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DESCRIPTION JPH1069280

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DESCRIPTION JPH1069280
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
sound field control unit which enhances sound effects such as volume feeling, reverberation and
spread feeling by electro-acoustic means based on existing room sound conditions and supports
the sound field. And a sound field control device, which facilitates the introduction of the sound
field support system.
[0002]
2. Description of the Related Art As an electroacoustic realization of control such as
reverberation extension based on existing room acoustic conditions, there has been an acoustic
feedback system whose principle is shown in FIG. The speaker 12 and the microphone 14 are
disposed at an appropriate distance in the chamber 10, and the sound collected by the
microphone 14 is supplied to an FIR (Finite Impulse Response: non-recursive) filter 18 through
the head amplifier 16. Generation of a reverberation signal (mainly an initial reflection sound
signal), outputting this to the speaker 12 via the amplifier 20, and repeating sound collection to
increase the sense of volume (increase in sound pressure level), It is intended to increase the
sense of reverberation (increase of reverberation time) and increase of sense of spread (increase
of side reflection sound energy). According to this, it is possible to create a feeling of sound like
playing in a large space such as a hall while being a room 10 in a small space.
[0003]
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1
A conventional sound field control apparatus using this acoustic feedback system is shown in
FIG. 3 and FIG. FIG. 3 shows the arrangement of the microphones and the speakers. In the room
22 such as a music room, four microphones 24 to 27 are installed on the ceiling and four
speakers 30 to 33 are installed on the wall. There is. An apparatus main body 36 that controls
the whole is configured as an independent apparatus and installed in the room 22.
[0004]
FIG. 4 shows a circuit configuration. The collected sound signals of the microphones 24 to 27
have their frequency characteristics adjusted to prevent howling by the equalizer 42 through the
head amplifiers 38 to 41, and the FIR filter 44 initially The reflected sound is generated,
amplified by the amplifiers 46 to 49, and reproduced from the speakers 30 to 33. The ROM 52
stores initial reflection sound parameters of various sound field patterns. When a sound field
pattern selection operation is performed by the external infrared remote control transmitter 54,
the corresponding sound field pattern selection signal 56 is transmitted and received by the light
receiving window 58 of the apparatus main body 36. In response to this, the CPU 60 reads the
initial reflection sound parameter of the corresponding sound field pattern from the ROM 52 and
sets it in the FIR filter 44 to set the sound field space.
[0005]
Adjustment of the frequency characteristic by the equalizer 42 is performed, for example, by any
of the following methods. (A) The equalizer 42 is configured by an FIR filter, and the
characteristics of the room are measured in advance, the characteristics of the FIR filter are
preset to the inverse characteristics of the room, and the collected signals of the microphones 24
to 27 are convoluted with the FIR filter Calculate to flatten the frequency characteristics. (B) The
equalizer 42 is configured by a notch filter, and when howling occurs in actual use, at that time,
the frequency band where the howling occurs is subjected to a notch filter to suppress the
howling. (C) The equalizer 42 is configured by a graphic equalizer, and a person manually adjusts
the graphic equalizer while measuring the characteristics of the room to flatten the frequency
characteristics.
[0006]
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SUMMARY OF THE INVENTION In the conventional sound field control apparatus using acoustic
feedback, in order to ensure the stability against howling, the installation place of the
microphone and the speaker each time the space (room) changes. It was common to reset it. At
that time, the microphone and the speaker were of course at different positions and the distance
was also changed for each space. In addition, for adjustment after installation, open loop gain
adjustment and transmission frequency characteristic adjustment are performed for each
microphone / speaker combination with a special measuring instrument, and then the presence
of howling and coloration on sound quality are confirmed. The For this reason, installation and
adjustment take a long time, which has been a hindrance in introducing a sound field support
system.
[0007]
Further, among the adjustment methods of the frequency characteristics by the equalizer 42, the
method by the FIR filter requires a sophisticated calculation means in order to process a huge
amount of calculation. Also, the method using the notch filter can not prevent howling in advance
because the method actually copes with howling. Furthermore, when a large number of peaks of
frequency characteristics causing howling exist over a wide band, a large number of notch filters
are required. In addition, the method using the graphic equalizer requires a great deal of effort
because it is adjusted manually.
[0008]
This invention solves the problem in the said prior art, and tends to provide the sound field
control unit and sound field control apparatus which made introduction of a sound field
assistance system easy.
[0009]
According to the present invention, at least a microphone, a speaker, a pickup signal switching
means, an equalizer, an FIR filter, and an amplifier are integrally incorporated into a unit, and a
plurality of units are mutually connected via a transmission cable. It is something that can be
done.
