can vary in accordance with the standard.
The first step is to measure the sound transmitted from one room into the other
through the opening. The sound is measured in decibels (dB) in 1/3-octave bands
from 125 Hz to 4000 Hz.
The next step is to ''plug'' the opening with the material or partition construction.
This could be a single layer of barrier (such as plywood or SheetBlok), or a
complete wall with as many materials, layers, air gaps, etc. that can fit in the
opening. The edges are completely sealed and sound transmission between the
rooms is measured again.
News & Notes
The sound level from the ''after'' test is subtracted from the sound level ''before''
plugging the opening. The resulting difference is the transmission loss or ''TL.''
Next, the TL is plotted on a graph of 1/3-octave band center frequency versus
level (in dB). Now this is where it can get confusing. To get the STC, the measured
curve is compared to a reference STC curve. (For an exact definition of the
reference curve, see ASTM E413 or the third edition of the Handbook for Sound
Engineers, edited by Glen Ballou - Chapter 3, ''Acoustical Noise Control.'') Two
criteria are used to ''match'' the curves:
1. The reference curve shall not exceed the measured TL by more than 8 dB in
any 1/3 octave band, and (1 of 3) [10/3/04 12:40:35 AM]
Auralex Acoustics - Frequently Asked Questions - General Acoustics Answers
Auralex Newsletter
2. The sum of all the ''negative discrepancies'' shall not exceed 32.
This actually sounds more complicated than it is. A simple spreadsheet can be
used to calculate the STC for any range of TL values.
Once the two above criteria are met, the value of the reference curve at 500 Hz is
read as the ''STC'' of the material or partition type.
So, what does the STC actually tell us about a material or partition? Very little.
Just as NRCs don't tell much about the specific absorption properties of a material,
STC tells very little about the isolation properties. It is always better to compare
the actual TL values in different octave or 1/3-octave bands to get a better idea of
the performance of one barrier or partition versus another. Just as different
materials with the same NRC can have different performances, different materials
with the same STC can behave very differently. Here is a table of two sets of TL
data that yield the same STC:
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125 Hz
250 Hz
500 Hz
1000 Hz
2000 Hz
4000 Hz
As you can see, the performance at low frequencies is dramatically different, yet
the two materials or partitions have identical STCs.
A direct result of this is that many building materials have similar STCs - ½''
drywall, ½'' plywood, SheetBlok, etc. are all around STC-26 or STC-27. However,
the performance of the SheetBlok - a ''limp-mass'' barrier is significantly better at
low frequencies. This is something you cannot compare using STCs - you have to
look at the performance in octave bands.
Anyway, the STCs for a multitude of materials (barrier, as well as doors, windows,
etc.) and constructions types (walls, ceilings and floors) have been tested over the
years. If you cannot find the STC of a construction type, contact us to find out
what you should build to get the isolation you need.
One important thing to note about STCs is that they do not add. At all. In theory,
the STCs of two barriers that are identical in every way can be combined and see
an increase of 6 in STC. (This is an extension of the mass law to STCs - doubling
the mass theoretically improves TL by 6dB.) But this is rarely what ''really
happens.'' Two dissimilar barriers or partitions would have to be tested together to
absolutely determine the new STC. Spreadsheets can be used to predict the
performance of combinations using the TL data from the two separate materials or
partitions. However, since these predictions often use the mass law, the
predictions are rarely realized in the field.
To finish this section off, we'll leave you with some STCs and their ''subjective''
ratings. (Note: Some people are more sensitive than others. It is completely
possible that an STC-50 partition may not be enough for someone who is
hypersensitive to noise in their environment.)
STC 25-35 Conversation can generally be heard and understood through
material/partition. Examples: Hollow-core wood door, one layer of drywall on each
side of studs with no insulation.
STC 35-45 Conversation can generally be heard, but not understood through
material/partition. Examples: Solid-core wood door, one layer of drywall on each (2 of 3) [10/3/04 12:40:35 AM]
Auralex Acoustics - Frequently Asked Questions - General Acoustics Answers
side of studs with insulation.
STC 45-55 Conversation can neither be heard nor understood. Loud sources such
as stereos or machinery can still be heard. (Minimum acceptable STC for studio
partitions.) Examples: Acoustical doors (,, staggered stud construction, RC8 Resilient Channel on
single stud partitions, 6'' concrete block (painted).
STC 55-65 Most noise sources rendered inaudible. Loud sources may still be
sensed. (Recommended for studios.) Examples: Double door ''airlocks'',
combination concrete block and stud/drywall partitions (double walls), double stud
walls with decoupled air cavities.
STC 65+ Considered ''silent'' by most observers. Desirable design criteria for
severely noise sensitive spaces (e.g., studios). Examples: Double concrete block
walls, massive double stud walls with larger (6''+) air cavities.
Note: STCs are laboratory measurements. Some losses take place when the
material or construction is implemented in the field. Due to these losses, the ''Field
Sound Transmission Class'' or ''FSTC'' aka the ''Noise Isolation Class'' or ''NIC,'' is
usually 5 - 10 lower than the laboratory STC for the same material or
construction. This should be noted when choosing a construction or material for
implementation in the field.
