`` LEVEL
1
15R
‘Mali/E1665
United States Patent [19]
[11]
Patent Number:
4,612,665
Inami et al.
[45]
Date of Patent:
Sep. 16, 1986
[54]
4,359,601 11/1982 England ............................ .. 381/103
4,504,968 3/1985 Kaneko et a1. .................... .. 381/103
GRAPHIC EQUALIZER WITH SPECTRUM
ANALYZER AND SYSTEM THEREOF
[75] Inventors: Mamoru Inami; Yoshiaki Tanaka,
both of Yokohama’ Japan
[73] Assignee; Victor Company of Japan, Ltd.’
OTHER PUBLICATIONS
R. deJong & L. Simpson; “Playmaster Stereo Graphic
Equalizer”; Electronics Australia; Feb. 1980; vol. 41,
Yokohama, Japan
gokl
‘13;’ PP- 50-30 &h63- 1D isp1 ay”; P ractica1E1 ec
. o lIlSOIl; “ rap ic Leve
[211 APP1-N°~= 314,360
[22] Filed;
tronics; vol. 13, No. 1; Jan. 1977; p. 57.
Oct, 23, 1981
R. Lawrence; “Stereo Digital PPM With LED Dis
play”; Practical Electronics; vol. 12, No. 10; Oct. 1976;
gap-£08416- A d. C l d_ 1 6
302 304
Related US. Application Data
[63]
Continuation of Ser. No. 68,476, Aug. 20, 1979, aban-
cloned‘
[30]
Aug. 21, 1978 [JP]
[51] Int Cl
.
.
.
a 1 -
[56]
’ pp.
GOIR 2 / 8’
.................................. ..
65'67
Primary
Examiner-Gene
Z. Rubinson
,
_
5 0 ;
3//O24
Assistant Examzner-—Randall P. Myers
381 /98_ 324/77 E_
,
Attorney, Agent, or Firm-Michael N. Meller
,
333/28 R; 381/56; 381/103; 381/109
[58]
_
Radio-Electronics; Dec. 1976; vol. 47, No. 12; pp.
Japan ......................... .. 53-114525[U]
.4 ..................... ..
[52] U S Cl
u to ye ope la’ 9 9’ pp‘
“Radio-Electronics Tests Heath AD-l305 Equalizer”;
Foreign Application Priority Data
.
31'2_;T;r.lame’
[57]
Field of Search ........ .. 179/1 B, 1 D, 1 G, 1 GN,
ABSTRACT
179/1 MN, 1 SA, 1 SP, 1 VL; 333/18, 28 R, 28
A graphic equalizer comprises an equalizer for sepa
T, 287; 84/464; 340/753; 381/56, 58, 98, 101,
103, 109; 324/77 B, 77 D, 77 E; 455/158, 159,
177, 200, 233
References Cited
ing out level adjusting of the equalizer, a spectrum
rately level adjusting the input signal for each of a num
ber of divided frequency bands which are different from
each other, control knobs provided one for each of the
divided frequency bands, which are operated for carry
analyzer supplied with the output signal of the equalizer
U.S. PATENT DOCUMENTS
3,676,595
3,732,370
7/1972 Dolansky et al. .............. .. 179/1 SP
5/1973 Sacks .... ..
179/1 D
3,750,044
7/1973
Stanley . . . . . . .
. . . ..
3,892,921
7/ 1975
Burkowitz .
. 179/1 MN
4,118,601
10/1978
Yeap
. . . ..
..... . .... .. .. .
4,176,581 12/ 1979 Stuyvenberg ..
and having a display for displaying the level of each of
the divided frequency bands, and a casing provided
with a panel face having the control knobs and the
display section of the spectrum analyzer disposed in a
corresponding relationship to each other and accommo
179/1 D
179/1
D
dating the equalizer and the spectrum analyzer therein.
84/464 R
4,186,274 l/1980 Mayshar ....... ..
333/28 T
4,307,340 12/1981 Inami et a1. ......................... .. 381/58
11 Claims, 16 Drawing Figures
L'EVEL
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U.S. Patent Sep. 16,1986
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2
ing dispositions. By this arrangement, level adjustment
GRAPHIC EQUALIZER WITH SPECTRUM
can be carried out readily and accurately.
Still another dif?culty arises in certain cases wherein,
even when the frequency characteristics of the signal to
be emitted as sound from the loudspeakers are satisfac
ANALYZER AND SYSTEM THEREOF
This application is a continuation of application Ser.
No. 68,476, ?led Aug. 20, 1979, now abandoned.
tory, the frequency characteristics of the sound emitted
from the loudspeakers and actually reaching the ears of
the listener in the sound ?eld become different from the
BACKGROUND OF THE INVENTION
The present'invention relates to graphic equalizers
above mentioned satisfactory frequency characteristics
with spectrum analyzers and systems thereof and more l0 in accordance with the characteristics of the sound ?eld
including also the characteristics of the loudspeakers.
particularly to a graphic equalizer which is provided
with a spectrum analyzer for displaying the spectrum of
a signal, and which varies and adjusts the level of the
signal for every divided frequency band as the spectrum
display is observed and to a system for employing the
graphic equalizer.