The sound pickup signal of the other unit is supplied from the transmission cable, and the sound
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3
pickup signal of the own unit and the sound pickup signal of the other unit are sequentially
switched by the sound pickup signal switching means, so that the connection state of the
microphone and the speaker is between the plural units. You can switch between them. As a
result, the transmission characteristics between the microphone and the speaker are averaged to
reduce the coloration and enlarge the howling margin. Therefore, even if the distance between
the speaker and the microphone is fixed in one unit, coloration and howling do not easily occur,
and automation of adjustment of loop characteristics also becomes easy. Moreover, installation is
easy because it is unitized.
[0010]
Also, by continuously and randomly changing the parameters of the FIR filter on the time axis,
the frequency characteristics of the FIR filter can be averaged, and coloration and howling can be
made more difficult to occur.
[0011]
In addition, if each unit is provided with an infrared light receiving unit and configured to
transmit the remote control signal received by one of the units to the other unit via the
transmission cable, remote control operation is performed in a wide range of the room. The
operability is improved.
[0012]
As the structure of the unit, for example, the case is vertically erected on the floor and installed
on the floor, and the speaker is radiated into the case so as to radiate the sound upward from the
upper end opening of the tube constituting the case. The microphone is installed on the side of
the case to pick up the sound around the case, the electric circuit part is installed in the case, and
the sound pickup signal input / output terminal can be connected to the transmission cable from
the outside It can be installed at the site.
If the housing is formed into a tubular shape in this manner, the distance between the speaker
and the microphone can be increased. Furthermore, since the direction of the speaker and the
direction of the microphone are different, the sound reproduced by the speaker of the own unit is
The amount of direct routing to the unit's microphone can be reduced, making it more difficult
for howling to occur.
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[0013]
Further, the equalizer is constituted by a front equalizer provided between the sound pickup
signal switching means and the FIR filter, and a rear equalizer provided between the FIR filter
and the amplifier, and a rear stage of the rear equalizer By providing an attenuator, it is possible
to automatically adjust the equalizer and attenuator before and after the measurement reference
signal and the transmission characteristic measurement means.
In this automatic adjustment, the output of the sound pickup signal switching means is fixed to
the sound pickup signal of the own unit, and any part of the signal path is cut off to set an open
loop state, and the reference signal for measurement from the cut off point And the frequency
characteristic of the signal picked up by the microphone of the own unit and fed back to the cutoff point is measured by the measuring means, so that the frequency characteristic becomes a
predetermined flat characteristic. Adjust the characteristics of the equalizer on the side and then
adjust the attenuator in the open loop state to adjust the gain of the loop to a predetermined
value, close the loop, and execute the switching operation of the sound pickup signal switching
means While the measurement reference signal is fed into the loop, the measurement means
measures the frequency characteristic of the loop, and the front equalizer characteristic is
adjusted so that the frequency characteristic becomes a predetermined flat characteristic.
Consisting of adjustment in the closed loop state to adjust.
[0014]
The rear side equalizer can be configured by a parametric equalizer that can set the center
frequency, gain, and Q. The automatic adjustment in that case can be performed, for example, as
follows. That is, the measured frequency characteristic is compared with a predetermined target
gain, and the peak frequency of the portion above the target gain on the frequency characteristic,
the difference between the gain at the peak frequency and the target gain, and the peak
frequency of the portion The frequency of the intersection at which the target gain crosses with
the target gain is detected on both sides, and the sharpness of the characteristic at that point is
determined from the peak frequency, gain difference and intersection frequency, and the
detected or determined peak frequency, gain difference, Set the center frequency, gain, and Q of
the rear equalizer to match the sharpness.
[0015]
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Also, as the front equalizer, it is possible to configure a parametric equalizer in which the center
frequency and gain can be set and Q is fixed. The automatic adjustment in that case can be
performed, for example, as follows. That is, the measured frequency characteristic is compared
with a predetermined target gain, and the peak frequency at a location exceeding the target gain
on the frequency characteristic and the difference between the gain and the target gain at the
peak frequency are detected, respectively. The center frequency and gain of the front equalizer
are set to match the detected peak frequency and gain difference.
[0016]
According to the automatic adjustment using these parametric equalizers, since the parametric
equalizer can be constituted by, for example, an IIR filter, the amount of calculation can be easily
adjusted with a small amount of calculation, and even for peaks of frequency characteristics
distributed in a wide band. It can respond flexibly. Further, since the adjustment is made in
advance prior to actual use, howling can be prevented in advance.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be
described below. FIG. 5 shows an example of the sound field control unit of the present invention.
