United States Patent
US007162046B2
(12)
(54)
United States Patent
(10) Patent N0.:
Schwartz
(45) Date of Patent:
*Jan. 9, 2007
MICROPHONE-TAILORED EQUALIZING
4,994,770 A *
SYSTEM
5,194,681 A
3/1993
Kudo ...... ..
5,466,882 A
11/1995
Lee ......... ..
(76)
Inventor:
Stephen
St" Provldence’
~ R. Schwartz,
RI (Us)172
02906
Congdon
(*)
Notice:
This patent issued on a continued pros
.
.
5,537,614
,
,
i
A *
,
84/603
.
.
84/603
7/1996 x1118;
Hagimori
or1 aWae
et alt-"1m
et al.
a. ........
.
.. 381/58
yenkho?p """" "
,
ehoe
333/28 R
....................... ..
381/61
6,141,425 A * 10/2000 Murayama et al. ......... .. 381/98
1.53(d), and 1s subject to the tWenty year
patent term provisions of 35 U.S.C. 154
OTHER PUBLICATIONS
(20(2)
Bartlett, Bruce, “Tonal Effects of Close Microphone Placement”;
.
.
.
.
Subject
to any d1scla1mer,
the term of this
J
lfA d'
'
'
S
'
,
7323289,.
u 10 E ngmeenng
oclety
V0 l.29,N.100t.1981,
0
C
pp .
Pawnt 15 extended or adlusted under 35
K&K Sound Systems, Drum and Percussion Microphones; pp. 1-2
U.S.C. 154(1)) by 0 days-
(http://WWW.kksound.corn/drurnic.htm).
(21) Appl. NO.Z 09/072,412
.
2/1991 Niwayama ................. .. 381/98
i i
.
ecunon aPPhFaUOI? ?led under 37 CPR
(22)
US 7,162,046 B2
* Cited by examiner
_
Primary ExamineriBrian T. Pendleton
Flled'
May 4’ 1998
(65)
74 Allorney, A [email protected], 0r FirmiKeny O11 & KenyO11 LLP
Prior Publication Data
US 2001/0043704 A1
(57)
Nov. 22, 2001
ABSTRACT
_
_
_
(51)
Int_ CL
H03G 5/00
(200601)
A method and system 1s descrlbed to 1mprove the reproduc
tion of sound of an acoustic musical instrument. According
to one embodiment, a ?rst microphone is placed at a
(52)
(58)
US. Cl. ...................................................... .. 381/98
Field 61 Classi?cation Search .............. .. 381/203
proximate location to the musical instrument to Pick up the
Sound Of‘he musical instmmem- The Sound as Picked uP by
381/98 103. 84/723 736 738 730 731’
the ?rst microphone is compared to a reference sound of the
See application ?le’ for éomplete’searéh hi’storyf
instrument (e.g., the sound of the instrument as perceived at
a normal listening position). Based on this comparison, a
(56)
References Cited
tailor-made equalizer is designed to compensate for the
US. PATENT DOCUMENTS
diiferences between the sounds as picked up by the ?rst
microphone and the reference sounds of the musical instru
4,118,601 A * 10/1978 Yeap
ment. Accordingly, using the tailor-made equalizer alloWs
4,306,113 A *
the reproduction of sound from the ?rst microphone to have
12/1981 Morton
4,311,872 A *
1/1982
4,316,060 A *
2/1982 Adams et al. ..
4,340,780 A
7/1982
4,389,915 A
4,696,214 A
4,882,963 A
*
Davis ....................... .. 330/294
Odlen
....... ..
6/1983 Bione
9/1987 Ichiki
11/1989
Ichiki .............. ..
4,947,723 A
8/1990 Kawashima et al.
4,991,218 A
2/1991
/
381/98
.. 381/103
84/1.24
84/101
84/101
a quality similar to that of the reference sound of the musical
instrument. In an implementation of the above system, a
?lter arrangement is provided having a loW-pass and a
high-pass ?lter that alloWs separate control of the frequency
and/or gain for each ?lter.
18 Claims, 4 Drawing Sheets
Kramer ..................... .. 381/61
12
Microphone
Instrument —' (“V-Option?‘I
?tiachmem
device)
Microphone
..__>l Ampli?er (w.
optional mic
power supply)
/ l3
Specialized
-—>( Processor
/- l4
Recording
' device, PA
system,etc.
U.S. Patent
Jan. 9, 2007
US 7,162,046 B2
Sheet 3 0f 4
Figure 3
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U.S. Patent
Jan. 9, 2007
Sheet 4 0f 4
Fig. 6
Fig. 7
Fig. 8
US 7,162,046 B2
US 7,162,046 B2
1
2
MICROPHONE-TAILORED EQUALIZING
speakers or other musical instruments, feedback and isola
tion problems are greatly reduced. Also, because they are
attached to and move With the instrument, the problems of
SYSTEM
changing volume and tone quality caused by a performer’s
BACKGROUND OF THE INVENTION
movement are eliminated.
1. Field of the Invention
The draWback to using contact or induction pickups,
The invention relates to microphone pickup and electronic
hoWever, is that the result is extremely loW ?delity. The
ampli?cation of musical instruments, particularly acoustic
vibrations of a string or sounding board of a violin, for
example, are drastically different from the vibrations of the
air around the instrument. But What is de?ned as the
“acoustic sound” of the instrument is What the ear hears as
the vibration produced in the air in response to the sum of
vibrations of all the instrument’s parts, as described above.
Thus, these transducers have been very effective in devel
oping neW electric instruments With their oWn sound (espe
musical instruments, for concerts or recordings.
2. Background Art
Pickups for electronically reproducing sound from musi
cal instruments are of tWo general types, pressure and
vibration. Apressure pickup or microphone has a diaphragm
that vibrates in response to acoustic pressure variations in
air. The diaphragm vibrations are transformed into an elec
trical signal. Since the human ear also has a diaphragm that
Works in the same Way, the acoustic response of a good
pressure type microphone located at an optimal distance
from a musical instrument approximates the sound of the
instrument in a given room. Pressure-type microphones
cially electric guitar and electric bass). HoWever, their
abilities are limited for the high ?delity reproduction of
sound from acoustic instruments.
For the above reasons, current practice for electronically
20
present problems of isolation, placement, and feedback,
transducing and ?ltering live music from acoustic instru
ments is to use a quality directional microphone or micro
phones set up near, and aimed at, a single instrument or
hoWever.