In general, it is desirable in some instances in the
recording of an audio signal, when there is a sound
unpleasant to the ear such as noise or the sound of the
wind of a low constant frequency, to carry out the
15
Accordingly, in accordance with the present inven
tion, means are provided and adapted to make possible
adjustment so that the frequency characteristics of the
actual sound at the listening position of the listener will
become the desired frequency characteristics. For this
purpose, the spectrum of the sound at the listening posi
recording of the audio signal with lowered level of the
tion of the listener is indicatively displayed by the spec
trum analyzer, and level adjustment of the input audio
signal is carried out by the graphic equalizer as the
spectrum thus displayed is observed.
frequency band in which these sounds are present. In
the case where, in a reproducing apparatus, the ?delity
mission characteristic of a signal transmission system is
of the reproduced audio signal is impaired by the effects
known, and it is desired to transform this into a desired
mission characteristic of the listening room, it is desir
able in some instances to correct the level of a certain
frequency band. Furthermore, there are instances
irrespective of frequency band is used in the adjustment
In addition, there are cases wherein only the trans
of characteristics such as the frequency characteristics 25 characteristic. The level of an ordinary input audio
signal is continually ?uctuating in every frequency
possessed by the audio components themselves such as
band. Accordingly, in accordance with the present
the loudspeakers and the pickup cartridge and the trans
where, in both recording and reproducing, the fre
quency characteristics are rendered into desired charac
invention, a pink noise of equal energy distribution
of the transmission characteristic of the signal transmis
sion system to the desired value.
SUMMARY OF THE INVENTION
teristics according to preference without ?attening the
frequency characteristics. In such cases, a graphic 35 Accordingly, it is a general object of the present
invention to provide a novel and useful graphic equal
equalizer capable of variably adjusting the level of the
izer with’spectrum analyzer and a system thereof in
signal for every divided frequency band is used.
which the above described dif?culties and problems
Among graphic equalizers, there are those provided
have been overcome.
with a calibrated scale for indicating the adjustment
Another and specific object of the invention is to
level interrelatedly with the movement of a manipulat 40 provide a graphic equalizer in which is integrally com
ing knob for adjusting the level for every band. In such
bined a spectrum analyzer for indicatively displaying
. a graphic equalizer, however, the degree of level adjust
the spectrum of a signal which has passed through the
ment with respect to the input signal can be determined,
equalizer. By this provision, the level of a desired di
but the level of the signal after level adjustment cannot
vided band part with respect to a signal can be very
be accurately determined.
45 readily and rapidly adjusted as the indication of the
Accordingly, in accordance with the present inven
spectrum analyzer is observed.
tion, a spectrum analyzer is integrally incorporated
Still another object of the invention is to provide a
within a graphic equalizer so that level adjustment can
graphic equalizer with spectrum analyzer in which the
be carried out as the spectrum of the signal after it has
level adjustment manipulative control elements of the
passed through the graphic equalizer is observed. By
graphic equalizer and the indication units of the spec
this organization, since the level adjustment can be
trum analyzer are arranged with corresponding rela
carried out as the level of the signal which has been
tionship.
actually adjusted is observed, the level adjustment can
A further object of the invention is to provide a
be carried out rapidly and accurately.
graphic equalizer with spectrum analyzer capable of
However, when the divided frequency bands which 55 displaying spectrums with respect to signals of a plural
have been level adjusted by the graphic equalizer and
the divided frequency bands indicated by the spectrum
ity of channels with a single spectrum analyzer.
A further object of the invention is to provide a
analyzer are different, accurate level adjustment cannot
be carried out. Accordingly, according to the present
graphic equalizer system wherein the sound emitted
invention, the center frequencies respectively of the
phone at the listening position of the listener and, after
being passed through the equalizer, is caused to be dis
played by the spectrum analyzer, and, as the resulting
display is observed, the level of the input signal in each
of the divided bands is adjusted. By this provision, level
divided frequency bands level adjusted by the graphic
equalizer and the center frequencies respectively of the
divided frequency bands indicated by the spectrum
analyzer are caused to coincide. Furthermore, on the
from the loudspeakers is picked up by means of a micro
face of the manipulative control and indication display 65 adjustment can be carried out in a manner to continu
panel of the apparatus, the level adjustment control
ally obtain a sound of a desirable characteristic at the
elements and the indication display units of the spec
listening position without being affected by the charac
trum analyzer are disposed in respectively correspond
teristics of the audio components such as the loudspeak
3
4,612,665
ers and the pickup cartridge and the characteristics of
4
shown in FIG. 3. When each of the switches 11 and 12
the sound ?eld.
is in a state wherein its movable contact is switched to
An additional object of the invention is to provide a
its contact point a, the input audio signal passes through
graphic equalizer system in which, by supplying pink
can be carried out for every divided frequency band as
the switch 11 to be led out through an output terminal
13 and, at the same time, is fed through the switch 12 to
a spectrum analyzer 14.
the resulting spectrum display is observed. By this pro
vision, adjustment of the signal transmission character
acteristic as indicated in FIG. 2B. In the case where the
istics can be accomplished in a very accurate manner.