Further, the disassembled state is shown in FIG. As shown in FIG. 6, the sound field control unit
62 has a frame 66 erected on a base (base) 64. The circuit unit 68 and the amplifier unit 70 are
attached to the frame 66. The amplifier unit 70 can use, for example, about 200 Wmax. Further,
a speaker system 72 is attached to the upper end portion of the frame 66 with the radiation
direction of the sound directed upward. A speaker grill 74 is attached to the radiation surface of
the speaker system 72. A microphone holder 76 is provided on the base 64, and a microphone
unit 78 is attached to the microphone holder 76. As the microphone unit 78, for example, a nondirectional electret type (condesan microphone) is used. The mounting position of the
microphone unit 78 is not limited to the lower position of the sound field control unit 62, and
may be another position as long as the sound field can be received flat.
[0018]
At the front and back of the frame 66, a front cover 80 and a rear cover 82 constituting a
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housing are attached. Side covers 84 and 86 are attached to the left and right sides of both
covers 80 and 82, respectively. The front cover 80 is provided with a microphone sound
receiving port 88 near the lower end portion, and an infrared light receiving window 90 in which
an infrared light receiving element is disposed and a power display LED 92 are provided at the
upper portion. On top of the rear cover 82, a fall prevention wire mounting eyebolt 94 is
attached. As shown in FIG. 5, the front cover 80, the rear cover 82, and the side covers 84 and 86
constitute a cylindrical casing 94 having a substantially elliptical cross section.
[0019]
The sound field control unit 62 is installed upright on the floor at a height of about 1.5 to 2.0 m.
The base 64 can also be screwed to the floor if desired. The reproduction sound of the speaker
system 72 is emitted upward from the upper end opening 96 of the housing 94. The microphone
unit 78 is disposed on the side of the housing 94 on the side of the front panel 80 and picks up
the sound around the sound field control unit 62. The infrared receiving window 90 receives an
infrared command signal transmitted from the infrared remote control transmitter. The power
display LED 92 lights up when the sound field control unit 62 is powered on. The microphone
unit 78, the speaker system 72, and the power display LED 92 are connected to the circuit unit
68 inside the housing 94 via a signal line (not shown).
[0020]
At the lower part of the rear cover 82, a rear panel 98 shown in FIG. 7 is disposed. On the rear
panel 98, a male connector 100 is disposed as a forward direction output connector (reverse
direction input connector), and a female connector 102 is disposed as a forward direction input
connector (reverse direction output connector). . The forward signal input from the connector
102 is taken in and used by the circuit unit 68 and output from the connector 100. Further, the
signal in the reverse direction (return) input from the connector 100 is taken in and used by the
circuit unit 68, and is output from the connector 102. Further, the rear cover 82 is provided with
a main power switch 104. The power of the sound field control unit 62 is supplied from a power
cord 105. The connectors 100 and 102 are connected to the circuit unit 68 inside the housing
94 via signal lines (not shown). A transmission cable is connected to the connectors 100 and 102
from the outside.
[0021]
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7
An example of arrangement of the sound field control unit 62 in a room is shown in FIG. The
room 106 has an area of about 20 to 120 square meters, and four sound field control units 62-1
to 62-4 are disposed at the four corners. The respective sound field control units 62-1, 62-2, 623, 62-4 (referred to as units A, B, C, D, respectively) are all the same, and are configured as shown
in FIGS. There is. The units A to D are connected to one another by connecting the units A to B,
the units B to C, and the units C to D in series by three composite cables (transmission cables)
108, and the whole is integrated. The sound field control unit 160 is configured.
[0022]
The connection structure of units A to D is schematically shown in FIG. The composite cable 108
has a female connector 114 attached to one end and a male connector 116 attached to the other
end. The connector 114 is connected to the connector 100 of the sound field control unit 62, and
the connector 116 is connected to the connector 102 of another sound field control unit 62.
[0023]
The sound pickup signals and control signals (command signals) of the respective units A to D
are transmitted to the composite cable 108. The collected sound signal is transmitted, for
example, in the same manner as in the AES / EBU format, and two channels (two units) of signals
are allocated in time division to a pair of signal lines (two + and-) in the composite cable 108 And
transmitted in 2 channels-serial-24 bits. Also, the composite cable 108 is provided with signal
lines in the forward and reverse directions for the same channel. Therefore, the four collected
signals collected by each of the units A to D are transmitted using a total of eight signal lines in
the composite cable 108. The composite cable 108 additionally has four signal lines, and the
composite cable 108 is configured by a total of 12 signal lines. The assignment of signals to 12
signal lines is shown below.
[0024]
Signal line Signal type Direction Polarity Pickup unit 1 Pickup signal order + A + B 2 Pickup
signal order-A + B 3 Pickup signal order + C + D 4 Pickup signal order-C + D 5 Pickup signal
Reverse + A + B 6 Pickup signal Reverse-A + B 7 Pickup signal reverse + C + D 8 Pickup signal
reverse-C + D 9 control signal + 10 control signal-11 word clock 12 ground According to this,
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forward direction (A → by means of three composite cables 108 connecting units A to D in FIG.