The isolation problem results from pickup sounds from
group of instruments. These microphones send their signal
both desired sources (the instrument or instruments that one
Wants to amplify) and undesired sources (e.g., a cough or
via a special cable to a special pre-ampli?er (Which some
times sends poWer to the mic). This then connects to general
25
purpose equalizer and mixing circuits. For example, in a
rock band a typical drum set (?ve drums, one hi-hat, and tWo
cymbals) may have one directional microphone for each
another musical instrument that one Wishes to amplify
separately). The conventional approach to minimizing the
isolation problem is to place the microphone close to the
selected instrument to be picked up and to use a so-called
directional microphone, Which attempts to reject sound from
drum and the hi-hat, mounted on a stand very close to the
30
unWanted directions.
stereo effect and to pick up the cymbals. The tWo overhead
microphones must be at least a foot or so from the cymbals
to avoid picking up a loud metallic hum. A guitar may have
Since sound radiates by the inverse square laW, moving
the microphone closer to the instrument reduces the isolation
problem by increasing the amplitude of sound from the
selected instrument relative to the sound from other sources.
35
This solution, hoWever, increases the placement problem.
one or tWo of these mics placed betWeen one and three feet
aWay.
As previously mentioned, it is also common to mount
pickup devices directly on individual instruments, typically
Musical instruments generate sound from different parts,
such as the strings, sound box, and front and back surfaces
of a violin. At a normal listening distance from a musical
instrument, the characteristic sound of the instrument is an
drum, plus tWo “overhead” directional microphones for
40
amalgam of the sounds generated from each part.
guitars, to produce a different type of sound from that
produced by the conventional “acoustic” form of the same
kind of instrument. These pickups sense the vibration of
some part of the instrument, such as the front soundboard of
a guitar. Examples of such pickups are described in Us. Pat.
Different spots in the area close to an instrument (espe
cially Within a foot or so) yield very different sounds, most
become so exaggerated that one spot sounds very different
from another, and it can be dif?cult to tell What instrument
No. 4,051,761 of Nylen, U.S. Pat. No. 4,143,575 of Oliver,
U.S. Pat. No. 4,423,654 ofYamagami, U.S. Pat. No. 4,481,
854 of Dugas, U.S. Pat. No. 4,837,836 of Barcus, U.S. Pat.
No. 5,136,918 of Ribololf, and Us. Pat. No. 5,206,449 of
McClish. The ampli?ed sound from these vibration sensitive
is being listened to. Also, if the instrument is not stationary,
pickups mounted on either acoustic or so-called electric or
or all of Which a listener Would consider unnatural. When
extremely close (less than a feW inches), the differences
45
electronic instruments differs intentionally from the sound
but is held by the musician (guitar, violin, ?ute, etc.), small
normal movements of the performer produce unintended and
undesired changes in dynamic level (volume) and tone
50
quality.
Feedback is a special circumstance arising from isolation
and placement problems, typically during the types of live
performance Where performers hear themselves by listening
55
to monitor speakers aimed in their direction. These speakers
are thus also aimed at the microphone used to pick up the
sound initially. This can create a positive feedback loop that
vibration pickups attached to the instruments themselves
have been used. These pickups sense either the vibration of
the instrument at the spot Where they are attached (contact
pickup) or the vibration of a metallic string (magnetic
induction pickup) of a stringed instrument. As these pickups
do not respond to the sound in air produced by monitor
type microphones mounted at a distance from the instru
ment; so these vibration pickups are not suitable for high
?delity electronic reproduction of the sound of an acoustic
instrument.
It has been proposed to mount miniature pressure-sensi
tive microphones directly on musical instruments for spe
ci?c purposes. For example, U.S. Pat. No. 4,837,836 issued
to Barcus on Jun. 6, 1989 addresses the drawbacks of using
stationary conventional microphones to pick up musical
drives the speaker ampli?er into saturation, producing a loud
hoWl. The usual corrective for feedback is to use directional
microphones, but this is of limited use. As a last resort,
produced by acoustic instruments and sensed by pressure
60
instruments in general, and also of holding a standard full
siZe microphone close to, or attaching a miniature micro
phone directly to, an accordion or harmonica in particular.
These draWbacks include feedback from nearby speakers
65
and undesirable emphasis of the sounds coming from a
localiZed portion of the elongated reed banks of accordions
and harmonicas; that is, an increased volume of the notes
Whose reeds are near Where the microphone is attached.
US 7,162,046 B2
3
4
To overcome the drawbacks of the prior arrangements,
Barcus provides a pickup module in Which a miniature
the use of one or more microphones placed proximately to,
on or inside an instrument. For example, the microphone can
be mounted permanently on or in the instrument, or it can be
pressure-type microphone capsule is embedded. The module
attached temporarily to the instrument With a clip designed
for the speci?c instrument in question. It may also be held
has an elongated narroW sound guide channel extending
betWeen oppositely facing open ends, and a sound sensitive
surface area of the microphone communicates With the
central region of the channel. The narroW sound channel
creates a tWo-lobed directional sensitivity pattern for the
microphone in an attempt to respond more equally to all
notes When the module is centrally mounted on an elongated
reed bank of a harmonica or accordion. Barcus also suggests
on a stand When feasible and preferable. While any micro
phone of suitable quality Will do, a miniature microphone
(and particularly When attached to the instrument) has tWo
advantages. First, it is easier to accurately place, and Will go
10
in some places that a normal microphone Will not ?t.
Second, it Will move With a non-stationary (e. g., hand-held)
instrument, and so avoid unWanted changes of sound quality
that the module may be used With other musical instruments,
and speci?cally that it can be attached to a drumhead near
that arise When an instrument moves relative to a micro
the edge of the drumhead to avoid feedback, pickup of an
phone.
undesirable amount of room ambience, and lack of presence
that occur With a conventional microphone stationed in front
of the drum.
This lack of presence, a subjective term often used to
The system may include a suitably designed microphone
preamp connected in tandem With and closely positioned
(less than eight meters and preferably 3 to 6 meters) to at
least one microphone. The microphone preamp delivers dc
poWer to the microphone (if needed) as Well as receiving,
and initially amplifying, the audio signal from the micro
describe a characteristic frequency band (Which is different
for each sound source), has not been noticed by the present
inventor. HoWever, in trials by the inventor using a variety
of shapes, it has been noticed that strong, unnatural (and
unpleasant) sounding frequency peaks are created by the
shape of the cavity surrounding the microphone. These
shaped microphone enclosures invariably add more prob
20
phone.
Another feature of the system is an equaliZer unit that is
“tailor-made” for each type of instrument and, more par
ticularly, for a preselected optimum microphone location on
25
lems than are solved in efforts to replicate the instrument’s
acoustic sound. The Barcus patent has a chart that looks like
it may shoW improved frequency response, but it only shoWs
improved evenness of volume from note to note. Test results
of the inventor shoW each note Would have a seriously
general purpose equaliZers having four or more adjustable
?lters, With up to three controls for each ?lter (a total of
30
degraded frequency response When compared to a high
?delity reference.