© Copyright 2004 Auralex Acoustics, Inc. (3 of 3) [10/3/04 12:40:35 AM]
Auralex Acoustical Testing Data Master Table
Other Tests
Absorption Data in Accordance with ASTM C423
Auralex Product
1/3-Octave Band Center Frequency (Hz)
Auralex Product
SheetBlok STL (dB)
1" Studiofoam Wedges
2" Studiofoam Wedges
3" Studiofoam Wedges
4" Studiofoam Wedges
2" Studiofoam Pyramids
4" Studiofoam Pyramids
2" Studiofoam Metro
4" Studiofoam Metro
2" Sonomatt
2" Wedgies
MAX-Pak Studiofoam Wedges
MAX-Wall Panels 01
MAX-Wall Panels 02
MegaMAX-Wall Panels 01
MegaMAX-Wall Panels 02
Venus Bass Traps
LENRD Bass Traps
Metro LENRD Bass Traps
TruTraps no TruSpacers
TruTraps with TruSpacers
Sunburst Male
Sunburst Female
VersaTile Convex
VersaTile Concave
VersaTile Corner
2" SonoFlats
M-111 Tiles
B24/X24 Panels
ELiTE Absorber
2" Mineral Fiber
4" Mineral Fiber
T'Fusor 01
T'Fusor 02
800 10001 1250 1600 20001
0.10 0.10 0.13 0.16 0.20 0.30 0.43 0.59 0.68 0.77 0.85 0.94
0.16 0.24 0.30 0.45 0.64 0.91 1.01 1.06 1.05 1.02 1.03 0.99
0.19 0.31 0.49 0.71 0.87 1.06 1.10 1.05 1.04 1.03 0.97 0.96
0.36 0.62 0.85 1.09 1.21 1.25 1.17 1.16 1.14 1.08 1.06 1.06
0.09 0.13 0.18 0.27 0.34 0.57 0.73 0.90 0.96 1.05 1.07 1.03
0.28 0.37 0.50 0.70 0.85 1.01 1.09 1.13 1.13 1.13 1.12 1.11
0.09 0.18 0.23 0.35 0.47 0.68 0.82 0.90 0.93 0.96 0.92 0.91
0.40 0.56 0.72 0.98 1.13 1.19 1.23 1.24 1.26 1.26 1.24 1.22
0.14 0.20 0.27 0.35 0.47 0.62 0.75 0.85 0.92 0.96 1.01 1.02
0.10 0.19 0.21 0.36 0.45 0.70 0.90 0.99 0.99 1.05 1.05 1.05
0.14 0.22 0.27 0.36 0.43 0.54 0.62 0.68 0.71 0.76 0.80 0.83
0.18 0.23 0.29 0.41 0.49 0.57 0.66 0.72 0.75 0.78 0.84 0.90
0.12 0.16 0.22 0.30 0.35 0.47 0.55 0.65 0.66 0.71 0.74 0.81
0.86 1.06 1.02 1.11 1.06 1.06 1.07 1.05 1.05 1.05 1.05 1.02
6.05 6.46 7.28 9.31 10.62 11.98 13.06 13.70 14.32 14.12 14.06 13.70
1.20 1.32 1.17 1.19 1.16 1.17 1.09 1.11 1.08 1.08 1.05 1.07
10.18 11.68 12.68 15.04 16.24 17.44 17.75 17.63 17.42 17.49 17.08 16.81
1.30 1.31 1.34 1.32 1.36 1.29 1.25 1.25 1.26 1.20 1.22 1.25
1.11 1.28 1.28 1.39 1.45 1.45 1.45 1.39 1.39 1.32 1.30 1.27
1.05 1.23 1.15 1.18 1.22 1.28 1.25 1.25 1.20 1.16 1.14 1.15
0.46 0.65 0.82 1.06 1.18 1.24 1.26 1.25 1.21 1.22 1.20 1.22
0.68 0.88 1.01 1.25 1.40 1.41 1.37 1.30 1.22 1.25 1.30 1.29
0.96 1.15 1.23 1.22 1.21 1.14 1.12 1.09 1.07 1.05 1.05 1.05
0.60 0.84 1.02 1.08 1.06 1.00 1.01 1.06 1.08 1.05 1.04 1.05
0.27 0.34 0.48 0.67 0.75 0.84 0.84 0.84 0.80 0.84 0.86 0.90
0.36 0.38 0.52 0.67 0.74 0.90 0.92 0.91 0.92 0.91 0.90 0.92
0.85 0.88 1.01 0.99 0.95 0.99 1.05 1.10 1.12 1.13 1.11 1.13
0.28 0.36 0.46 0.69 0.85 0.99 1.07 1.12 1.12 1.15 1.12 1.14
1.21 1.41 1.36 1.46 1.50 1.50 1.46 1.41 1.38 1.37 1.36 1.34
0.14 0.21 0.25 0.44 0.59 0.73 0.82 0.87 0.91 0.97 0.96 0.97
0.12 0.19 0.20 0.42 0.54 0.72 0.84 0.93 0.97 1.02 1.04 1.04
0.11 0.22 0.29 0.36 0.48 0.80 0.92 0.94 1.01 1.03 1.02 1.05
1.01 1.09 1.10 1.26 1.35 1.39 1.42 1.36 1.35 1.34 1.31 1.33
0.58 0.60 0.39 0.14 0.27 0.23 0.18 0.18 0.10 0.08 0.09 0.09
0.40 0.30 0.31 0.25 0.25 0.23 0.22 0.21 0.16 0.14 0.14 0.15
0.05 0.07 0.05 0.05 0.08 0.14 0.19 0.25 0.36 0.57 0.66 0.68
2500 3150 40001
1.01 1.03 1.00
0.97 0.95 1.00
0.98 1.01 1.05
1.11 1.09 1.09
0.98 0.96 0.98
1.12 1.09 1.12
0.89 0.87 0.89
1.20 1.19 1.20
1.00 1.02 1.02
1.01 1.03 1.05
0.85 0.89 0.99
0.91 0.94 1.00
0.87 0.93 1.01
1.00 1.00 1.02
13.57 13.25 13.22
1.04 1.03 1.02
16.76 16.48 16.41
1.21 1.18 1.20
1.26 1.27 1.31
1.13 1.10 1.12
1.21 1.15 1.13
1.28 1.27 1.31
1.07 1.04 1.08
1.06 1.08 1.08
0.94 0.97 0.99
0.99 1.01 1.00
1.14 1.14 1.17
1.14 1.13 1.13
1.32 1.31 1.33
0.98 0.99 0.99
1.04 1.02 1.01
1.03 1.00 0.99
1.28 1.25 1.24
0.09 0.07 0.07
0.16 0.18 0.21
0.60 0.55 0.47
PlatFoam/GRAMMA Maximum Impact STL (dB)***
TruTraps with Spacers—Special
12.13 14.02 15.00 14.91 13.77 13.77 13.79 14.23 14.33 14.66 14.13 14.26 14.29
T'Fusor Diffusion Coefficients
2'x4'x1" Foam Panel
2'x4'x2" Foam Panel
2'x4'x3" Foam Panel
2'x4'x4" Foam Panel
2'x4'x2" Foam Panel
2'x4'x4" Foam Panel
2'x4'x2" Foam Panel
2'x4'x4" Foam Panel
4'x8'x2" Foam Panel
1'x1'x2" Foam Tile
1'x1'x2"/4'x2'x2" Foam Tile/Panel
1'x1'x2"/2'x4''x2" Foam Tile/Panel
2'x4'x1.5" Foam Panel
20"x48" Stand-mounted Panel
20"x48" Stand-mounted Panel
24"x48" Stand-mounted Panel
24"x48" Stand-mounted Panel
2'x4'x12" Foam Panel
2'x1'x1' Triangular Foam Bass Trap
2'x1'x1' Triangular Foam Bass Trap
2'x4'x3" Foam Panel
2'x4'x3" Foam Panel on 3" spacers
4'x1' Semi-cylindrical Foam Absorber
4'x1' Concave Foam Absorber
24"x16"X2" Foam Panel
24"x16"X2" Foam Panel
24"x16"X2" Foam Panel
2'x2'x2" Flat, beveled Foam Panel
4'x1'x6" Foam Column Absorber
1'x1'x2" Melamine tiles
2'x2'x1" Natural fiber panel (no facing)
2'x4'x1" 6# FG panel with fabric facing
4'x1'x6" Column Absorber with fabric facing
1" Natural fiber core with fabric facing
2'x4'x2" Mineral fiber panel (no facing)
2'x4'x2" Mineral fiber panel (no facing)
23.75"x23.75" Diffusor panel
23.75"x23.75" Diffusor panel
23.75"x23.75" Diffusor panel
1/8" thick EVA barrier material
Values reported as octave-band absorption coefficients in accordance with ASTM C423.