The B → C → D) transmission path and the transmission path in the reverse direction (D → C →
B → A) are configured, and the collected signals and control signals of all the units A to D in any
of the three composite cables 108 Is being transmitted. For example, the sound pickup signal of
unit B is transmitted to units C and D through signal lines 1 and 2 (ie, the A + B line in the
forward direction), and is folded at unit D, and signal lines 5 and 6 (ie, the reverse direction). Is
transmitted to unit A through the (A + B) line of
[0025]
Each CPU provided in each of the units A to D has a function of automatically judging which of
the units A to D is. This determination is made as follows. That is, when the units A to D are
connected by the three composite cables 108, two units in which the composite cable 108 is not
connected to the male connector 100 or the female connector 102 are generated. First, a unit not
connected to any female connector 102 recognizes its own unit as a unit A as a start point, and
sends out the numerical value 1 to the adjacent unit through the control signal line. A unit
receiving the value 1 recognizes it as a unit B, adds 1 to the value 1 and sends the value 2 to the
adjacent unit. A unit receiving the value 2 recognizes it as a unit C, adds 1 to the value 2 and
sends the value 3 to the adjacent unit. The unit receiving the value 3 is recognized as the unit D,
and since nothing is connected to the male connector 100, it is also recognized as the end point,
1 is added to the value 3 and the value 4 is sent back to the channel A unit. . The channel A
knows that the total number of units is 4 by the return of the number 4.
[0026]
In this way, the position of each unit A to D is automatically recognized by itself, and the
transmission direction of the sound pickup signal of the own unit is determined accordingly. That
is, in the case of the units A to C, the sound collection signal of the own unit is sent in the
forward direction (turned back by the unit D), and in the case of the unit D, the sound collection
signal of the own unit is sent in the reverse direction. As a result, the sound collection signals of
all the units A to D are transmitted to all of the three composite cables 108 connecting the units
A to D. Further, the CPU of the unit A manages the whole and issues commands (for example,
commands for executing automatic adjustment in the order of A, B, C, D) to the other units B to D.
In addition, unit A becomes a clock master, and the master clock generated in unit A is supplied
to the word clock line in composite cable 108, and all units B to D share this clock, thereby
achieving all units. Synchronized with A to D. The remote control signal received by the infrared
receiving window 90 of any of the units A to D is taken into the unit and transmitted to all other
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units through the control signal line in the composite cable 108. By this, even if the remote
control signal is received by any unit, it is transmitted to all the units.
[0027]
Transmission of control signals among the units A to D will be described. The control signal line
consists of two lines, HOT (+) and COLD (-), and both lines are (+) when not in use (when no
control signal is sent from any unit) , And only when in use (+) and (-) (this in-use state is
hereinafter referred to as BUZY). This makes it possible to determine whether the control signal
line is in use. All control signals are sent as a group of data called "packet". The unit to be
transmitted first checks the state of the control signal line. If it is BUZY, the control signal line is
in use, so wait until it's empty. When the control signal line becomes free, it is put into the state
of BUZY by itself to acquire the right of transmission and start transmission. When the control
signal line becomes BUZY due to reasons other than one's own, another unit is trying to transmit,
so it enters a receiving operation.
[0028]
The circuit configuration in the sound field control unit 62 is shown in FIG. The portion encircled
by an alternate long and short dash line 170 in FIG. 1 can be configured by a DSP (digital signal
processor). The collected sound signal collected by the microphone unit 78 is converted to a
digital signal by the A / D converter 112 through the head amplifier 110, and the collected sound
signal is switched through the subtractor 114, the attenuator 116, and the programmable
equalizer 124. It is input to the circuit 132. Also, the sound pickup signals of the other units
inputted through the input / output circuit 122 are inputted to the sound pickup signal switching
circuit 132 through the attenuators 118, 120, 122 and the programmable equalizers 126, 128,
130. The sound pickup signal switching circuit 132 sequentially switches these four sound
pickup signals and outputs them to the subsequent stage circuit.
[0029]
An example of the switching of the sound collection signal in the sound collection signal
switching circuit 132 of each of the units A to D is shown in FIG. According to this, since the
collected sound signals to be reproduced in the respective units A to D are sequentially switched,
the transmission frequency characteristics are averaged by the spatial averaging effect, the
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coloration is reduced and the howling margin is expanded. The switching cycle can be set to, for
example, about 1 to 1/2 of the reverberation time in the room.
[0030]
The attenuators 118, 120 and 122 and the programmable equalizers 126, 128 and 130 have
transmission characteristics and gain when the sound collection signal switching circuit 132
selectively outputs the sound collection signal of another unit (when looping with other units).