?lter of this spectrum analyzer 14 is constituted by a
Other objects and further features of the invention
will be apparent from the following detailed description
with respect to preferred embodiments of the invention
. . . fn of the pass bands of band-pass characteristic are,
noise instead of an input audio signal, level adjustment
This spectrum analyzer 14 has a band-pass ?lter char
é-octave band-pass ?lter, the center frequencies f1, f2, f3,
for example, 16 Hz, 22.4 Hz, 31.5 Hz, 45 Hz, 63 Hz, 90
Hz, 125 Hz, 180 Hz, 250 Hz, 355 Hz, 500 Hz, 710 Hz,
when read in conjunction with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
FIG. 1 is a block diagram of a ?rst embodiment of the
15
1,000 Hz, 1,400 Hz, 2,000 Hz, 2,800 Hz, 4,000 Hz, 5,600
Hz, 8,000 Hz, 11,200 Hz, and 16,000 Hz, (n=20).
The spectrum analyzer 14 per se is well known and is
accommodated within the casing accommodating the
graphic equalizer 15. The levels of the bands of the
above mentioned center frequencies of the audio signal
graphic equalizer with spectrum analyzer according to
the invention;
fed to the spectrum analyzer 14 are displayed at a dis
FIGS. 2A and 2B are graphs respectively indicating
the frequency level characteristics of a graphic equal
izer and the ?lter characteristics of a spectrum analyzer;
FIGS. 3 and 4 are front views respectively showing
play section 22 on the panel face 20. In this display
section 22, a plurality of light-emitting elements are
vertically alined for each of the above mentioned bands.
These light-emitting elements carry out light-bar or
examples of panel faces used in the graphic equalizer
light-spot displaying in response to the display levels.
By merely observing the display section 22, the user
of the sound apparatus can readily perceive the bands of
the input audio signal whose levels differ from their
respective desired levels.
Upon level adjusting, the user manipulates the switch
shown in FIG. 1;
FIG. 5 is a block diagram of a second embodiment of
the graphic equalizer with spectrum analyzer according
to the invention;
FIG. 6 is a front view of one example of a panel face
used in the graphic equalizer illustrated in FIG. 5;
FIG. 7 is a block diagram of a third embodiment of
the graphic equalizer with spectrum analyzer according
to the invention;
FIG. 8 is a schematic diagram for a description of the
state in which sound reproduced by loudspeakers is
picked up by a microphone in a system in which the
graphic equalizer of FIG. 7 is employed;
knob 21 to switch the movable contacts of the switches
11 and 12 over to their respective contact points b. The
input audio signal introduced through the input termi
nal 10 thereupon is fed through the switch 11 to a
graphic equalizer 15. The resulting output signal of this
equalizer 15 is led out through the output terminal 13
and, at the same time, is fed by way of the switch 12 t0
the spectrum analyzer 14. At this time, the states of the
the graphic equalizer with spectrum analyzer according
levels of all bands of the audio signal after being level
adjusted by the equalizer 15 are displayed at the display
section 22 of the spectrum analyzer 14.
The panel face 20 is also provided with a manipula
to the invention;
tive control section 23 provided with control knobs 23a,
FIG. 9 is a front view of one example of a panel face
used in the graphic equalizer shown in FIG. 7;
FIG. 10 is a block diagram of a fourth embodiment of
FIG. 11 is a diagram of one embodiment of a block
23b, . . . 23n as shown in FIG. 3. The levels of the vari
system which is in an even more concrete form of the 45 ous bands of the graphic equalizer 15 are variably con
block system shown in FIG. 10;
trolled as indicated in FIG. 2A by manipulation of these
FIGS. 12A and 12B are respectively a front view of
the panel face of the apparatus shown in FIG. 11 and an
knobs 23a, 23b, . . . 23n. More speci?cally, by the manip
FIG. 13 is a diagram indicating one example of con
nection of the graphic equalizer in a system in which the
divided bands are increased or decreased. The maxi
mum quantities of this increase and decrease are respec
graphic equalizer of FIG. 11 is employed; and
tively designated by +MAX and —MAX. The equal
ulation of the knobs 23a through 23n, the signal levels of
enlarged view of the display part of the spectrum analy
the divided bands having equal center frequencies at the
50 center frequencies f1 through f,, of the above mentioned
zer;
FIG. 14 is a circuit diagram of one embodiment of the
izer 15 is so adapted that it is level adjusted by the up
circuit in concrete form of the equalizer illustrated in 55 and-down movements of the knobs 23a through 23n.
FIG. 11.