?lter control can be limited to the smallest useful range that
35
In an example using a piano, the output of a detecting unit
having 1) vibration sensors attached to the bridges and
agraffes, 2) electromagnetic pickup units close to the strings,
and 3) microphones attached to the sound board is delivered
to a digital processing unit. Processors actuated by the
various types of sensors for controlling loudness, delay,
equalization, and phase difference deliver their output to
40
alloWs enough ?exibility for variations betWeen individual
instruments.
Each equaliZer can be combined With a preampli?er in a
small, lightWeight package that can be mounted close to the
performer. This alloWs the individual musicians to achieve
their oWn preferred “sound” Without needing a skilled audio
technician to make complex multiple adjustments at a mas
ter equaliZer console.
These features of the system sharply reduce the cost of the
vibration actuators mounted on the sound board and case
boards of the piano. A parameter determining means adjusts
the various processors so that the actuators create additional
tWelve or more knobs), these units may have only a mini
mum number and type of ?lters needed to compensate for
the differences betWeen the instrument’s sound at a normal
listening spot and the microphone attachment spot. Each
U.S. Pat. No. 5,262,586, issued to Oba et al. on Nov. 16,
1993, discloses a sound controller for an acoustic musical
instrument to modify the sound produced by the instrument.
each type of instrument. The equaliZer may include conven
tional loW pass, high pass, band pass, and/or notch ?lters, or
other processors, as appropriate. Contrary to conventional
audio input equipment for a band or orchestra and dramati
45
cally shorten the time required to set up the equipment for
vibrations to produce acoustic sounds With modi?ed quali
a concert or recording session. They also enable a musician
ties. Thus, Oba et al. use microphones as one of several types
of pickups mounted inside a musical instrument to feed
only by a sound engineer.
or other person to accomplish What is presently achievable
sounds and vibrations generated by playing the instrument to
a vibration unit that alters the acoustic output of the instru
ment. Oba et al. do not use these microphones to produce an
electronic signal in response to the acoustic output of the
instrument for recording or amplifying the unmodi?ed out
put. Consequently, none of the arrangements of the prior art
provides a high ?delity solution to the problems of micro
phone isolation and placement encountered in electronic
reproduction of sound from an acoustic musical instrument.
Each case is currently successful only via careful tailoring
50
desired to be duplicated in quality by the attached micro
phone and tailor-made equaliZer. In its simplest form, it
means the sound of an instrument being played and listened
55
to in its normal environment (but generally exclusive of the
room’s in?uence on the sound). For example, if a guitar
player plays a guitar in a pleasant and dry (non-reverberant)
60
sounding room, the “reference sounds of the instrument”
Would be the acoustic signature of the sound at a good/
normal listening position in that room. A second reference
method is When a high quality reference microphone is used
to capture this sound, and a third reference method is When
the microphone signal is recorded on a hi quality storage
device (such as a digital tape recorder).
65
preferably is spaced from the instrument a su?icient distance
by a sound engineer using sophisticated equipment.
SUMMARY OF THE INVENTION
The present invention provides a method for designing a
system (microphones, attachment mechanisms, and associ
ated preampli?ers, equaliZers, and processors) to be used
As used herein, the term “reference sounds of the instru
ment” means sounds produced by the instrument that are
When using a microphone reference, the listening site
With solo or group musical instruments, and the system as
to permit the reference microphone to pick up the optimum
designed by the method. A principal feature of the system is
sound quality of the instrument (generally, a distance from
US 7,162,046 B2
5
6
the instrument equal to the Width of instrument). This spot
The fourth step of making simultaneous ?rst and second
audio recordings preferably can include making multi-track
recordings on a digital or other high quality recording
medium.
The ?fth step of comparing the ?rst and second audio
recordings preferably includes displaying acoustic Wave
forms of the ?rst and second recordings; equalizing one of
the ?rst and second Waveforms to substantially conform to
the other Waveform; and using the equalization values to
design the tailor-made equalizer for the ?rst microphone in
also should avoid the sound of the room. The room itself
should be made to contribute minimally to the sound
received at the microphone(s). A common terminology for
this is to say the mic is placed in a mid-?eld position, and
the room is dry or damped (literally:"discouraged”). An
anechoic chamber is an ideal room, as it Would make certain
aspects of the design process easier and perhaps more
accurate. However, these rooms are rare and very expensive,
and not necessary to the method.
step (6).
Speci?cally, the present invention provides a method for
The present invention also provides a system for high
?delity electronic reproduction of the sound of an acoustic
designing a system for high ?delity reproduction of the
sound of a selected type of acoustic musical instrument, and
also for providing embodiments of the system, the method
musical instrument, the system comprising:
comprising:
a microphone element or elements;
(1) placing a ?rst microphone proximately to the acoustic
musical instrument;
(2) playing the musical instrument to produce sounds as
picked up by the ?rst microphone and playing reference
sounds of the instrument;
(3) comparing the sounds of the musical instrument as
picked up by the ?rst microphone With the reference sounds
of the instrument; and
(4) designing a tailor-made equalizer to compensate for
microphone attachment devices, Where suitable or advan
the differences betWeen the sounds as picked up by the
microphone and the reference sounds of the instrument.
The method of the present invention may additionally
include:
selecting an attachment location in step 1 by locating the
tageous;
20
25
preselected location on the particular instrument so as to
30
35
comparing sounds as picked up by the ?rst microphone at
each attachment location With the reference sounds of
the instrument, and
selecting the attachment location at Which the ampli?ed
microphone sound is closest to the reference sound of
the instrument.
preferred embodiment of the method comprises:
(1) placing a ?rst microphone proximately to the acoustic
musical instrument;
(2) positioning a high quality reference second micro
phone at an appropriate listening site (normally mid-?eld, as
discussed above) for the acoustic musical instrument;
(3) playing the musical instrument to produce reference
and one loW-pass ?lter, With a total of ?ve controls. Hi-hat
40
With the detailed description of the preferred embodiments.
45
BRIEF DESCRIPTION OF THE DRAWINGS
50
second microphone;
55
according to an embodiment of the invention for a bass
FIG. 4 is a block diagram of an equalizer circuit designed
according to an embodiment of the invention for a snare
60
drum;
FIG. 5 is a block diagram of an equalizer circuit designed
according to an embodiment of the invention for a tom-tom.
recording from the second sound recording.
FIG. 6 is a graphic diagram shoWing hoW a loW-pass and
a high pass ?lter are combined in series as knoWn in the art.
The method of the invention may further include repeat
ing the above steps (1) through (5) using different musical
FIG. 1 is a general block diagram of an equalizer system
designed according to an embodiment of the present inven
tion.