MAX-Wall and MegaMAX-Wall tested free standing in chamber per Section 12.1.4 of ASTM C423. Values reported in each band are sabins per unit.
Data also approximate absorptive effect of DST-Rs, Q'Fusors and ProFusors
Estimated - Partial area of chamber floor floated using PlatFoam to mimic real world conditions. Not in strict compliance with ASTM E492.
Panels were mounted on spacers, but not placed in the official test area. They were spread out in the lab to mimic a competitor's placement of a similar device. Absorption values are sabins/unit.
This table was last updated on:
ASTM E4924 2"x4"x48" Isolating foam
2'x4'x3" Foam Panels on 3" spacers; panels
ASTM C4235
spread out on the chamber floor
AES-4id-2001 23.75"x23.75" Diffusor panel
Auralex Acoustics - Frequently Asked Questions - General Acoustics Answers
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Question #10
What is an NRC?
NRC stands for Noise Reduction Coefficient. The method by which NRC is
ultimately obtained can be: the Reverberation Room Method (ASTM C423) or the
Impedance Tube Method (ASTM C384). The Reverberation Room Method is the
more popular of the two in terms of tests conducted on acoustical room
treatments. How this method works: Approximately 72 square feet (or more, but
not less) of material is placed on the floor of a Reverberation Chamber - a big
room with (usually) all hard, concrete surfaces (the opposite of an ''Anechoic''
Chamber - a room with no echoes) - and the change in absorption from the empty
room to the room with the treatment area on the floor is measured. A kind of
''Before and After'' test.
The final result of the calculations is reported as Sabine absorption coefficients
(''Sabine alphas'' or ''aSAB'') in octave bands from 125 Hz to 4000 Hz. For a
convenient, single-number rating, the Sabine alphas for 250, 500, 1000 and 2000
Hz are averaged and the result is the Noise Reduction Coefficient, or NRC. The
alphas in the individual octave bands are interpreted as the relative sound
absorbed over the octave band range. The higher the number, the more sound is
Those of you who are math savvy will notice right away that an NRC doesn't tell
you much. Take a look at the following two columns of alphas with the same NRC:
News & Notes
250 Hz:
500 Hz:
1000 Hz:
2000 Hz:
*In accordance with standards, NRCs are rounded off to the nearest 0.05.
These two materials have identical NRCs, but do not perform identically in
individual bands. If you want to get an idea of how an acoustical material actually
performs, look at the alphas in the individual bands. If you want to get ''in the
ballpark,'' then you may find the NRC useful. NRCs are handy when comparing
materials side-by-side, but only to a point. For example, drywall has an NRC of (1 of 3) [10/3/04 12:44:49 AM]
Auralex Acoustics - Frequently Asked Questions - General Acoustics Answers
Auralex Newsletter
about 0.20 and 2'' Studiofoam NRC is 0.80. Obviously, the Studiofoam is better at
absorbing sound. On the other hand, 2'' Studiofoam and 1'', 6# fiberglass both
have NRCs of 0.80, but the alphas in different bands are not the same.
Some other useful absorption coefficient and NRC information:
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• The ASTM C423 standard makes it possible to arrive at absorption coefficients
and, therefore, NRCs that are greater than 1.00. This may be counterintuitive
since many references define the Sabine alpha and NRC as the ''percentage of
sound absorbed'' by a material. This treatment of alphas and NRCs as
percentages, however, is not really accurate. The formulae used in the standard to
measure absorption are dependent on: the decay of sound in the test room, room
volume, room temperature and the area of Chamber floor covered by the test
material. ''Sabine absorption'' and ''Sabine alphas'' come from the fact that the
absorption is calculated using the Sabine equation. Nowhere in the ASTM C423
standard is there a reference to Sabine alphas being equal to percentages of any
kind. Therefore, numbers greater than 1.00 are possible. This means that Sabine
alphas are simply a representation of the relative amount of sound absorbed by
the material. (Relative to the absorption without treatment in the room.) Higher
numbers mean more absorption in that frequency band.
[For more on this, please see The Sabines at Riverbank by John Kopec. Also, the
absorption coefficient, or alpha, of a material is sometimes calculated using the
difference between incident and reflected sound intensity divided by the incident
sound intensity. In other words, a percentage. Care should be taken not to equate
this alpha with the Sabine alpha described above (We have made this mistake
ourselves in the past!), as they illustrate two different properties. This may be the
source of some of the confusion about absorption coefficients.]
• Alphas measured in the lab are going to be different from those measured in a
''real'' room. However, using the alphas to predict the acoustics of a (usually
large) room will get fairly good results. Predicted effects at low frequencies are
usually the most ''different'' from real world measurements because, in general,
the uncertainty of the lab measurements increases as frequency decreases.
• Alphas calculated using Sabine's method are only completely valid to predict the
acoustics in large, reverberant spaces using the Sabine formula. Other formulae
are available for different initial conditions (i.e., how the room starts out - volume,
surface types, etc.), but using Sabine alphas in these equations is not purely
• Small rooms cannot be considered ''reverberant'' in the true sense of the term even with all hard surfaces. There is simply not enough volume in the room to
consider this so. Instead, using absorbers for the treatment of early reflections,
flutter echoes and ''room ring'' is more appropriate. Placement is usually by
experience and using techniques such as the mirror trick referenced earlier.
Note: Auralex does not use the Sabine equation to predict small room acoustics.
• The method of mounting used for the test specimen in the reverberation
chamber can affect the numbers. Most materials for treatment of walls or ceiling
are tested using what is called an ''A'' mounting. Type ''A'' mounting means the
test specimen was laid directly on the chamber floor. Ceiling tiles are often tested
using an ''E400'' mounting. The ''E'' designates a sealed air space behind the
specimen and the number after the ''E'' is the depth of the airspace in millimeters.
Other mounting methods are available (''B'', ''D'', etc.), but are rarely used. (See
ASTM E795 for more information.)
• The best way to use NRCs and alphas provided by Auralex and other companies
is to compare performance of products. Be careful, though. Oftentimes, NRCs are
used as marketing tools. Be wary of companies that offer absorption coefficients
and NRCs without references to standards and mounting methods. All Auralex
absorption products, unless otherwise indicated, are measured in accordance with
ASTM C423 using Type ''A'' mounting (see above). Direct comparisons to (2 of 3) [10/3/04 12:44:49 AM]
Auralex Acoustics - Frequently Asked Questions - General Acoustics Answers
competitors and other materials can only be made if their testing methods are the
• The thickness (normal and angular) of an absorber does limit its low frequency
performance. However, the low frequency performance of panel absorbers might
be better than other audio ''experts'' have led you to believe. Often, the
limitations of low frequency performance is described as a function of the
thickness of the material versus the ¼-wavelength of the lowest frequency that is
affected by the material. In other words, if a material is 4'' thick, that corresponds
to a low frequency cut-off of:
f = low frequency cutoff (Hz)
c = speed of sound in air (usually about 1130 ft/sec)
t = thickness of absorber (ft)
This is misleading. This would be valid if the panel was only placed at normal
incidence to a sound source. ''Normal incidence'' means at 0°. A loudspeaker
facing parallel to a wall would be considered normal incidence. When was the last
time you saw this in a control room? Usually, walls, and hence absorbers, are
placed at different angles to the sound source. The angular incidence of the sound
on the panel increases the absorbers effective depth. Click here for an illustration.