The positions of these knobs in their ranges of move
ment are indicative of their respective quantities of level
adjustment. Accordingly, calibrations of the same unit
The ?rst embodiment of the graphic equalizer with
(for example, decibel (dB)) as the display section 22 are
spectrum analyzer according to the present invention 60 inscribed on the panel face alongside these knobs.
will ?rst be described with reference to FIG. 1. An
The user manipulates the knobs 23a through 23m as he
audio signal applied to an input terminal 10 is supplied
observes the display section 22 of the spectrum analyzer
to the movable contact of a switch 11 and a ?xed
14 and carries out level adjustment so that the levels of
DETAILED DESCRIPTION
contact point a of a switch 12. These switches are
switched synchronously or interrelatedly, for example,
the various divided bands indicated at the display sec
65 tion 22 assume their desired states. As a result, a signal
by the manipulative actuation of a switch knob 21 pro
thus level adjusted with its frequency characteristics
vided on a panel face 20 of a casing which accommo
adjusted as desired is led out through the output termi
nal 13.
dates a spectrum analyzer and a graphic equalizer as
5
4,612,665
While the display section 22 is disposed directly
above and in vertical alignment with the control section
23 in the example illustrated in FIG. 3, these sections 22
and 23 may be disposed side-by-side as, for example, in
the example shown in FIG. 4. In FIG. 4, those parts
either of the signals of the left and right channels also
must not exceed the maximum saturation level. For this
reason, a maximum level selector is used instead of the
adder 31 as mentioned above.
which are the same as corresponding parts in FIG. 3 are
respectively designated by like reference numerals.
Description of these parts will be omitted.
In each of the panel faces shown in FIGS. 3 and 4, the
display of the divided bands of the display section 22
and the knobs 23a through 23n are disposed in respec
tively corresponding arrangement. For this reason,
surveillance of the level display and manipulative con
The operation in the case where the switch 21 is
manipulated to switch the movable contacts of the
switches 11R, 11L, 12R, and 12L respectively over to
their contact points b can be readily understood from
trol of the levels can be carried out easily and accu
rately.
The second embodiment of the graphic equalizer
according to the invention will now be described in
conjunction with FIG. 5. In the case where the above
6
at the time of recording on a tape, for example, it is
necessary to control the peak value of the signal level so
that it does not exceed the saturation level, the level of
15
the foregoing description, and therefore description of
this operation will be omitted. Level adjustment of the
equalizers 15R and 15L is accomplished by up-and
down sliding adjustment manipulation of the control
knobs 230 through 23n. In the present embodiment of
the invention, the level adjustment is carried out simul
taneously with respect to the two equalizers 15R and
described preceding embodiment of the invention is
15L by a common single set of control knobs 23a
used as it is for multiple-channel signals, the circuit of 20 through 23n. For this reason, the organization of the
the block system shown in FIG. 1 is required in the
apparatus is simple, and its size can be made small. In
corresponding plural number. In this case, simultaneous
the case where it is desirable to level adjust the equaliz
surveillance of the display sections of the plural number
ers 15R and 15L separately, separate sets of control
of spectrum analyzers is dif?cult. Other problems such
knobs respectively for exclusive use for the equalizers
as the dif?culty of keeping the size of the apparatus 25 15R and 15L are provided as in the embodiment of the
small and high cost also arise. Accordingly, in the pres
invention described hereinafter.
ent embodiment of the invention, these problems are
In each of the above described preceding embodi
overcome by a circuit organization wherein displaying
ments of the invention, supplying is carried out to dis
can be carried out by using one spectrum analyzer for
play by switching, to the spectrum analyzer 14, the
multiple-channel signals as, for example, two-channel
stereo signals. In FIG. 5, those parts which are the same
input audio signal itself and the input audio signal which
has passed through an equalizer. However, the signal of
as corresponding parts in FIG. 1 are designated by like
the sound emitted from the loudspeakers in the sound
reference numerals, to which subscripts R and L are
?eld of the listening room and actually reaching the ears
appended to indicate respectively right and left channel
of the listener and the input audio signal are not neces
signal systems.
35 sarily identical due to effects of characteristics of speak
When switches 11R, 11L, 12R, and 12L are in their
ers, and sound transmission characteristic of a listening
states wherein their movable contacts are respectively
room etc. Accordingly, it is desirable that the above
in contact with their contact points a, as illustrated in
described level adjustment is carried out with the sound
FIG. 5, right and left channel input audio signals intro
actually reaching the ears of the listener as a standard.
duced through input terminals 10R and 10L pass re 40 An embodiment of the invention in which this has
spectively through the switches 11R and 11L and are
been realized will now be described with reference to
led out through output terminals 13R and 13L. At the
FIGS. 7, 8, and 9. In FIGS. 7 and 9, those parts which
same time, these right and left channel input audio sig
are the same as corresponding parts in FIGS. 5 and 6 are
nals are fed by way of the switches 12R and 12L and
designated by like reference numerals. Description of
further by way of closed switches 30R and 30L to an 45 such parts will be omitted.
adder 31, where they are combined into a single signal.