FIG. 2A is a general block diagram of an equalizer for a
miniature microphone attached to an acoustic guitar;
FIG. 2B is a schematic diagram of the circuit of FIG. 2A;
FIG. 3 is a block diagram of an equalizer circuit designed
drum;
the respective ?rst and second microphones;
(5) comparing the ?rst and second audio recordings to
determine the audio differences betWeen the recordings; and
(6) designing a tailor-made equalizer for the ?rst micro
phone to compensate for the differences of the ?rst sound
and cymbal equalizers have only a high-pass ?lter in series
With a single notch ?lter, but With three controls.
The above-described and other features and advantages of
the invention are presented in the draWings in connection
sounds of the instrument as picked up by the reference
(4) making simultaneous ?rst and second audio record
ings of the sounds of the musical instrument as picked up by
avoid or minimize altering the sounds produced by the
instrument and to enable a performer to play the instrument
unencumbered.
The equalizer may comprise one or more electronic ?lter
types, depending on the type of musical instrument. For
example, a tailor-made equalizer for acoustic guitars has a
high-pass ?lter and tWo notch (band-reject) ?lters. A tom
tom drum equalizer has one high-pass ?lter and one loW
pass ?lter. A bass drum equalizer has three high-pass ?lters
Although the step of comparing the sounds picked up by
the ?rst microphone With reference sounds of the instrument
can be made by listening directly to the tWo sounds, a
cal instrument.
The mounting device may also include a device for
removably attaching the microphone to the instrument, the
device being speci?cally designed for attachment at the
?rst microphone successively at a plurality of possible
attachment locations that do not interfere With playing
the instrument,
playing the instrument to produce reference sounds of the
instrument,
an equalizer having an input coupled to the microphone,
the equalizer including a predetermined minimum number
of electronic ?lter circuits, controls, and control ranges
optimized to compensate for differences in the electronic
reproduction by the microphone element, of sounds from the
preselected type of acoustic musical instrument compared
With corresponding reference sounds from the type of musi
65
FIG. 7 is a graphic diagram shoWing hoW a loW-pass and
instruments of the same type to determine adjustment ranges
a high-pass ?lter are combined in parallel according to an
for sections of the equalizer designed in step (6).
embodiment of the present invention.
US 7,162,046 B2
7
8
FIG. 8 is graphic diagram of a second embodiment of the
present invention combining a loW-pass ?lter and a high
pass ?lter in parallel.
effect of room sound on the sound of an acoustic instrument
Without the expense of an anechoic chamber, it has become
the norm in both the sound-reinforcement and recording and
broadcast industries to use unidirectional microphones
DETAILED DESCRIPTION
placed in What is called the mid ?eld. The microphone is
placed far enough aWay to get the natural sound of the entire
According to the present invention, the microphone
instrument, but as close as possible to avoid the sound of the
assembly includes a microphone such as an omnidirectional
or unidirectional microphone element, such as a Model No.
room. This distance is generally about the same as the
average dimension of the instrument or a group of instru
DPA 4060 microphone manufactured by Bruel and Kjaer.
ments.
The microphone element can be attached to a clip or housing
Because unidirectional microphones reject only a portion
to permit for temporarily attaching the microphone assembly
of sound coming from unWanted directions, and because
to a pre-selected spot on or in an acoustic musical instru
some unWanted sound comes from behind the instrument, a
ment. Other temporary attachment arrangements may be
provided When necessary. The clips or other attachment
signi?cant amount of room and other sound may be still
picked up at a mid ?eld listening position. To eliminate this,
a microphone is placed in the near ?eld, spaced about zero
devices are selected to minimize mass loading of the instru
ment structure to Which the microphone is attached. In some
to tWelve inches aWay from the instrument. This is knoWn as
cases, permanent attachment of the microphone assembly to
“close micing.” This strongly increases the ratio of instru
a speci?c musical instrument by suitable means may be
ment sound to room and other sound, because of the inverse
square relation of distance from source to energy of sound.
Close micing produces a less natural sound than listeners are
used to, hoWever; even the ears of the musician playing the
instrument are further aWay than the close mic in most cases.
acceptable. Alternatively, the microphone can be placed
20
proximately to the musical instrument rather than being
attached to the musical instrument.
Referring to FIG. 1, a general block diagram of an
equalizer system is shoWn constructed according to an
embodiment of the present invention. Block 10 represents an
Various processing equipment is usually needed to improve
25
instrument such as the instruments described beloW. Sounds
generated by instrument 10 are picked up by a microphone
11 (e.g., attached to the instrument). The sounds picked up
by microphone 11 are provided to a microphone poWer
supply (if needed) and ampli?er 12 and a specialized pro
noted that for some instruments, hoWever, particularly
drumset components and certain vocal styles, a “close mic”
sound has become the musical norm because the most
30
common listening experience of these instruments has been
a close-miced recording or performance. If close micing
becomes more Widely used, other instruments may have
their ‘sound’ de?ned this Way.
35
comparable in equipment and sound characteristics to a
cessor 13 (e.g., a tailor-made equalizer as described beloW).
The output of the specialized processor 13 is then provided
to an appropriate output device 14 such as a recording
device, a public address (PA) system, a speaker system, etc.
In practicing the method of the invention for designing a
tailor-made microphone and equalizer system for a speci?c
type of acoustic musical instrument, the ?rst step is to place
a microphone proximately to the instrument. Alternatively,
For most purposes, it is desirable to have a listening room
the microphone can be attached to a location on or in an
instrument of the selected type. The placement location is
preselected With a vieW to sensing an airborne acoustic
signature that is as little different as possible from the
acoustic signature of the instrument When heard or sensed at
a normal listening site spaced from the instrument. The term
“listening site” refers either to a location for a human auditor
or to a location for placement of a reference microphone to
40
Microphone preampli?er (Mic Preamp 2)iSymetrix
What constitutes a normal listening site includes hoW
Parametric equalizer (EQ 1)4Orban Model 621B (four
50
varies signi?cantly from place to place in a given room.
Acoustic engineers designate a location Where the sound of
55
Monitor ampli?er (Amp)iMacintosh Model 6200;
Small near ?eld monitor speaker (Spkr 1)iRogers Model
LS3/5A, BBC near ?eld reference standard;
Large monitor speaker (Spkr 2)iTannoy Dual-Concen
tric 12-inch, tuned to room With UREI Model 539 Room
60
Equalizer;
Mixer (Mxr)iHill Model B3 24><8><2 (uses 5532 opera
tional ampli?ers);
Worse than having no room sound at all. In an anechoic
sound, regardless of listening location. To eliminate the
Parametric equalizer (EQ 2)iSymetrix Model SX201
(three bands per channel);
Graphic equalizer (EQ 3)iDOD Model R-231 (one-third
required. Most often, hoWever, room effect is undesirable,
since a poorly selected listening site can produce results
chamber, or even a heavily draped and carpeted room,
reverberation is essentially eliminated and there is no room
bands per channel);
octave per band, 31 bands per channel);
ing environment such as Carnegie Hall, using microphones
in the far ?eld to involve the sound of the room can produce
excellent results, so long as no sound reinforcement is
Model M1;
Model 201;
much, if any, “room sound” (i.e. reverberation) is desired.
an instrument is augmented by room sound as the “far ?eld”
and a location Where the sound of an instrument is substan
tially unaffected by room sound as the “mid ?eld”or “near
?eld.”