Therefore, lower cutoff frequencies are achievable. To use the earlier example,
this is the direct cause of absorption values for 4'' materials below 850 Hz - the
supposed low frequency cutoff for normal incidence. The bottom line: Absorbers
such as 4'' Studiofoam, Sunbursts, MAX-Wall, LENRDs, Venus Bass Traps, etc. can
all absorb low frequency energy. Feel free to contact us to find out which one is
right for you!
To purchase ASTM standards (or simply browse abstracts of the standards), please
© Copyright 2004 Auralex Acoustics, Inc. (3 of 3) [10/3/04 12:44:49 AM]
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Auralex's RC8 Resilient Channel is a
specially-formed, sturdy metal device that,
when used to hang drywall (instead of just
attaching the drywall to the studs or joists),
GREATLY improves the sound transmission
characteristics of the wall or ceiling system.
RC8 should be installed horizontally at the
bottom and top of your wall, then every 2' or
less in between. Up to (2) layers of 5/8"
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on RC8, even on a ceiling.
RC8 is available in handy 8' lengths that
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Resilient Channel Discussion
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and up.
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Walls and ceiling, ceiling
and walls…RC-8 resilient
channel is installed and
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© Copyright 2004 Auralex Acoustics, Inc. (2 of 2) [10/3/04 12:53:52 AM]
Subject: Quiet Dimmers?
Date: Tue, 9 Jul 2002 11:34:30 -0500
Can anyone provide me with a source for silent lighting dimmers? This is something our customers ask for a lot.
(Note: Silent in terms of: You've used them and know they're silent. This is preferred to: The company that makes
them claims their silent :-)
Any help is much appreciated!
Best regards,
Jeff D. Szymanski, P.E.
Chief Acoustical Engineer
Auralex Acoustics, Inc.
Subject: Re: Quiet Dimmers?
Date: Tue, 9 Jul 2002 11:44:12 -0500
You are looking for the dimmer switch that replaces the wall light switch as opposed to a lighting system? If so let me
know when you find one!
Bennett Brashier
E-Court Coordinator
Subject: RE: Quiet Dimmers?
Date: Tue, 9 Jul 2002 12:06:25 -0500
Any wall-mount architectural dimmer with at least 400 microsecond rise time (the higher the number, the better)
should be fine. ETC, Leprecon, Leviton/NSI, strand, Lutron, etc. These will NOT fit in a handy box. They must be
remotely mounted, usually near a circuit breaker panel.
For a 2000 Watt dimmer, mounted in a 4-square box, you could add a 20 Amp choke (in series with the output lead) in
an adjacent 4-square box if code allows.
Dave Tipton
Tipton Sound & Lighting
Subject: RE: Quiet Dimmers?
Date: Tue, 9 Jul 2002 12:24:38 -0500
You are actually looking for a quiet dimmer/lamp combo. In a concert hall or critical theatre situation, we look for 800
microsecond rise time house dimmers. I've seen folks get lucky with 500microseconds (but I've also seen 'em burned
with the wrong lamp). If you are really critical, it's best to try out a number of dimmer/lamp combinations.
Guessing that Jeff's clients are just looking for studio track lighting type dimmers, they might be looking for luxtrol
autotransformers. Again, requires oversize bos and sometimes requires resilient mounting.
I've seen a few quiet installations of a Lutron LDC units, has anyone run into a noisy LDC system. Typically looking at
NC-15 type spaces.
Date: Tue, 09 Jul 2002 13:30:42 -0400
Subject: RE: Quiet Dimmers?
If you are talking about physical noise rather that electrical, remember that the filaments in stage lights can sing in
response to the fast rise at that start of the switch cycle. This noise is dependant on the lamp type as much as the
Subject: RE: Quiet Dimmers?
Date: Tue, 9 Jul 2002 13:51:31 -0400
We undertook a study of dimmers from the majors a few years ago that led us to the conclusion that rise time is only
one minor element in the equation.
That said if you are looking at a lighting system - high rise time is helpful - 500ms or more from a major manufacturer ETC, Colotran, Strand, Entertainment Technology. The reality is that a 500ms choke in one dimmer manufacturer's
product will perform differently in another manufacturer's product.
An even better choice is Entertainment Technology Dimmer which doesn't really have a rise time, it has a fall time
which means the filaments aren't jerked around as much - therefore are much quieter for it's nominal rise time. It uses
IGBT instead of SCRs.
The lamp is actually more critical. You want something with a short, well supported filament. No PAR 64s, no A
The reflector on the lamp is also a significant factor as it tends to focus sound as well as light.
Some of my colleagues have also found that a high impedance power supply to the dimmer also helps. People has
gone as far to run wire in a raceway where it can be frequently strapped down to avoid mechanical vibration from the
If it is a wall dimmer you are looking for, there are actually autotransformer dimmers out there. They are silent. They
are also big and hot.
Curtis Kasefang
Public Assembly Consultants
Date: Tue, 09 Jul 2002 12:35:09 -0600
Subject: Re: Quiet Dimmers?
Of course I remember when every decent recording studio used Variac power transformers for dimmers. Not very
practical, may not even be legal now I suppose. But they were quiet. And that massive phenolic knob looked so
-Best regards,
Andrew Smith
Date: Tue, 09 Jul 2002 10:51:21 -0400
Subject: Re: Quiet Dimmers?
"Jeff D. Szymanski" wrote:
> Can anyone provide me with a source for silent lighting dimmers?
Silent --- is relative. Noise factors in the lighting circuit also involve the total load on the circuit and ratings can be
manipulated to give a false specification. The rise time as measured in microseconds needs to be from 10% to 90%
of the leading edge of the sine wave and not 0% to 100%, and under full rated output power . Underrated loads will
show marked improvement of sine wave conditions. Full load is worst case. At least some of the better manufacturers
rate their dimmers this way and specify it as such.
In much the same way as amplifiers are matched to the speaker load for a given design and not the other way
around, I recommend that any application for the lighting zone be defined first then look at what dimmer approach
might have the best performance for the application.
Cheap wall triac dimmers should be avoided at all costs
A remote control system similar to what Crestron or AMX produce would be a better way of moving the acoustically
noisy dimmer to the garage or closet and add an additional rated toroid to the main feed to increase the rise time
of the critical dimmer. (if required, based on total load requirements, your mileage will vary).