Referring ?rst to FIG. 7, input audio signals of right
The resulting output signal of the adder 31 is fed to a
and left channels entering through input terminals 10R
spectrum analyzer 14 and displayed in the display sec
and 10L pass through equalizers 15R and 15L and are
tion 22 of a panel face 32 as shown in FIG. 6.
led out through output terminals 13R and 13L. Then,
> Thus, according to the present embodiment of the 50 when the movable contact of a switch 43 is connected
invention, the right and left channel signals are com
to a contact point a thereof, the output signal of the
bined and then displayed. For this reason, a single spec
equalizers 15R and 15L are supplied through switches
trum analyzer is sufficient. Therefore, surveillance of
30R and 30L to an adder 31 similarly as in the preceding
the spectrum is facilitated, the apparatus can be made
embodiment of the invention, and the resulting output
small and compact.
55 signal of the adder 31 is fed to a spectrum analyzer l4
In the case where the displaying of only the right
and is displayed in the display section 22 of a panel face
channel signal is to be carried out, a switch knob 33L on
the panel face 32 is manipulated to open the switch 30L.
Similarly, when displaying of only the left channel sig
50 as shown in FIG. 9.
The signals led out through the output terminals 13R
and 13L are applied to terminals 44R and 44L shown in
nal is to be carried out, a switch knob 33R is manipu 60 FIG. 8 and supplied through ampli?ers 45R and 45L to
lated to open the switch 30R.
loudspeakers 46R and 46L, which thereby emit corre
In the present embodiment of the invention, instead
sponding sounds. In a sound ?eld 49 formed by the
of the adder 31, a maximum level selector which selec
sounds from the loudspeakers 46R and 46L within a
tively produces as output the channel signal of higher
listening room, a microphone 47 is placed in the listen
level of the input right and left channel signals may be 65 ing position of a listener thereby to pick up the sounds
used. In the case where surveillance of the variation of
from the loudspeakers 46R and 46L. The audio signal
the averaged sound volume of the input signals is neces
from the microphone 47 is applied through a terminal
sary, the above described adder is used. However, when
48 to a terminal 40 as shown in FIG. 7.
7
4,612,665
The signal thus applied to the terminal 40 is passed
8
uniform over the entire frequency band and this makes
through an ampli?er 41 and is applied, on one hand, by
it possible to instantly recognize the overall transfer
way of an attenuator 42 to a contact point b of the
frequency characteristics and to carry out the level
adjustment over the entire frequency range very
aforementioned switch 43 and, on another hand, di
rectly to a contact point 0 of the same switch 43. By
manipulating a switch knob 51 on the panel face 50 and
connecting the movable contact of the switch 43 to its
contact point b or c, the audio signal from the micro
phone 47 is supplied to the spectrum analyzer 14 and
displayed in the display section 22. When the movable
quickly.
Next, a description of a more concrete form of the
graphic equalizer provided with spectrum analyzer
indicated in FIG. 10 is given in conjunction with one
embodiment shown in block diagram in FIG. 11. Parts
in FIG. 11 which corresponds to parts in FIG. 10 are
Accordingly, by carrying out level adjustment by
designated by like reference numerals. As the left-chan
nel equalizer 15L is identical with the right-channel
equalizer 15R, it is not illustrated in detail in the ?gure
and description thereof is omitted here.
When the spectrum of the input signal is to be dis
played on the spectrum analyzer 14, pink noise switch
independently manipulating control knobs 23Ra
through 23Rn and 23La through 23Ln of the equalizers
knobs 91R and 91L disposed on a panel 90 shown in
FIG. 12A are set to OFF position. This puts a switch 70
contact of the switch 43 is connected to its contact point
b, and the display in the display section 22 exceeds the
maximum display level, the switch 43 is switched to its
Contact point 0 thereby to supply the signal attenuated
15
by the attenuator 42 to the spectrum analyzer 14.
15R and 15L as the display in the display section 22 is
in a position which allows the signal introduced from
observed, optimum level adjustment with respect to all 20 the input terminal 10R to pass therethrough. Another
channels can be carried out in accordance with the
switch knob 92 is set to ON, putting a switch 71 in a
actual state at the listening position of the listener in the
position which causes the signal from the switch 70 to
sound ?eld.
pass to a switch 72 and then pass from the switch 72 to
In this connection, the microphone 47 may be in
the output terminal 13R. Moreover, when a switch
stalled in a built-in state in the pannel 50. Furthermore, 25 knob 93 is set to ON, the switch 72 passes the signal
the number of channels is not limited to two.
from the switch 71 to a buffer ampli?er 73 and passes
A fourth embodiment of a graphic equalizer provided
the signal from a relay 75 to the switch 71. When the
with a spectrum analyzer according to the present in
input signal is abnormally large the knob 93 is set to the
vention will be described in conjunction with FIG. 10.
-6 dB position, whereby the input signal level is atten
In FIG. 10, those parts which are the same as corre 30 uated to one half. Further, when a microphone switch
sponding parts in FIG. 7 are designated by like refer
ence numerals. Detailed description of such parts will
be omitted.