In some recording or broadcast situations, With an instru
ment ensemble or orchestra in an exceptionally nice sound
professional recording studio. The folloWing equipment list
is given by Way of example:
Unidirectional dynamic reference microphone (RefIVIic
1)iSennheiser Model MD441 super-cardioid dynamic;
Unidirectional condenser reference microphone (RefIVIic
2)iNeumann K150 hyper-cardioid condenser;
Omnidirectional dynamic reference microphone (RefIVIic
3)iSennheiser Model MD211 dynamic;
Microphone preampli?er (Mic Preamp 1)iJohn Hardy
45
pick up sound for ampli?cation.
The sound of an instrument differs in each room, and even
the nature of close-miced sound. The present invention
improves and optimizes this, as shoWn beloW. It should be
65
Multi-channel audio tape recorderiAlesis Digital Audio
Tape (ADAT) multi-channel recorder, run at 48 kHz;
Real Time Analyzer (RTA)iAudio Control Model
SA-3050A one-third octave With calibrated microphone
(ANSI Class S1.11-1971)
US 7,162,046 B2
10
manufacturer and model in each case is not intended to be
merely by listening to the sound quality of a loudspeaker
With music or voice signals being the input. This is actually
exclusive. Other makes and models of comparable or better
a leamable art and discipline.”
The above list is not exhaustive, and the choice of
quality may be used.
(Pg. 1408) D. & C. Davis: “Walking the audience areas
The choice of a reference microphone depends on the
While using the most sophisticated analyZer available,
choice of listening site. Repeated comparisons betWeen a
namely the trained ear-brain system, determine the best
condenser microphone (RefMic 2) and several dynamic
microphones (RefMic 1) rarely shoWed signi?cant differ
areas and the Worst areas. Then measure With equipment in
the best areas for reference use and the Worst areas for
ences, hoWever, and it is usually suf?cient to use a RefMic
1.
correction purposes.
As stated in the summary of the invention, the term,
“reference sounds of the instrument,” means sounds pro
duced by the instrument that are desired to be duplicated in
relative to a given situation is more revealing than any
resume of his experience.”
quality by the attached microphone and tailor-made equal
sound signal delivered by the ?rst microphone to either a
iZer. The quality or nature of sounds produced by the
instrument Will be different, hoWever, for different rooms
and for different placements of instrument and listener in a
monitor loudspeaker or an earphone can be compared
directly and simultaneously With the sound received acous
given room. Thus, the “reference” sounds used as a standard
at the listening site. During repeated playings of a speci?c
note or chord, the engineer adjusts the equaliZer to bring the
sound from the ?rst microphone into coincidence With the
reference sound heard directly.
An advantage of this Way of comparing the sounds is that
of comparison necessarily Will involve subjective choice
(this is true for all musical reproduction), but this subjec
tiveness is minimiZed by using a high quality (usually
directional) microphone at a proper (usually mid-?eld) dis
Watching an engineer place a measuring microphone
In the simplest performance of the comparison step, the
tically by an audio engineer stationed at an equaliZer located
20
the reference sound is the true acoustic sound transmitted
tance from the instrument in a room With minimal rever
from the instrument to the listening site, unaffected by
beration or other sound components. An anechoic chamber
(rarely available) Would be an ideal place for this purpose.
The step of playing the musical instrument to produce
sounds as picked up by the ?rst microphone and also
reference sounds requires a skilled musician to play, With
consistent volume and tone quality, a series of notes, chords,
and musical phrases, as appropriate, to produce musical
sounds representative of the full range of the instrument. As
the musician plays, each note and chord is picked up by the
?rst microphone, Which may be coupled through a suitable
preampli?er (e.g., Mic Preamp 1 or Mic Preamp 2), a
25
conventional professional quality equalizer (e.g., EQ 1, EQ
35
presents several disadvantages, hoWever. These include:
If tWo sounds are played together, they produce a single
combined sound, and thus color each other, so it is nearly
impossible to compare and equaliZe tWo simultaneous
30
As indicated above, the reference sound may be the acoustic
sound of the instrument heard at the listening site or may be
picked up by a reference microphone at the listening site that
approximates an average “ideal” acoustic sound. (For com
40
45
and equalizing equipment similar to that used With the ?rst
50
possible, to the direct unampli?ed sound of the musical
instrument, or When different, is close to a reference sound
desired in common practice. The equaliZer for the ?rst
microphone may next be adjusted, through successive play
60
clear:
(Pg. 253) F. Miller: “The very best piece of test equipment
sound equipment are actually capable of making judgements
and Will Work Within the ?nal design parameters. The output
of the reference microphone may be passed through a
conventional studio-quality mixer or equaliZer bank that is
adjusted to create a compensated reference sound that, When
fed to an ampli?er and monitor speaker or headphones,
produces an audio output that is identical, or as close as
55
in the audio engineering art that a skilled engineer or audio
technician can discriminate betWeen the acoustic signatures
of similar sounds at least as Well as any currently available
you oWn is your set of ears and good judgement.”
(Pg. 501) C. Hendrickson: “Some users or evaluators of
phone placed at the listening site. To obtain a complete
record, the instrument should be played through a succes
sion of notes and chords covering its full range, along With
representative musical excerpts. This entire process is
repeated With several instruments of the same type to be sure
that differences in individual instruments are accounted for
equivalent in training, making the comparison betWeen the
audio test equipment. The folloWing excerpts from articles
in “Handbook for Sound EngineersiThe NeW Audio
Cyclopedia,” 2nd edition, Glen Ballou, ed. (1991, H. W.
Sams and Co., Div. Of Macmillan, Carmel Ind.) make this
become the musically accepted standard of sound.
The preferred Way of comparing the tWo sounds, there
fore, is to simultaneously pick up and record the acoustic
sound of the instrument With a second, reference micro
microphone.)
tWo sounds and adjusting ?lters, equaliZers, etc. to bring one
sound into conformance With the other. It is Well recogniZed
forth.