Once the chokes beat the wanna be square back into resembling a sine wave, the filaments of the Halogen lamps
should be pretty quiet and the mechanical noise of the toroids and SCR packs are out of harms (ears) way.
Details and design are the best approach vs. experimenting and frustration. It doesn't have to be that hard to solve the
problem. If someone is willing to invest in their home theatre or studio the kinds of samoleans that are required to do it
right, why would anyone on this list leave the critical noise generator from Hell up to the local electrician or the owners
trip to the electrical department at Home Depot.
Add the lighting design to your bag of services and don't let the other trades diminish our best efforts of incredibly
quiet sound systems and rooms.
Hot topic, good timing.
John Malek
Date: Tue, 9 Jul 2002 22:15:30 +0200
Subject: Re^2: Quiet Dimmers?
> If you are talking about physical noise rather that
> electrical, remember that the filaments in stage
> lights can sing in response to the fast rise at
> that start of the switch cycle.
well said, Steve! I can remember an installation back at my university days, where audible hum was a problem
after everything was built and set up. After recommending to use audio transformers to break up ground connections
between different parts of the installation and to again carefully check grounding an shielding, we finally suggested
to switch the system off just to see what happened:
... still humming ... same reason Steve mentioned:
The lighting system was on but dimmed and the filaments of the lamps produced (very) audible hum.
Best regards,
Dieter Michel
Subject: RE: Quiet Dimmers?
Date: Tue, 9 Jul 2002 23:36:32 -0400
Many valid replies to this topic. I'll add a few additional....
For recording studios, etc., there is really only one logical choice: autotransformers.
Less critical, but still demanding, apps:
Wall switch/dimmer replacement: Lutron NOVA series works pretty well in non-crit. apps. Get a sample from your
Lutron rep and try it.
Remote solid-state dimmers: Typically come in 350/500/800 micro-sec. Rise time variants (or similar). In general, 350
works OK in Theatre, 500 for more critical Theatre and Live apps, and 800 for TV production (as recommended by the
manufacturers and consultants). (Personally, I've never done a job that needed 800's, and I have done a few TV
studio packages, but no really large ones.) Older fixtures, which use older lamps, typically have larger, less rigid
filament assemblies. The newer, compact, high-output lamps typically have smaller filaments with tighter support, and
are much less likely to buzz/vibrate. Ever listen to a 1500W, mogul-base, PS-52 incandescent lamp sing in an old TV
If dimming fluorescents, ALWAYS use hi-perf. solid-state ballasts. IMO, the only ones to use are Lutron Hi-Lume
(1%). A logical extension would be that the best way to control a Lutrom ballast would be with a Lutron dimmer
If dimming LV fixtures, do NOT use fixtures with magnetic transformers unless you are very sure you know what you
are doing (derating, etc.) Solid-state transformers are available. (Seen a lot of flamed-out LV Pinspots in my lifetime.)
An interesting approach Crown used to use at trade shows was to run lights off of Power Amps. Wouldn't likely pass
code though <gr>. Didn't make any noise!
There "was" a dimmer designed around Power MOSFET's, which was essentially an amplifier, but it was a prototype
that was shown but then never made it to market (I don't think).
The "gate turn off" dimmers, like Entertainment Technology, do indeed make less "noise", but there are power
limitations to the design, unless this has changed since the last time I looked. GTO power devices are apparently
harder to produce.
Often, the noisiest part of a remote dimmer rack is the high-velocity cooling fan/s. When the big mfrs. wanted to put
higher-density dimmer racks together in smaller spaces, they had to increase velocity to get similar cooling. There
are a few dimmer systems on the market that are still convection-cooled, eliminating this issue.
Among the first "electrical dimmers" was the Salt-Barrel Dimmer. If you didn't electrocute yourself, it would have
provided "noise-free" dimming (except for the occasional "slosh"!)
<Private message>
Hi Jeff,
How quiet?...
Before I left American Audio, we were using ETC dimming. It was in fact very quiet for auditorium, choir applications.
No ringing elements etc. But for studio work, you might consider a medical grade adjustable autoformer type. (two
windings one inside the other and voltage change occurs as you turn the winding out of alignment with the field) I
can't remember the manufacturer, but I used them on a job about 10 yrs ago. Obviously for incandescent loads
Hope you are well. We are.
Jim Young
And from adrianh at
OK you have now crossed into my world.
To do it right you need a motorized VARIAC which is a (variable AC transformer) VARIAC is a trade name. The two
big guys in this industry are.
Staco Energy
Superior Electric see their POWERSTAT® line
These guys have a nice page with info and pictures.
Their prices are steep!
The motorized will allow you to control the dimming level from a remote location. For most of us a standard VARIAC
mounted on the wall will work just fine.
Newark has a good selection.
This Staco unit Newark part# 17C6451
Would work for loads 500watts and below.
These transformers do make a little acoustic noise about the level of a whisper and need some air to keep them cool.
Also they are a transformer and they WILL radiate a magnetic field so keep sensitive electronics away. Hint mount in
a NEMA 1 type of box (steel) your electrician will know about this.
The thing they do best is give you clean AC out as clean as it was coming into your studio. It does not use any noise
switching circuits so it gives you clean power to your load.
Be sure to follow all building electrical codes when installing them and ensure your loads will be happy with reduced
voltages. Incandescent and Halogen lamps are very happy with this. Other lamps with ballasts consult the
manufacturer if the lamps can be dimmed.
Go to your local surplus store or Hamfest. I have paid no more than $25 for my biggest hand turn unit. The motorized
units do not show up too often on the used market.
These puppies are expensive for large studios.
I had a friend give me a 15A motorized and that is what I am using in my studio. The unit is mounted in an electrical
closet in a steel NEMA 1 enclosure. It does buzz acoustically (motor) as it is turning but that only happens when I
raise or lower the lights. I did not discuss distance I assume if you put the VARIAC in a steel enclosue NEMA #1
(standard electrical enclosure) You will be fine even with guitar pickups 10 feet away. Any closer I would be nervious.
Basically it is a variable transformer that allows you to adjust the incoming voltage from 0 through 120VAC. Since it
allows you to adjust to any voltage between the incoming line voltage and zero it allows you to set the lamp to any
Adrian Howell
Application Notes, Papers and Magazine Articles
Application Notes
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(Adobe Acrobat Reader Version Information)
Jensen System Troubleshooting Guide
(115KB PDF)
Bill Whitlock
Some Tips on Stabilizing Op-Amps
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Deane Jensen
Answers to Common Questions about Audio Transformers
(33KB PDF)
Bill Whitlock
Interconnection of Balanced and Unbalanced Equipment
(59KB PDF)
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Hum & Buzz in Unbalanced Interconnect Systems
(94KB PDF)
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Theory and Construction of Mic "Splitters"
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AES Papers
(Information about obtaining Jensen AES Papers)
JE-990 Discrete Operational Amplifier
Deane Jensen
(AES Journal)
High Frequency Phase Specifications - Useful or Misleading?