When different from the transmission characteristics or gain when selecting and outputting the
sound pickup signal of the own unit (during the self loop), the frequency characteristic of the
loop with another unit or the frequency characteristic or gain based on the frequency
characteristic or gain of the own loop It is for adjusting the gain. As a result, it is possible to
compensate for various differences in arrangement among the units, and to cope with use under
special conditions, for example, where vertically elongated rooms or units are arranged in an
invisible position. it can. Since the frequency characteristic and gain of its own loop are adjusted
by programmable equalizer 140 and attenuator 142 as will be described later, attenuator 116
for its own loop may normally remain at gain 1, and programmable equalizer 124 The
characteristic may be flat with a gain of 1.
[0031]
The sound pickup signal of the own unit and the sound pickup signals of the other units
transmitted from the previous unit are transmitted to the next unit through the input / output
circuit 122.
[0032]
The collected sound signal output from the collected sound signal switching circuit 132 has its
frequency characteristic corrected by the programmable equalizer 134 (closed loop frequency
characteristic correction), an initial reflected sound is generated by the FIR filter 138, and the
frequency is further measured by the programmable equalizer 140. The characteristics are
corrected (the open loop frequency characteristic correction for its own loop), and the attenuator
142 adjusts the open loop gain for its own loop.
The parameters of the FIR filter 138 are varied continuously and randomly on the time axis, as
shown in FIG. As a result, the frequency characteristics of the FIR filter 138 are averaged to
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further reduce the coloration and expand the howling margin. The fluctuation of the time axis of
the parameter is realized by moving the output taps of the FIR filter 138 in an uncorrelated
manner with a fluctuation width of, for example, 0.25 msec to 5 msec. The output of the
attenuator 142 is reproduced by the speaker system 72 through the volume 172, the muting
circuit 144, and the amplifier unit 70.
[0033]
The howling canceller 148 prevents the generation of howling due to the fact that the
reproduction sound of the collected sound signal of its own unit is fed back directly to its own
microphone, and this is the timing at which the collected sound signal of its own unit is
reproduced. The collected signal is fed back to the subtractor 114 to cancel the signal directly
fed back from the speaker system 72 of its own to the microphone unit 78 of its own.
[0034]
The infrared remote control transmitter 150 performs command operations such as power on /
off commands for all units A to D, a reverberation pattern switching command, and an
adjustment mode start command.
When a reverberation pattern switching command (selection command) is issued, the reflected
sound parameter of the corresponding reverberation pattern is read out from the ROM 152 in
the sound field control unit 62, and is set in the FIR filter 138 to switch the reverberation
pattern. .
[0035]
The adjustment mode of the loop characteristic performed at the beginning of installation of the
sound field control unit 62 in the room will be described. When the adjustment mode is started
by a command from the infrared remote control transmitter 150, the adjustment operation is
executed fully automatically under the control of the CPU 158 of the unit A. The progress of the
adjustment operation is managed by the CPU 158 in the unit A, which is the core of the entire
system. The procedure of the automatic adjustment operation is shown in FIG. When the
adjustment start is instructed (S1), the adjustment in the open loop state is first started. That is,
the switching operation of the sound collection signal switching circuit 132 of FIG. 1 is stopped,
and only its own loop is used (that is, the sound collection signal of its own unit is continuously
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output from the sound collection signal switching circuit 132). ). Then, for example, the signal
path between the attenuator 142 and the volume 172 (or between the programmable equalizer
140 and the attenuator 142 or between the FIR filter 138 and the programmable equalizer 140)
of FIG. It becomes a loop state. In this state, a reference signal for measurement such as pink
noise and white noise is generated from the reference signal generation circuit 154, and this is
input from the volume 172 (or the attenuator 142 or the programmable equalizer 140) and
reproduced by the speaker system 72. The reproduced sound is fed back to the microphone unit
78 and collected. The signal passes through the attenuator 116 of the own loop and the
programmable equalizer 124, passes through the sound pickup signal switching circuit 132 and
the programmable equalizer 134, and is reflected by the FIR filter 138. A signal is generated. By
measuring the frequency characteristic and gain of a signal obtained through the programmable
equalizer 140 and the attenuator 142 (or the output of the programmable equalizer 140 or the
output of the FIR filter 138) of the reverberation signal with the measurement circuit 156, the
remarkable peak can be reduced. The CPU in its own unit automatically adjusts the
programmable equalizer 140 to flatten the frequency characteristics (S2). The fine peak and dip
on the frequency characteristic can be eliminated by averaging by the sound pickup signal
switching operation, so the frequency raised as an envelope of the frequency characteristic is
reduced. This operation is sequentially performed on all combinations of units A to D and the
reverberation pattern.
[0036]
Once the frequency characteristics of its own loop have been flattened for all units A to D, the
transmission characteristics and the transmission characteristics can be obtained using the
measurement reference signal in a state where the collected sound signal from other units is
selected (loop state with other units). Attenuator 118, 120, 122 and programmable equalizer so
that the gain can be measured and the frequency characteristic and gain of the desired
characteristic (for example, the same characteristic as the own loop) can be obtained with
reference to the frequency characteristic and gain of the own loop Adjust 126, 128, 130 (S3).