It may be desirable, for some applications, to provide a
reference sound that differs from the pure acoustic signal
delivered from the instrument to the listening site. The sound
common examples Where the placement of a microphone
combined With the process of electronic modi?cation has
parison purposes, it may be processed through amplifying
The step of comparing the sounds of the musical instru
ment as picked up by the ?rst microphone With the reference
sounds of the instrument may be performed in several Ways.
Each Way preferably entails a skilled audio engineer, or
sounds. They must be listened to one at a time, Which is
someWhat less accurate than a direct comparison back-and
of a drumset and the sound of certain vocal styles are
2, or EQ 3), and an ampli?er (Amp) to a monitor loud
speaker (e.g., Spkr 1 or Spkr 2) or to headphones, as desired.
The musician produces the reference sounds either simul
taneously or alternately With the corresponding sounds
picked up by the ?rst microphone, depending on Which of
several possible Ways the comparing step is to be performed.
translation to and from electronic form. This Way also
65
ings of the instrument, to bring the sound from the ?rst
microphone into conformance With the reference sound.
The settings of the equaliZer for the ?rst microphone then
provide data for designing the tailor-made equaliZer in the
?nal step. Alternatively, after noting the initial settings of the
equaliZer for the second microphone, the technician may
adjust that equaliZer to bring the reference sound into
conformance With the sound from the ?rst microphone. The
change in settings of the second equaliZer then provides the
US 7,162,046 B2
11
12
The foregoing examples of equaliZers tailor-made for
data for designing the tailor-made equalizer of the invention.
As further described below, this adjustment can also be done
speci?c types of acoustic musical instruments demonstrate
the simple, and therefore inexpensive, solution of the present
automatically.
The use of a second, reference microphone also permits a
invention for providing high ?delity audio reproduction of
further improvement in the comparing step. Since both the
sound from the ?rst microphone and the reference sound
these instruments When combined With a microphone proxi
mately placed or directly attached to the instrument.
A further advantage of the tailored equaliZer system is a
marked increase in the rejection of unWanted sounds, func
tionally equivalent to a sharp increase in the directional
characteristics of the microphone. Also, this increase is
have been converted to electronic form, they can be simul
taneously recorded on separate tracks of a multi-channel
tape recorder (e.g., ADAT). This has tWo advantages. First,
the test data (notes, chord, and musical phrases) need be
played only once, and then can be repeated identically again
accomplished Without adding any added coloration (inaccu
and again from the tape, as adjustments are made to the
racies) to the sound. This coloration is very typical of
equalizer controls. This assures that the same sounds are
directional microphones, especially as they become
being compared each time. Secondly, the sound from the
extremely directional, because they Work by using phase
?rst microphone and the reference sound can be separated
and played back sequentially, Which makes the task of
comparing the sounds much easier. Depending Whether the
differences are relatively uniform through the high end or
loW end of the audio frequency spectrum or Whether they are
cancellations, Which are highly complex and unpredictable.
“Off-axis” response (sound from the unWanted directions) is
particularly problematic. The arrangement of tailored ?lter
in one or more relatively narroW frequency ranges, appro
elements according to an embodiment of the present inven
tion alloWs a natural sound to be produced from a spot much
20
closer to the instrument than is usually possible. Because of
priate high-pass, loW-pass, band-pass, or notch ?lter circuits
this, the inverse-square relationship betWeen distance and
can be selected and combined and the component values
determined by a competent technician to achieve the desired
energy gives a marked increase in the ratio of Wanted-to
unWanted sound, Which is What a directional microphone
attempts to do via phase cancellation. This increase happens
Without any additional phase cancellation, so the coloration
of Whatever microphone is used remains constant.
A further advantage of the method of the present inven
tion is that it alloWs the use of omni-directional microphones
in circumstances Where previously not feasible. This is
advantageous because an omni-directional microphone is
inherently smaller, more accurate, and easier to make than a
similar quality directional microphone. Even When using an
omni-directional microphone, the amount of rejection pro
vided by the method of the present invention equals or
betters that provided by even highly directional micro
phones, in many circumstances. Since omni-directional
equaliZer that is to be tailor-made for the selected type of
instrument.
FIGS. 2A and 2B shoW the results of the above-described
design process as applied to an acoustic guitar in Which the
25
miniature microphone assembly Was attached by a special
clip (not shoWn) to the sound-hole. In the equaliZer of these
?gures, an input gain circuit 60 connects to a high-pass ?lter
circuit 70 that, in turn feeds tWo band-rej ect ?lter circuits in
series 110 and 210, Which ?nally connect to an output amp
circuit 310. Since the ?lters are typical of conventional
textbook circuits, no further explanation of the their opera
tion is needed.
FIG. 3 shoWs a block diagram of a tailor-made equaliZer,
designed by the method of the invention, for a bass drum.
The output from a microphone (not shoWn) attached to a
selected location on a bass drum Would be fed through a
preampli?er (not shoWn) to a high-pass ?lter 32 having an
adjustable loWer frequency roll-o?‘ of from 16 to 160 HZ.
35
40
With an omni-directional microphone:
component of the sound from a drum of this type, Which
(having an adjustable high-frequency roll-olf ranging from
31.5 to 500 HZ). Block 36, labeled “DRY” denotes a
selectable bypass path around ?lters 33*35, to alloW a
45
omni-directional microphone.
50
55
42 With an adjustable loW frequency ?lter leading to high
pass ?lter 43 (With an adjustable loW frequency roll-o?‘
betWeen 160 HZ and 16 kHZ), and a loW-pass ?lter 44
(having an adjustable loW frequency roll-o?‘ betWeen 40 and
2 kHZ). As in the bass drum equaliZer of FIG. 3, there is a
liThe system alloWs closer placement of the micro
phone to the instrument.
2iThe placement effects an increase in rejection.
3iThe increase reduces or eliminates the need for a
directional microphone, and thus alloWs the use of an
comparison With the original sound.
FIG. 4 is a block diagram of an equaliZer tailor-made for
a snare drum. This equaliZer also has a high-pass input ?lter
directional microphones use to provide the desired cancel
lation), the system has the folloWing advantageous effects
This circuit permits cutting off the strong loW frequency
could otherWise saturate the ampli?er system. From high
pass ?lter 32, the signal passes through high-pass ?lter 33
(having a loW-frequency roll-o?‘ at 10 kHZ), through high
pass ?lter 34 (With an adjustable loW frequency roll-o?‘
betWeen 160 HZ and 12 kHZ), and through loW-pass ?lter 35
microphones are inherently more natural sounding (no phase
cancellations) and can be made signi?cantly smaller (omni
directional microphones do not need the housing Which
4iThe omni-directional microphone can be made
smaller than a directional microphone alloWing even closer
placement to the instrument.
SiThe neW placement provides a further increase in
rejection.