Deane Jensen
(AES Preprint) (1 of 2) [10/3/04 1:24:51 AM]
Spectral Contamination Measurement
Deane Jensen/
Gary Sokolich
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Balanced Lines in Audio Fact, Fiction and Transformers
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A New Balanced Audio Input Circuit for Maximum Common-Mode Rejection in
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Subtleties count in wide dynamic range analog interfaces
EDN 1998 Issue 12 June 4th
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VENUS Bass Traps - Low frequency sound control products from Auralex Acoustics.
Auralex Acoustics - Menu for low frequency sound control products.
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NRC: 1.30 Qty: 2 (16 sq. ft.);
Adhesive Per Box: Foamtak or 2
The Venus Bass Trap achieves a prodigious
level of low frequency sound control at your
room boundaries, where low frequency
problems begin, at a price that allows it to fit
into most budgets. Venus Bass Traps ship in a
2'x4'x12" size, but is often cut in half to 2'x2',
then paired with a 12" Auralex CornerFill, as
shown in the diagram below.
While the Venus Bass Trap can provide serious
low frequency sound control and broad
bandwidth absorption that's literally second to
none in all rooms, it really shines in larger
rooms like gymnasiums, houses of worship
and multipurpose rooms.
Available Colors
News & Notes
Forest Green Kelly Green
(Due to the variance of different computer monitors and video card
color depth, Auralex Acoustics cannot guarantee that the color(s)
represented on your computer screen will exactly match the foam
products shipped. These color swatches are for reference purposes
only.) (1 of 2) [10/3/04 1:30:37 AM]
VENUS Bass Traps - Low frequency sound control products from Auralex Acoustics.
Auralex Newsletter
Application Photos
Teal VENUS bass traps
are shown creating a
significant bass trap
under the shelf of the
audio demo room of
IRC Audio.
A full, 2’x4’ VENUS
bass trap is installed
in the corner of this
control room, while
quartered segments of
VENUS are used to
border the wall ceiling
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This rendering shows
how half-segments of
VENUS bass traps can
be combined with 12”
CornerFills to span a
corner junction.
Acoustically, this
presentation is “top
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© Copyright 2004 Auralex Acoustics, Inc. (2 of 2) [10/3/04 1:30:37 AM]
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Book Description
Philip Newell's comprehensive reference work contains pearls of wisdom which anyone involved in sound recording
will want to apply to their own studio design. He discusses the fundamentals of good studio acoustics and monitoring
in an exhaustive yet accessible manner.
Recording Studio Design covers the basic principles, their application in practical circumstances, and the reasons for
their importance to the daily success of recording studios. All issues are approached from the premise that most
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Because of the importance of good acoustics to the success of most studios, and because of the financial burden
which failure may impose, getting things right first time is essential. The advice contained in Recording Studio
Design offers workable ways to improve the success rate of any studio, large or small.
*A comprehensive overview of the principles of recording studio design and their practical application
*Improve the potential of your studio with expert advice on design and monitoring
*Complex issues are explained in accessible language and illustrated with examples from actual studios
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Auralex Acoustics - The Auralexian!
Auralex Acoustics - The Auralexian!
Site Search
Featured Products
Given the common concerns faced by the typical Auralex customer, insights can
certainly be gained through the experiences of those who have completed their
room treatments. The Auralexian features rooms submitted to Auralex via the
Personalized Room Analysis Form.
:: July 2004
Who: Keys Curry
What: Project Studio, Writing Room
Where: Houston, TX
Why: Minimize sound transmission and provide
accurate mixing and recording environment.
:: May 2004
Who: Alan and Dawn Drake
What: Cedar Rock Studio
Where: Shelburn, IN
Why: Interior Sound Quality treatments for four large
isolation rooms featuring Auralex Metro and DST
acoustical treatments.
News & Notes
:: April 2004
Who: Dr. Henry Yuen
What: Dedicated Home Theater
Where: London, England
Why: Improve sound quality (low frequency response,
flutter echo, etc.) of home theater space in order to
maximize the performance of the system and its
components. (1 of 2) [10/3/04 8:12:18 PM]
Auralex Acoustics - The Auralexian!
Auralex Newsletter
:: March 2004
Who: Larry Ginsburg
What: Mix, master, and general tracking room
Where: Allentown, Pennsylvania
Why: Acoustically tune a good sized space (18'x13')
with some irregular features to yield an accurate
Project Studio.
:: February 2004
Who: Kevin Donaker-Ring
What: Tracking room and rehearsal space for his
band ''The Shambles''
Where: San Diego, California
Why: Because bands make noise that neighbors don't
always appreciate.
Your Email
Your Name
We value your privacy!
:: January 2004
Who: Southport United Methodist Church
What: Church Sanctuary
Where: Indianapolis, Indiana
Why: Improve speech intelligibility and music quality
while simultaneously reducing the ambient noise level
created by the praise band during church services.
:: December 2003
Who: Charlie Fink- Heavens Door (studio)
What: Project Studio/independent label
Where: Franklin, TN
Why: Isolate transmission from neighbors and family,
and create an accurate mix and full recording
environment in an all-in-one room.
© Copyright 2004 Auralex Acoustics, Inc. (2 of 2) [10/3/04 8:12:18 PM]
Auralex Acoustics - Featured Music Industry Profiles!
Auralex Acoustics - Featured Music Industry Profiles!
Site Search
Featured Products
:: Blue Microphones - Skipper Wise
Skipper Wise is a consummate musician and
cornerstone of the recording industry. His career
includes successes as both a recording artist and
manufacturer, BLUE Microphones.
:: Craig Fuller 2: A Video Tour
Craig Fuller personally takes us on a video tour of his
cozy, yet effective, home project studio. Craig's studio
is decked out in Auralex and this video gives a good
idea of how it is all laid out!
:: Craig Fuller
News & Notes (1 of 5) [10/3/04 8:12:48 PM]
Singer/songwriter/guitarist Craig Fuller was a founding
member of the folk-rock group Pure Prairie League in
1970. Fuller was with the group for its first two
albums, leaving in 1972. In 1976, Fuller joined
American Flyer, which made two albums, after which
Fuller teamed up with singer/songwriter Eric Kaz, also
a member of American Flyer, for a 1978 duo album. In
1988, Fuller joined a reunited edition of Little Feat.
Auralex Acoustics - Featured Music Industry Profiles!
Auralex Newsletter
:: Johnny A.
Creating your own unique ‘voice’ and carving out a
name for yourself is an almost impossible task for a
guitarist these days, but Favored Nations’ recording
artist Johnny A. has managed to do both.
:: Mike Fuller - Fulltone Musical Products Inc.