For level adjustment operation, the present embodi
knob 94 is set to OFF, a switch 77 is changed to a posi
tion which allows the output signal of the adder 31 to
pass therethrough.
The input audio signal introduced through the input
terminal 10R passes successively through the switches
ment is adapted to use a pink noise instead of an input 35
audio signal. Since pink noise has an energy distribution
70, 71, and 72 and is then fed to the buffer ampli?er 73.
which is always uniform over the entire frequency
The output signal of the ampli?er 73 is supplied to an
band, level adjustment can be accomplished more accu
equalizer 74 described later, where it is level adjusted
rately than in the case of employing an audio signal
for each divided frequency band. The level-adjusted
having a constantly ?uctuating level.
40 signal passes through the relay 75 and then the switch
Referring to FIG. 10, a pink noise generator 60 gener
71 and is led out through the output terminal 13R. The
ates pink noise which is supplied through switches 61R
relay 75 is normally closed and is opened at the time
and 61L to the equalizers 15R and 15L respectively. At
when the muting circuit 85 is in operation.
The output signal passed from the switch 71 and led
this time, there is, of course, no audio signal applied to
the input terminals 10R and 10L. The pink noise signal
out through the terminal 13R is supplied through the
which has passed through the equalizers 15R and 15L is
switch 30R to the adder 31, where it is added with the
emitted from the speaker as sound, which is picked up
left-channel signal being supplied thereto by way of the
by a microphone and is displayed on the display section
switch 30L. The resulting output signal passes through
22 of the spectrum analyzer 14. While observing this
the switch 77 and a variable resistor 78 for level adjust
display, the operator adjusts the level for each of the 50 ment which is controlled by a knob 95, and is then
divided frequency bands by means of the equalizers 15R
supplied to a pre-ampli?er 79.
and 15L. This level adjusting operation is exactly the
same as that in the above described embodiment.
The resulting output signal from the pre-ampli?er 79
is supplied to a ?lter 80, where it is frequency divided
into speci?c frequency band signals which are then
In the pink noise generator 60, the pink noise is gener
ated by the well-known method of passing white noise 55 supplied to a display driving circuit 81. Accordingly,
through a pink noise ?lter.
each signal is displayed by bar-graph indication 100 on
When level adjustment is to be carried out indepen
the display section 22 shown in FIG. 12B. On the other
dently for the right- and left-channels, the following
procedure is used. The switch 61R is closed causing
pink noise to emit from the right-channel speaker and
the level is adjusted for the right-channel. Then, the
switch 61R is opened and the switch 61L is closed and
the level is adjusted for the left-channel. The adjustment
may, of course, be made in reverse order.
hand, the signal from the pre-ampli?er is supplied by
way of an attenuator 82 and a pre-arnpli?er 83 to the
display driving circuit 81. On the display section 22
shown in FIG. 12B, a bar-graph indication 101 shows
the level for the full range (the overall frequency band).
The above described display operation is carried out,
for example, with the components electrically con
In the above described level adjusting operation, it is 65 nected as indicated in FIG. 13. Either a record player
possible to use a signal reproduced from a frequency
record or a warble tone instead of pink noise. However,
the use of pink noise is preferred, because pink noise is
110 or a tuner 111 is connected to a pre-main-ampli?er
112. The pre-main-ampli?er 112 is connected to the
input terminal 10 and the output terminal 13 of the
4,612,665
10
graphic equalizer provided with the spectrum analyzer
of the present invention. The output terminals of the
pre-main-ampli?er 112 are connected to the speakers
46R and 46L.
With the components connected as described above,
control control
knob 96 knob 92
the operator vertically slides the respective control
(switch (switch
signal at terminal
76)
71)
87R
13R
OFF
OFF
input signal from
input signal
terminal 10R
control knob 93
control knob 93
knobs in control knob sections 23R and 23L while ob
serving the display section 22. Accordingly, the output
of the equalizer 74 is adjusted for each divided fre
(switch 72)
(switch 72)
inoperational
capable of ON-OFF
input signal
reproduced signal
control knob 93
from terminal 86R
control knob 93
operation
quency band so that the speakers 46R and 46L are made
ON
capable of producing sound having the desired charac
teristics.
OFF
When the frequency characteristics of the sound at a
particular listening position are to be adjusted, the mi
crophone 47 is connected to the terminal 40, and the
knob 94 is set to ON position. This causes the switch 77
to change to a position which allows the signal from the
signal at terminal
15
ON
ampli?er 41b to pass therethrough and puts the switch
84 in a position which allows the signal from the ampli 20 OFF
?er 41a to pass therethrough as it is.
When the level of the signal from the microphone 47
is too high, the control knob 94 is set to the —20 dB
position and the level of the signal passing through the
25
switch 84 is attenuated by --20 dB.