The adjustment procedure first switches, for example, the sound pickup signal switching circuit
132 for the unit A sequentially to form a loop with the units B, C, D, and the attenuators 118,
120, 122 of the unit A and the programmable equalizers 126, 128, 130 And when it is finished,
form a loop with other units in units B, C, D as well, and adjust the attenuators 118, 120, 122
and the programmable equalizers 126, 128, 130, respectively. The adjustment of step S3 can be
omitted.
[0037]
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When this adjustment is completed, it is fixed to its own loop again to adjust its own open loop
gain. That is, although the frequency characteristic of its own loop should be almost flat by the
adjustment of the step S2, the characteristic may be generated in the case of the equalizer using
the IIR filter. That is, although the IIR type equalizer is inexpensive, it has a drawback that the
phase characteristic goes wild. And when many IIR type equalizers are used, it may also affect the
amplitude characteristics and unintended sharp peaks may occur in the frequency
characteristics, and the loop is closed if the open loop gain is 0 dB or more. Oscillation (howling).
Therefore, the measurement reference signal is generated again and the frequency characteristic
is measured by the measurement circuit 156, and the peak value in the frequency characteristic
is on the same level as the howling level (a level at which the howling easily occurs if it becomes
larger The attenuator 142 is automatically adjusted to set the loop gain to 0 dB or less (e.g., -12
dB) (S4). This operation is sequentially performed on all combinations of reverberation patterns
of units A to D.
[0038]
With the above, the adjustment of the open loop state is completed, and the adjustment in the
closed loop state is performed this time (S5). That is, while the loop is closed and the switching
operation of the sound pickup signal switching circuit 132 is performed, the measurement
reference signal is put in the loop and reproduced from the speaker 72, and the frequency
characteristic of the feedback signal (sound pickup signal) is measured. The circuit 156 measures
it. Then, the programmable equalizer 134 is adjusted so that the gain of the frequency
characteristic does not exceed 0 dB. This operation is sequentially performed for all
combinations of units A to D and each reverberation pattern. Thus, the adjustment operation
ends (S6).
[0039]
The adjustment amounts of the programmable equalizer 124, 126, 128, 130, 134, 140 and the
attenuators 116, 118, 120, 122, 142 adjusted by the above automatic adjustment operation are
stored in a memory (not shown) in the own unit. The corresponding adjustment amount is read
in synchronization with the reverberation pattern selection operation, and the programmable
equalizers 124, 126, 128, 130, 134, 140 and the attenuators 116, 118, 120, 122, 142 are
automatically adjusted. . This further reduces the coloration and further expands the howling
margin.
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[0040]
Here, an automatic adjustment method when the programmable equalizer 140 is configured by a
parametric equalizer will be described. FIG. 13 shows the configuration of the portion from the
equalizer 140 to the volume 172 of FIG. 1 at the time of adjustment. The parametric equalizer
140 can set the center frequency, gain, and Q. The switch SW1 and the adder 174 are disposed
between the attenuator 142 and the volume 172. The reference signal generation circuit 154 is
formed of, for example, a pink noise generator. The pink noise generated here is added at the
addition point 174 via the switch SW2. The measurement circuit 156 is configured of, for
example, an FFT analyzer. The on / off switching of the switches SW1 and SW2 at the time of
automatic adjustment and other necessary operations are automatically performed by a
command from the CPU 158.
[0041]
A procedure for automatically adjusting the characteristics of the parametric equalizer 140 will
be described with reference to FIG. (1) FFT Measurement (S11) When automatic adjustment is
commanded, the characteristic of the parametric equalizer 140 is flattened (the characteristics of
the other equalizers PEQ1 and PEQ2 of FIG. 1 are also flattened). Further, the gain of the
attenuator 142 is set to 0 dB, and the volume 172 is maximized. Also, the switch SW1 is turned
off to shut off the loop, and the switch SW2 is turned on to supply pink noise from the pink noise
generator 154 into the path. The pink noise is reproduced by the speaker system 72 and
collected by the microphone unit 78 through the indoor space. The collected signal is measured
for frequency characteristics by the FFT analyzer 156.
[0042]
(2) Smoothing process (S12) The calculation result by the FFT analyzer 156 is, for example, as
shown in FIG. 15A. However, in order to make the process by the CPU 158 easy, smoothing is
performed as shown in FIG. Smoothing is performed, for example, by averaging ± 10 points of
FFT data. However, since the data of the FFT has a linear frequency width, it does not take an
average in the low band (100 Hz or less) when viewed on the logarithmic axis, and gradually
increases the number of points to be averaged in the middle band (100 Hz to 1 kHz). In the range
(1 kHz or more), smoothing is performed by averaging ± 10 points.