Your Email
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Fulltone was founded in 1991 by Michael Fuller a
Session Guitarist, Composer, Performer, and
Electronic Tinkerer. Fulltone pedals were born out of a
love for Jimi Hendrix, fine vintage pedals and Mike's
frustration at the inconsistencies and the often fragile
nature of old gear.
We value your privacy!
:: Mark "Coop DeVille" Cooper
As an award winning guitarist, author, instructor, and
international "man of mystery", Coop has played with
many of his idols and some of the music industry's
elite musicians.
:: Mark Williams
"Mixer" Mark Williams has a GRAMMY nomination,
platimum engineering credits, and is truly revered by
his peers as one of the premier recording and mix
engineers. His career has no style limits, ranging from
gospel superstar Kirk Franklin to the live recording of
the highly successful Bonnaroo Music Festival. (2 of 5) [10/3/04 8:12:48 PM]
Auralex Acoustics - Featured Music Industry Profiles!
:: Serj Tankian
Serj Tankian, the compelling singer of SOAD, in a
manner as individualistic and distinctive as his music,
embarked on a personal project studio build effort. His
web search led to Auralex's "trusty"
:: Branford Marsalis
Known for his innovative spirit and broad musical
scope, world-renown saxophonist Branford Marsalis is
equally at home on the stages of the world’s greatest
jazz clubs and classical halls. His recording career as a
leader encompasses twelve jazz albums, two classical
albums, and two Buckshot LeFonque pop releases for
Sony Music. His final recording for Columbia Records,
Contemporary Jazz, which has been hailed as his
greatest work to date, garnered the saxophonist’s
third Grammy Award.
:: Rock & Roll Hall of Fame & Museum - [PDF]
Auralex Acoustics, Inc. recently provided acoustical
treatment services and products for multiple rooms at
the Rock aNd Roll Hall of Fame & Museum in
Cleveland, OH.
The treatments were installed in the dual theaters of
the Mystery Train exhibit, the MTV Video Tree Room
and the Alan Freed Radio Studio. These rooms were all
treated with Auralex’s ELiTE Stretched Fabric System.
:: Pat Thrall
If brochures were sent to all musicians and recording
engineers embarking on professional careers, Pat
Thrall would certainly be on the cover. (3 of 5) [10/3/04 8:12:48 PM]
Auralex Acoustics - Featured Music Industry Profiles!
:: Jeff Marino
As a professional drummer, Jeff needed a place to
“hit” whenever the need arose. His objective was to
convert an 11’ X 15’ corner of his home basement
crawl space slightly over 7’ in height into one where
he could practice with a full kit, day or night, and
neither disturb his neighbors nor his family. The
completed room satisfied these objectives.
:: Don Dixon
Don Dixon is one of the music industry's greatest
unsung heroes: producer, musician, performer,
vocalist and songwriter. He is perhaps best known for
his work as producer for some of America's favorite
artists including R.E.M., Marshall Crenshaw, The
Smithereens, and his wife, Marti Jones.
:: Klipsch, Indianapolis - [PDF]
Auralex Acoustics, Inc. recently provided acoustical
consulting services and acoustical treatment products
for the new Home Theater Demo Room at the
expanded Klipsch headquarters in Indianapolis, IN.
:: Lee Roy Parnell
Lee Roy Parnell is among the elite few who can be
identified as a triple threat: an ace guitarist as well as
a distinctive singer and songwriter.
:: Todd Sucherman
Todd is the current drummer for the rock band Styx
and has worked on albums with Brian Wilson, Brian
Culbertson, Steve Cole and the Falling Wallenda's. (4 of 5) [10/3/04 8:12:48 PM]
Auralex Acoustics - Featured Music Industry Profiles!
:: GBT Studios, Nashville - [PDF]
Auralex Acoustics, Inc. recently provided acoustical
consulting services and acoustical treatment products
for the new GBT Studios facility near Nashville,
:: Henry Lee Summer - [PDF]
Henry Lee Summer is a pop music icon from the '80's.
He released four albums on EPIC/CBS Records and
scored big with two top twenty hits; Wish I Had a Girl
and Hey Baby.
:: Bothering Your Neighbors?
You should find "BOTHERING YOUR NEIGHBORS" not
only very informative but entertaining. You may never
look at your walls the same way again.
:: Studio 880
Studio 880 is a world-class recording facility featuring
a SSL studio and a vintage Neve room, private
lounges, game room, and a friendly atmosphere right
in the heart of the bay area.
:: Scott Jones Private Theater - [PDF]
Auralex Acoustics, Inc. was hired to provide acoustical
consulting services and acoustical treatment products
for the Scott Jones Private Theater in Carmel, Indiana.
© Copyright 2004 Auralex Acoustics, Inc. (5 of 5) [10/3/04 8:12:48 PM]
Auralex Acoustics - Featured Music Industry Profiles!
Music Industry Profiles
Site Search
Featured Products
Famous Auralex Users - PDF
Industry Profiles Archive
Blue Microphones - Skipper Wise
Skipper Wise is a consummate
musician and cornerstone of the
recording industry. His career includes
successes as both a recording artist
and manufacturer, BLUE Microphones.
Recently Auralex Acoustics partnered
with Blue Microphones along with TC
Electronics and DigiDesigns in a new
studio/demonstration room in Los
Angelos. The images show parts of
this exciting effort. After your
curiosity is peaked by the interview
below, please feel free to go to for more great
details and inspiration.
Auralex: Limiting to just three highlights for the sake of brevity, how would you
summarize your career to date?
News & Notes
SW: a) One of persistence and good fortune. I was able to have a career as a
recording artist/musicians for most of my life. This seemed
like an impossible goal as a kid growing up. The fact that I was able to achieve
this gave me the confidence and understanding about following my instincts.
b) The birth of my three children and for unknown reasons my wife staying with
me all these years. This has helped me to understand what family means in
everyday life. This extends to all that I do in the creative process. I am not alone
in any of the success I have had. There are many people behind the scenes that
are part of this.
c) Blue Microphones. From all the years of making records I had a list of things
that gave me problems in the recording process. Microphones were one of them.
All the Blue mics were designed from a practical point of view. They were created
as tools for myself and the people around our circle of musicians and engineers. I
was taught as a recording artist to try to find our own sound. As we each have our (1 of 3) [10/3/04 9:01:09 PM]
Auralex Acoustics - Featured Music Industry Profiles!
Auralex Newsletter
own personalities, I was taught to put as much of myself as I could muster into
my work. I feel the my partner Martins and I have achieved this at Blue in the
sense of our look and sound, based on quality craftsmanship and unique designs.
Our personalities, as strange as they may be are well represented.
Auralex: Microphones and acoustics are certainly ''tied at the hip''. What role
does acoustics have in your product development process?
SW: Without a proper acoustically built environment to record and listen in we
could not have achieved our goals in microphone design. If the room is treated
right, such as our new studio is with all the Auralex products, you can tell what is
going on with the signal you are recording. The mic plays more of a reproductive
tool and can tell you what is going on.