The sound signal from the speakers 46R and 46L
ON
ON
(switch 72)
(switch 72)
inoperational
capable of ON-OFF
input signal
operation
reproduced signal
control knob 93
control knob 93
(switch 72)
(switch 72)
capable of ON-OFF
inoperational
operation
input signal
input signal
control knob 93
control knob 93
(switch 72)
(switch 72)
capable of ON-OFF
capable of ON-OFF
operation
operation
Particularly in the case of recording on a cassette
tape, there is a tendency for the signal to distort at
picked up by the microphone 47 is introduced through
higher
frequencies. Accordingly, to avoid signal distor
the terminal 40 and then passes through the ampli?er
tion it is preferrable to record with the level attenuated
410, the switch 84, and the ampli?er 41b. The signal
by -—2 dB at 8 KHz and by —4 dB at 16 KHz and to
from the ampli?er 41b passes through the switch 77 and
reproduce with the level increased by +2 dB at 8 KHz
is supplied by way of the variable resistor 78 to the
and by +4 dB at 16 KHz. Conversely, in order to lower
spectrum analyzer 14, where it is level displayed on the
tape hiss noise, signals above 4 KHz can be recorded
display section 22 thereof. The operator adjusts the
with the level increased by +4 dB and reproduced with
level in the equalizer while observing the display sec 35 the level attenuated by —4 dB.
tion 22.
FIG. 14 shows the concrete circuit con?guration for
When pink noise is to be used instead of an input
one embodiment of the above described equalizer 74. In
audio signal as the signal emitted from the speakers, the
the same ?gure, the signal from the switch 72 is intro
switch knobs 91R and 91L are set to their ON positions.
duced through an input terminal 120 and is supplied by
This allows the switch 70 to pass the pink noise from the
way of the DC buffer ampli?er 73 and a resistor 121 to
pink noise generator 60. Accordingly, instead of the
input audio signal, the pink noise passes through the
a DC ampli?er 122. Variable resistors 123-1, 123-2, . . .
switch 70, and then further passes through the switches
71 and 72, and is thereafter supplied to the buffer ampli
?er 73. Thereafter, similarly as in the preceding case,
the pink noise is led out through the output terminals
DC ampli?er 122. Between sliders of the variable resis
, 123-10 in parallel connection are connected across the
tors 123-1, 123-2, . . . , 123-10 and the ground are respec
45 tively connected resonance circuits 124-1, 124-2, . . . ,
124-10, each of which comprises a resistor, a capacitor,
13R and 13L (13) and is then emitted as sound from the
and a coil connected in series.
speakers 46R and 46L.
For independent level adjustment of the right- and
trum analyzer 14 is an octave band-pass ?lter whose
In the present embodiment, the ?lter 80 in the spec
left-channels, one or the other of the control knobs 91R 50 central frequencies f1, f2, . . . , fro of the respective di
vided frequency bands are set to 31.5 Hz, 63 Hz, 125 Hz,
and 91L is set to ON position.
Here, the microphone 47 is directed along a line bi
secting the angle formed between the speakers 46R and
46L and itself. In carrying out the level adjustment for
each channel, it is not necessary to direct the micro
phone 47 toward the speaker which is emitting sound.
The microphone 47 needs not be a two-channel micro
phone and any monaural microphone may be used.
Terminals 86R and 86L are input terminals through
which the reproduced signal from a tape deck 114 is
introduced. Other terminals 87R and 87L are output
terminals through which a signal to be recorded by the
tape deck 114 is led out. The switch 76 is changed over
by the operation of the switch control knob 96.
The table below shows the relationship between the '
on-off state of the control knobs 92 and 96 and the signal
derived from the terminals 87R and 13R.
250 Hz, 500 Hz, 1 KHz, 2 KHz, 4 KHz, 8 KHz, and 16
KHz. The resonance frequencies f1, f2, . . . , flo of the
resonance circuits 124-1, 124-2, . . . , 124-10 are set to
coincide with the central frequencies f1 through f10. The
variable resistors 123-1 through 123-10 are adjusted by
manipulating the control knobs 23R1, 23R2, . . . , 23R10
on the control section 23R. As a result of this adjust
ment of the variable resistors 123-1 through 123-10, the
signals of the respective divided frequency bands are
independently level adjusted with the frequencies f1
through flo as their center frequencies. These indepen
dently level adjusted frequencies are led out by way of
a capacitor 125 and an output terminal 126, and are then
65 sent to the relay 75.
The con?guration and operation of the circuit of the
equalizer for the left-channel system are the same as the
above and description thereof will be omitted.
11
4,612,665
12
(b) level adjustment of said second equalizer is car
Moreover, in the spectrum analyzer 14, the amount of
ried out by said control means;
attenuation in the attenuator 82 is selected to be such
(0) ?rst signal processing means is provided for selec
tively outputting to said spectrum analyzer at any
given point in time either said ?rst output signal,
that, when pink noise is being displayed on the display
section 22, the level of the entire frequency band of the
pink noise passed through the attenuator 82 and dis
played by the full range indication 101 is equal to the
levels of each of the divided frequency bands pink noise
indicated by each of band indications 100. In the present
said second output signal, or a sum of said ?rst and
second output signals in response to a mode selec
tion switch operated manually.