10-04-2019
15
[0043]
In addition, averaging ± 10 points means taking the average of ± 10 data before and after all
data of FFT. For example, let f (x) be the original data of FFT, and F (x) be the data after
averaging:
[0044]
Then, if this x is performed on all the FFT data f (x), the same number of FFT average data F (x) as
the original data f (x) is calculated.
[0045]
(3) Equalization target level setting (S13) The average value of, for example, the midrange (500
Hz to 2 kHz) of the original data of the FFT is taken and used as the equalizing target level.
In the example of FIG. 15 (b), -1.5 dB is set as the target level. The reason why the average value
of 500 Hz to 2 kHz is taken is that the band is empirically insusceptible to the characteristics of
the room.
[0046]
(4) Peak detection and characteristic setting (S14-16) Find the peak position on the smoothed
frequency characteristic (the top of the highest level of the peaks among a plurality of peaks in
the entire frequency characteristic). For example, if it is assumed that the target level is exceeded
in a certain portion of the frequency characteristic as shown in FIG. 16A, the frequencies f1 and
f2 at the intersection of the frequency f0 at the peak position and the target levels on both sides
thereof are detected. Then, R1 = f1 / f0R2 = f0 / f2 is calculated as the ratio between the
frequency f0 at the peak position and the frequencies f1 and f2 at the intersection of the target
level, and the larger one is adopted.
[0047]
10-04-2019
16
The reason for adopting the one with the larger frequency ratio is as follows. That is, in the case
where there is a characteristic as shown in FIG. 16 (a), as shown in FIG. 16 (b), the characteristic
of the equalizer matched to each of the frequencies f1 and f2 can be considered. In this case, the
equalizer characteristic EQ1 matched to the smaller frequency ratio f1 becomes a broad (dull)
characteristic, and as a result, the necessary band is removed. Therefore, the sharp equalizer
characteristic EQ2 is set in accordance with f2 having a large frequency ratio so as not to cut too
much as necessary. However, in this case, since the uncut portion appears on the contrary, the
simulation calculation of step S17 described later is performed, and the equalizer characteristic
setting is performed.
[0048]
Subsequently, the difference GdB between the target level and the level at the peak position is
determined. Then, from the frequency ratio R1 or R2 thus obtained and the level difference GdB,
a Q necessary for making this peak equal to or less than the target level is obtained. For this
purpose, for example, the frequency ratio for each combination of level differences G and Q as
shown in Table 1 is prepared as a table and prepared in advance in a memory (not shown). Then
(if the corresponding level difference is not in the table, the closest level difference), select Q that
provides the frequency ratio closest to the determined frequency ratio.
[0049]
When the frequency f0 at the peak position and the level difference GdB and Q are obtained as
described above, the characteristic of one band of the parametric equalizer 140 is set to the
center frequency f0, the gain G and the selectivity Q using these values.
[0050]
The above setting procedure will be described using the example of FIG. 15 (b). The frequency f0
of the peak position is 280 Hz, the frequencies of the intersections with the target levels on both
sides are f1 = 180 Hz, f2 = 360 Hz, and the frequency ratio is R1 = 180/280 = 0.6429 R2 =
280/360 = 0.7787 and the larger R2 = 0.7778 is adopted.
On the other hand, the difference between the target level and the peak position is G = -7.0 dB,
and from Table 1, the value of Q at which the frequency ratio closest to the frequency ratio
10-04-2019
17
0.7778 is obtained under the level difference -7.0 dB. Adopt 5.0 as. Then, as described above, as
the characteristics of the parametric equalizer 140, the center frequency is set to 280 Hz, the
gain to -7.0 dB, and Q to 5.0.
[0051]
(5) Simulation (S17) The CPU 158 simulates the frequency characteristics as a result of
equalizing the measured frequency characteristics with the parametric equalizer 140 having the
characteristics set as described above. That is, the frequency characteristic of the parametric
equalizer 140 is converted into data in the CPU 158, and is subtracted from the smoothed FFT
data (FIG. 15 (b)) to predict the frequency characteristic after equalization. Then, if a peak
exceeding the target level still exists in the frequency characteristic, the peak is calculated in the
same procedure (S14 to S17) as described above to set the characteristic of another band of the
parametric equalizer 140, If no peak exceeding the target level finally exists by repeating the
setting, the setting is completed (S18). The result of equalizing the characteristics of FIG. 15 (a)
using the parametric equalizer 140 whose setting has been completed is shown in FIG. 15 (c).
According to FIG. 15C, any part of the frequency characteristic is −1.5 dB or less set as the
target level, and the occurrence of howling can be prevented in advance.