Auralex: Could you discuss your new facility in terms of your goals for the space?
Your Email
Your Name
SW:Within the Blue offices is 2000-foot recording studio that has just been
treated with all the Auralex products. It consists of a live room and a studio where
the recording equipment is housed. The studio area has been treated with Auralex
Pro Panels and is best describes as ABSOLUTLEY GEORGEOUS. It’s like being in a
private home theater. The live room has been Auralex treated in a manner to keep
the liveliness present and compliment the instruments tonal character.
We value your privacy!
The working concept is based around some of the most respected manufactures in
pro audio that have banded together to create an environment to teach personal
how their equipment functions in the real world. We at Blue Microphones are
proud to have, Digidesign, TC Electronics, Auralex and Focusrite as partners in this
endeavor. Yamaha has donated some musical instruments and Argosy console has
provided us with the console frame and rack enclosure to house the respected
outboard processing equipment.
Throughout the year various manufacturers will sponsor trainings using each
other’s equipment to show how to help the consumers integrate, and benefit from
each other’s products. It is a first of it’s kind and we are proud to be part of this
new exciting facility.
Auralex: Where do you see BLUE Microphones heading in the next ten years?
SW: Hopefully creating something relevant. I say this with a serious tone as I had
spent 25 years making records but have been out of it for about 4 years now.
Most likely I will need to find my way in the music side of things again in the near
future, as what we have designed and manufactured is based on my and partner
Martins Saulespurens own experiences. Without that process of being in the socalled trenches you can be come out of touch. Things are changing rapidly. The
recording process is quite different
today from what it once used to be
many years ago. Microphones need to
change as well to compliment this
ever-evolving times. This is our
underlying theme to the future.
Fortunately for us, microphones will
be needed in the recording process
for a while unless someone develops
a USB connector to plug into your
Auralex: Flyer question- taking
anything musically related off the list
of options, how would you most like to spend tomorrow?
SW: Being alive and looking forward! (2 of 3) [10/3/04 9:01:09 PM]
Auralex Acoustics - Featured Music Industry Profiles!
Thank you Skipper for your great support of Auralex and for your offerings to the
music we all enjoy.
© Copyright 2004 Auralex Acoustics, Inc. (3 of 3) [10/3/04 9:01:09 PM]
Auralex Acoustics - Featured Music Industry Profiles!
Music Industry Profiles
Site Search
Famous Auralex Users - PDF
Featured Products
Industry Profiles Archive
Mark Williams
''Mixer'' Mark Williams has a GRAMMY nomination,
platinum engineering credits, and is truly revered by his
peers as one of the premier recording and mix
engineers. His career has no style limits, ranging from
gospel superstar Kirk Franklin to the live recording of
the highly successful Bonnaroo Music Festival.
Recently, Auralex Acoustics' Product Specialist, Jeff
Hedback, sought Mark's perspective, via an e-mail
interview, on the effects of control room acoustics, his
mix approach, and his unfailing drive to make great
JH: ''Briefly, describe how you started recording music.''
MW: ''Up through High School, I was determined to pursue a career as an artist
(painter, not performer) like my parents. Discouraged by a lack of good art classes
during my one year in college, I began to work in underground radio and also look
at booking artists as a line of work. This was in Chicago at the end of the 1960's
and demo recordings were not as commonly used at that time for booking. Playing
recordings of my folk artists to club owners seemed like a good way to get
bookings, so I assembled a pile of old gear to make live recordings of my acts.
Very soon I was being hired by artists that I was not booking to make recordings
for them, and I got out of the booking altogether to became a recording guy.''
News & Notes
JH: ''How has your knowledge and awareness of control room acoustics effected
your work over the years?''
MW: ''Early on I realized that one of the great challenges for an engineer was to
make mixes translate from the control room to the consumer's listening
environment. To this end I originally concentrated on checking mixes by listening
to various dinky speakers, car radios, and even using small FM transmitters to
send mixes out to a car in the parking lot. Acoustics for control rooms used to be
just sort of dead with occasional mysterious bass traps. And graphic EQ was a
badly abused Band-Aid in many studios; often causing as many problems as it was
hoped to cure. Mastering labs generally had better control room acoustics and as I
began to attend more mastering sessions I began to realize that resonant (1 of 2) [10/3/04 9:02:14 PM]
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problems in a studio control room were often the biggest set of problems. Having
mid band resonance in a control room could make me think my mixes had a
richness and color that unfortunately only existed in that particular space, not in
the mix. Nowadays, a better understanding of acoustic resonance and the
availability of devices to treat it make it possible to hear much more accurately
while mixing.''
JH: ''Do you have any reference methods to see if problematic reflections or
modal issues are likely to alter your mix decisions?''
MW: ''I carry several CDs of familiar material and I make sounds with my voice
and hands to listen for anomalies that may be present, such as flutter echoes and
resonances. I also have a MAX-Wall system that I have added into rooms where I
felt some immediate improvement was needed.''
JH: ''What begins the mix process for you? In other words, do you start with the
entire track and refine, or do you start from one source and build?''
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MW: ''To become familiar with a track that I am mixing (if it is not something I've
recorded myself), I study rough mixes from the tracking sessions and may listen
to many of the tracks at once. Following that, I clear the faders and begin
balancing what I call the ''rhythm engine'', as in bass, drums, and chords. As this
foundation begins to function, I next add the lead vocal and begin to wrap the
other instruments and voices around it. Once the mix has been essentially
assembled, I try to avoid soloing individual tracks more than absolutely
necessarily. This is because what really matters is how those sounds relate to the
others and make it through the mix rather than how they sound individually. If
you make too many decisions while soloed, your sounds and internal blends will
not take masking effects adequately into consideration.''
JH: ''Mark, I'm aware that you have an Auralex treated editing suite. Can you
describe how this room functions as a part of your business (so to speak)?''
MW: ''My projects take me to many different studios, mobile trucks, and locations.
All of these projects bounce from one format to another and my edit suite is a
space that allows me to handle many interim parts of projects, including edits,
auto-tuning, transfers, comp'ing, etc. So much of modern production involves
fiddling with computers and this gives me a space where I can hear well and take
care of these chores without needing to rent another facility.''
JH: ''There have been many changes in the recording and record businesses in the
last five years alone, from your perspective, what are the most important aspects
to keep in focus regarding making great music?''
MW: ''Projects that were made with a vision by artists with something to say
seem to be the projects that I still enjoy years after working on them. Attempts to
manufacture hits are often just cheap shots with no real content to sustain them
past momentary fashion. Good productions of good music should stand for years
and bring a better artistic and financial return.''
JH: Thank you Mark for this embedded ''snapshot'' into the battlefield known as
the control room. Your support of Auralex Acoustics has been and will continue to
be greatly appreciated. Happy mixing!
© Copyright 2004 Auralex Acoustics, Inc. (2 of 2) [10/3/04 9:02:14 PM]
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