Also, at very close ranges, an omni-directional micro
60
bypass “DRY” path 45.
phone is likely to pick up a more accurate acoustic signature
than a uni-directional microphone (because it “sees” more of
the instrument at a close distance). Because the microphone
can be placed closer to the instrument, the signal-to-noise
ratio of the omni-directional microphone With a tailored
FIG. 5 illustrates a tailor-made equaliZer for a tom-tom.
equaliZing system of the present invention is higher than for
This is a simple circuit having a high-pass ?lter 53 (With a
?xed loW frequency roll-o?‘ at 3.15 kHZ) and a loW-pass
a microphone placed further aWay from the instrument.
A system (especially a digital one) can be built that
?lter 54 (having an adjustable high frequency roll-o?‘
betWeen 40 HZ and 2 kHZ). As in the preceding drum
equaliZers, there is a bypass “DRY” path 55.
65
automatically accomplishes the method of the present inven
tion. The hardWare required is not speci?c to a particular
instrument or even instrument type (except for the micro
US 7,162,046 B2
13
14
phone and attachment mechanism). An embodiment of this
method includes the following steps:
liPlace 2 microphones (Mic 1:system microphone on
most cases the rejection is placed around a center frequency
conceptually. HoWever, in instances Where a large chunk of
mid-range frequencies are rejected, it is sometimes more
desirable to hear and think of tWo pass-band regions rather
or near instrument, Mic 2:reference microphone at a refer
than one stop band. An example is a snare drum, Which has
a sound largely made of tWo portions. The ?rst is a fairly loW
skin and shell resonance someWhere below 1 kHZ (the sound
ence location as previously described).
2iPlay reference sounds of the instrument.
3iHave a processor compare (e.g., via a fast fourier
transform) signals from both microphones.
of the drum With the snares “o?”), and the second is the high
end of the metal snares buZZing against the bottom skin,
perhaps above 4 kHZ. Trying to tune these 2 independent
4iHave the processor create a digital ?lter algorithm
(e.g., FIR) to match the Mic 1 signal to the Mic 2 signal and
store the algorithm.
SiRepeat steps 2, 3, and 4 With different reference
sounds (and store each algorithm).
6iHave the processor “average” the algorithms into a
areas With a parametric band-reject ?lter poses the same
problems of interdependence as in the case of the band-pass
?lter above. In this case separate high and loW frequency
controls are more useful in shaping a signal. FIG. 7 shoWs
hoW a loW pass and high pass may be used in parallel to
create an easily controlled notch function.
?nal algorithm (e.g. FIR).
7iApply the ?nal algorithm to a real time processor,
such as a Digital Signal Processor (DSP).
The foregoing steps can be applied to a speci?c individual
An added advantage of this arrangement is that separate
gain controls can be added to each of the ?lters, so that the
balance of the high and loW pass bands can be varied. FIG.
instrument. To eliminate the need for a user to do this, steps
li7 may be repeated using several different instruments of
the same type (e.g., several violins), and storing the results
of the several averaged algorithms (in step 6). The results of
20
8 shoWs a circumstance Where a snare drum has been tuned
25
to emphasiZe more of the high end snare-buZZ sound. This
is extremely dif?cult or impossible With a parametric equal
iZer.
Referring back to FIG. 4, a block diagram is shoWn that
includes an example of this arrangement in a ?lter designed
the several algorithms can then be “averaged” into a com
posite ?nal algorithm, Which can be used “off the shelf’ by
a user not interested in the effort required to customiZe the
system to a particular instrument. Since it is useful to
provide the same number and range of controls as has been
for a snare drum. Element 43 is a tunable high-pass ?lter
With a volume control. It is shoWn in series With a tunable
determined by the empirical version of the method, these
loW-pass ?lter 44 (a separate volume control is not shoWn).
controls Would alloW the user to tune either version to taste.
The hardWare required to run these algorithms is not speci?c
30
to a particular instrument or even instrument type (except for
The schematic for this is a combination of straightforWard
textbook circuits, and is thus not shoWn in detail here. It
could be imitated on some mixing consoles by sending the
the microphone and attachment mechanism). All that is
original signal to tWo separate channels, then using a tunable
required is that there be enough controls (e.g., knobs that are
data Wheels) for an instrument Which may require the most
manual tuning controls. Thus, various softWare (e.g., pro
grams, data sets, etc.) for different instruments and instru
hi-pass ?lter on channel 1, a tunable loW-pass ?lter on
channel 2, and then mixing the results. This is a very
cumbersome process, and the nature of the acoustical signals
Would have to be Well understood to begin With for the user
to attempt to try. According to an embodiment of the present
invention, this circuit teaches the user to obtain these supe
rior results Without the need to understand any of these
issues beforehand.
It is true that some digital equaliZers (especially on
35
ment types, and even different reference sounds for instru
ments or instrument types, can be supplied on suitable media
(ROM, diskette, etc.). The above described system of the
present invention is a viable implementation of the method,
regardless of Whether the algorithms Were derived as in the
steps above, or Whether an algorithm is created (separately)
to imitate the ?lter elements derived using other methods,
40
sophisticated computer programs and synthesizer-Worksta
tions) alloW the ‘draWing’ of virtually any shape of ?lter or
such as those described elseWhere herein.
It is advantageous, for both accuracy of result and ease of
use, to be able to separately adjust the tWo sides of both a
band-pass ?lter and a band-reject ?lter. This is because in
many circumstances, the choices one makes about the place
ment of the tWo “sides” of a band-pass or band-reject ?lter
are independent.
In the case of a band-pass ?lter in audio Work, for
45
tion, and thus do not speci?cally imply What is accomplished
here. In a digital implementation of the current invention,
this special ?lter combination Would be made available, With
50
example, Where you choose to start rejecting loW frequency
sounds (like hum) has nothing to do With Where you Want to
start rejecting high frequency sounds (like hiss). While a
single parametric band-pass ?lter Will create the shape
needed, any single control will effect both sides; only by
55
frequency or a relatively narroW range, such as feedback
ringing. It is also used to reduce a Wide, shalloW range. In
by the close micing made possible by the invention. The
noise ?oor (inherent noise) of electrical equipment (micro
phones, ampli?ers, equaliZers, etc.) is constant. As the
appreciably higher, Whereas the noise of the components
stays constant. This yields a signi?cantly improvcd signal to
60
noise ratio. In particular, it alloWs the use of a microphone
and associated microphone pre-amp (and other associated
high pass ?lters in series. FIG. 6 shoWs hoW the typical
combination of loW pass and high pass in series yields a
band pass transfer function.
Typically a band-reject ?lter is used to eliminate a single
proper control parameters, as part of a ‘preset’ to the user for
Whatever circumstance Was requested.