[0052]
The programmable equalizer 134 (PEQ2) of FIG. 1 is also configured by a parametric equalizer,
and FFT measurement can be separately performed by the same method as that of FIG. 14 to set
characteristics based on the result. When setting the parametric equalizer 134, the switch SW1
in FIG. 13 is turned on to close the loop, and the parametric equalizer 140 is set to the above
setting state, and the other programmable equalizers 124 to 130 (PEQ1) are flat. When the
setting of the parametric equalizer 140 (PEQ3) is finished, almost flat frequency characteristics
should have been obtained, but a whisker-like peak remains. A parametric equalizer 134 is used
to remove the whisker-like peaks one by one. Here, it is only necessary to remove the peak-like
whiskers, and Q of the parametric equalizer 134 is fixed at a fixed sharp value (about 10.0) so as
not to be removed to the other part, the center frequency f0 and the gain G Is set based on the
FFT measurement result.
[0053]
10-04-2019
18
In addition, the programmable equalizers 124 to 130 (PEQ1) of FIG. 1 can also be configured by
parametric equalizers, and FFT measurement can be individually performed by the same method
as that of FIG. 14 to set characteristics individually based on the results. . As described above,
when the automatic adjustment of the characteristics of all the equalizers PEQ1, PEQ2 and PEQ3
is completed, the volume can be adjusted to a desired volume and used in practice.
[0054]
Although the number of speaker systems in one sound field control unit 62 is one in the above
embodiment, a plurality of sound system may be provided. An example is shown in FIG. In the
sound field control unit 156, the woofer 160 is disposed downward at the lower end portion of
the housing 158, and the squawker 162 is disposed upward at the upper end portion. The sound
reproduced from woofer 160 is emitted to the outside from an opening 164 formed in the lower
part of housing 158. By providing a plurality of speaker units in this manner, an effect of
diffusing the sound more can be obtained.
[0055]
As described above, according to the present invention, the introduction of the sound field
support system is facilitated.
[0056]
Brief description of the drawings
[0057]
1 is a block diagram showing an embodiment of a sound field control unit of the present
invention, and is an internal circuit diagram of the sound field control unit of FIG. 5;
[0058]
Fig. 2 shows the principle of acoustic feedback.
[0059]
FIG. 3 is a layout view showing an example of conventional introduction of acoustic feedback.
10-04-2019
19
[0060]
4 is a block diagram showing a circuit configuration of the system of FIG.
[0061]
FIG. 5 is an external view showing an embodiment of a sound field control unit of the present
invention.
[0062]
6 is an exploded view of the sound field control unit of FIG. 5;
[0063]
FIG. 7 is a view showing a rear panel disposed on the back side of the sound field control unit of
FIG. 5;
[0064]
FIG. 8 is a view showing an embodiment of a sound field control device of the present invention,
and is a layout view showing an example of introduction of the sound field control unit of FIG. 5;
[0065]
9 is a schematic view showing a connection structure of the composite cable 108 of FIG.
[0066]
FIG. 10 is a diagram showing an operation example of the sound pickup signal switching circuit
of FIG. 1;
[0067]
FIG. 11 is a schematic view showing time axis fluctuation operation of the FIR filter of FIG. 1;
[0068]
12 is a flowchart of an automatic adjustment operation by the sound field control unit of FIG.
[0069]
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20
13 is a block diagram showing a configuration when the characteristic of the parametric
equalizer 140 is automatically set when the programmable equalizer 140 of FIG. 1 is configured
by a parametric equalizer. FIG.
[0070]
14 is a flowchart showing an automatic setting procedure of the characteristic of the parametric
equalizer 140 according to the configuration of FIG. 13. FIG.
[0071]
15 is a frequency characteristic diagram showing a specific example of the characteristic setting
operation according to the procedure of FIG.
[0072]
FIG. 17 is a partially enlarged view of frequency characteristics for explaining the procedure of
steps S15 to S16 of FIG. 14;
[0073]
FIG. 17 is an external view showing another embodiment of a sound field control unit according
to the present invention.
[0074]
Explanation of sign
[0075]
62 Sound Field Control Unit 68 Circuit Unit (Electric Circuit) 70 Amplifier Unit (Amplifier, Electric
Circuit) 72 Speaker System (Speaker) 78 Microphone Unit (Microphone) 80 Front Cover (Side
Side of the Case) 90 Infrared Reception Window (Infrared light receiving unit) 94 Case 96 Upper
opening 100, 102 terminal (sound collection signal input / output terminal) 108 composite cable
(transmission cable) 132 sound collection signal switching circuit (sound collection signal
switching means) 134 equalizer (front side) 138 FIR filter 140 Equalizer (rear side) 142
Attenuator 150 Infrared remote control transmitter 154 Reference signal generation circuit
(reference signal generation means) 156 Measurement circuit (measurement means) 158 CPU
160 Sound field control device
10-04-2019
21
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