4. A graphic equalizer as in claim 3 wherein said ?rst
signal processing means comprises an adding circuit for
obtaining the sum of said ?rst and second output signals,
and switching means for selectively outputting to said
embodiment, the amount of attenuation in the attenua
tor 82 is set to around 18 dB. Accordingly, in the equal
izer adjusting operation by sliding the control knobs on
the control sections 23R and 23L, the level of indication
100 coincides with the level of indication 101 on the
spectrum analyzer either said ?rst output signal, said
second output signal, or said sum of said ?rst and sec
display section 22. Consequently, the adjusting opera
ond output signals.
tion can be carried out with ease. The signal processing
means may be in the form of a maximum level selector
5. A graphic equalizer as in claim 3 wherein the cen
ter frequencies of the respective divided frequency
adapted to pass the signal having the greatest amplitude
bands in said ?rst and second equalizers are respectively
substantially equal to the center frequencies of the re
spective divided frequency bands in said spectrum ana
among a plurality of signals.
Further, this invention is not limited to these embodi
ments but various variations and modi?cations may be
lyzer.
made without departing from the scope of the inven
tion.
What is claimed is:
6. A graphic equalizer as in claim 3 wherein:
(a) a ?rst speaker is supplied with said ?rst output
signal and emits said ?rst output signal as sound;
(b) a second speaker is supplied with said second
output signal and emits said second output signal as
1. A graphic equalizer comprising:
(a) a ?rst equalizer for separately level adjusting a
?rst input signal for each of a number of divided
sound;
frequency bands, producing a ?rst output signal,
(c) a microphone picks up the sound emitted by said
said divided frequency bands being different from
each other;
?rst and second speakers and propagated through a
sound ?eld; and
(d) second signal processing means is provided for
inputting the signal from said microphone to said
(b) control means, one for each of said divided fre
quency bands, for carrying out level adjusting of
said ?rst equalizer;
(c) control knobs provided one for each of said
spectrum analyzer.
7. A graphic equalizer as in claim 6 wherein said
divided frequency bands for manually controlling
second signal processing means comprises __n ampli?er,
said control means;
35 an attenuator, and switching means means for supplying
the input terminal of said spectrum analyzer with either
(d) a spectrum analyzer having a display section for
the output signal of said ?rst signal processing means or
separately displaying said ?rst output signal for
the output signal of said ampli?er or the output signal of
each of a number of divided frequency bands,
said attenuatorv
wherein said divided frequency bands are the same
8. A graphic equalizer as in claim 3 wherein said ?rst
and second input signals are generated by a pink noise
generator.
9. A graphic equalizer according to claim 3, wherein
frequency bands for which said ?rst input signal is
level adjusted in said ?rst equalizer; and
(e) a casing provided with a panel face having said
control knobs and said display section of said
spectrum analyzer and accommodating said ?rst
equalizer and said spectrum analyzer therein, said
control knobs being positioned on said panel face
in correspondence with said display section for
each of said divided frequency bands.
2. A graphic equalizer according to claim 1, wherein
said control means comprises ?rst and second control
45 means, one for each of said ?rst and second equalizers,
said equalizer comprises a buffer ampli?er, a ?rst resis
tor, a dc ampli?er, and a capacitor connected in series
between the input and output terminals, said do ampli
?er having a ?rst and a second input terminal and an
output terminal; a second resistor coupled to said sec
ond input terminal and said output terminal; a plurality
of variable resistors coupled in parallel to said ?rst and
second input terminal of said do ampli?er, each of said
variable resistors being coupled to a common reference
respectively, for carrying out level adjusting of said ?rst
and second equalizers.
10. A graphic equalizer according to claim 1, wherein
switching means is provided for switching and supply
ing said ?rst input signal to said spectrum analyzer
when carrying out said level adjusting of said ?rst
equalizer by said control means.
11. A graphic equalizer according to claim 1,
wherein:
(a) a second equalizer is provided for separately level
adjusting a second input signal for each of a num
ber of divided frequency bands, producing a sec
ond output signal, said divided frequency bands
being the same frequency bands into which said
potential; and a plurality of tuned circuits, each of
?rst input signal was divided by said ?rst equalizer;
which is coupled to the slider of one of said variable
resistors and to a reference potential.
(b) level adjustment of said second equalizer is car
ried out by said control means;
(c) ?rst signal processing means is provided for selec
tively outputting to said spectrum analyzer at any
given point in time either said ?rst input signal, said
second input signal, or sum of said ?rst and second
3. A graphic equalizer according to claim 1, wherein:
(a) a second equalizer is provided for separately level
adjusting a second input signal for each of a num
ber of divided frequency bands, producing a sec 65
ond output signal, said divided fequency bands
being the same frequency bands into which said
?rst input signal was divided by said ?rst equalizer;
input signals in response to a mode selection
switch.
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