As stated above, a further advantage of the present
invention is a large increase in signal-to-noise ratio obtained
method alloWs the microphone to be placed closer to the
sound source than other methods, the signal level becomes
countering the change in one control With a simultaneous
appropriate change in another Will the one side that has been
set rcmain stcady, so the other side can be adjusted inde
pendently. In practice, this is impossible. Some available
equaliZers alloW this by providing separate loW pass and
?lter combination. But these do not ‘teach’ the use of any
proper combination and control of elements for any situa
electronics) that can have a much higher noise level than is
usually tolerated using other methods. This alloWs the
microphone itself to be made smaller and more cheaply
65
(cheaper and perhaps feWer electronics need be included in
the microphone capsule itself), and alloWs for less rigorous
speci?cations for all the equipment described herein.
US 7,162,046 B2
15
16
9. A method for providing a system for high ?delity
reproduction of the acoustic signal from a selected type of
acoustical generator, the method comprising:
I claim:
1. A method for providing a system for high ?delity
reproduction of the acoustic signal from a selected type of
acoustical generator, the method comprising:
(1) determining a selected location proximate to an acous
(1) determining a selected location proximate to a ?rst
5
tical generator;
(2) placing a ?rst microphone at said selected location;
(3) separately generating sounds from the acoustical gen
embodiment of a selected type an acoustical generator;
(2) placing a ?rst microphone at said selected location;
(3) separately generating sounds from the acoustical gen
erator, to produce sounds as picked up by the ?rst
microphone;
erator to produce sounds as picked up by the ?rst
microphone;
(4) playing reference sounds of the acoustical generator;
(5) comparing the sounds of the acoustical generator as
picked up by the ?rst microphone With the reference
sounds as generated by the acoustical generator;
(4) playing reference sounds of the acoustical generator;
(5) comparing the sounds of the acoustical generator as
picked up by the ?rst microphone With the reference
sounds as generated by the acoustical generator;
(6) replacing the ?rst embodiment of the acoustical gen
(6) determining ?rst and second differences in level over
erator of step (1) With a next embodiment of the
?rst and second respective discrete frequency ranges
selected type of acoustical generator:
betWeen the sounds of the acoustical generator as
picked up by the ?rst microphone at the selected
location and the reference sounds as generated by the
acoustical generator;
(7) assembling a ?rst ?lter element, said ?rst ?lter element
including components selected to compensate for said
?rst difference in level over said ?rst discrete frequency
range;
(8) assembling a second ?lter element, said second ?lter
element including components selected to compensate
(7) repeating steps (2) through (5) With the next embodi
20
of tailored ?lter elements to compensate for differences
betWeen the sounds as picked up by the microphone at
25
folloWing: gain adjustment parameter, frequency
discrete frequency range;
elements includes
at least tWo adjustable parameters selected from the
30
folloWing: gain adjustment parameter, frequency
adjustment parameter, bandWidth adjustment
parameter, and ?lter shape adjustment parameter;
and
a single control to make concurrent, predetermined
changes to said at least tWo adjustable parameters;
35
arranging said ?rst and second ?lter elements so as to
12. The method of claim 9 Wherein at least one of
40
13. A system for high ?delity electronic reproduction of
erator, the system comprising:
45
50
55
said ?rst and second ?lter elements has a limited variability
60
gain adjustment of the second ?lter element.
8. The method of claim 1 Wherein at least one of fre
betWeen said ?rst and second ?lter elements.
adjustment parameter, bandWidth adjustment param
eter, and ?lter shape adjustment parameter; and
a single control to make concurrent, predetermined
changes to said at least tWo adjustable parameters.
14. The system of claim 13 Wherein the microphone
element is further adapted to be attached to a preselected
7. The method of claim 1 Wherein a range of gain
adjustment of the ?rst ?lter element differs from a range of
quency-bandwidth, ?lter order, and Q parameters differs
and second ?lter elements to compensate for respective
?rst and second differences in level betWeen the sounds
of the acoustical generator as picked up by the micro
phone at the selected location compared With corre
sponding reference sounds as generated by the acous
tical generator over respective ?rst and second discrete
frequency ranges; Wherein at least one of the ?rst and
second ?lter elements includes
at least tWo adjustable parameters selected from the
folloWing: gain adjustment parameter, frequency
quency-bandwidth, gain, and Q parameters of at least one of
range of operation based on the determining operation of
step 6.
a microphone element adapted to be placed at a speci?ed
selected location proximate to the acoustical generator;
and
an equaliZer that includes an arrangement of at least ?rst
the sounds picked up by the ?rst microphone With reference
sounds of the acoustical generator is made by listening
directly to the tWo sounds.
5. The method of claim 1 Wherein in said constructing
step, the tailored ?lter elements include variable controls.
6. The method of claim 1 Wherein at least one of fre
betWeen said ?rst and second ?lter elements.
the acoustic signal from a selected type of acoustical gen
the sounds picked up by the ?rst microphone With reference
sounds of the acoustical generator is made by listening
directly to the tWo sounds.
4. The method of claim 1 Wherein the step of comparing
a single control to make concurrent, predetermined
changes to said at least tWo adjustable parameters.
10. The method of claim 9 Wherein in said constructing
step, the tailored ?lter elements include variable controls.
11. The method of claim 9 Wherein a range of gain
adjustment of the ?rst ?lter element differs from a range of
frequency-bandwidth, ?lter order, and Q parameters differs
by the acoustical generator.
2. The method of claim 1 Wherein in said placing step,
said ?rst microphone is attached to the acoustical generator.
3. The method of claim 2 Wherein the step of comparing
adjustment parameter, bandWidth adjustment param
eter, and ?lter shape adjustment parameter; and
gain adjustment of the second ?lter element.
(9) constructing an equaliZer for the ?rst microphone by
compensate for the ?rst and second differences betWeen
the sounds as picked up by the microphone at the
selected location and the reference sounds as generated
the selected location and the reference sounds as gen
erated by the acoustical generator; Wherein at least one
of the ?lter elements includes
at least tWo adjustable parameters selected from the
for said second difference in level over said second
Wherein at least one of the ?rst and second ?lter
ment of the selected type of acoustical generator;
(8) constructing a tailor-made equaliZer for the ?rst
microphone, said equaliZer including an arrangement
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location on the acoustical generator.
15. The system of claim 13 Wherein said equaliZer
includes at least one digital ?lter.
US 7,162,046 B2
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16. The system of claim 13 Wherein in said equalizer, the
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18. The method of claim 13 Wherein at least one of
tailored ?lter elements include Variable controls.
frequency-bandwidth, ?lter order, and Q parameters dilTers
17. The method of claim 13 Wherein a range of gain
adjustment of the ?rst ?lter element dilTers from a range of
betWeen said ?rst and second ?lter elements.
gain adjustment of the second ?lter element.
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