JP2001095084A - Multi-channel acoustical coupling gain reducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably suppress howling in a multi-channel acoustic system. SOLUTION: An acoustical coupling quantity between each loudspeaker and microphone is measured from each of input of loudspeakers 11 to 1M of a reproducing channel and each of output of the microphones 21 to 2N of a sound pick-up channel. The ratio of each of the outputs of the microphones 21 to 2N to an output obtained by subtracting its echo simulation signal from the output is obtained. Then, a coupling gain of loudspeaker input and echo canceling output are obtained by a measuring means 17 from the ratio and the acoustical coupling quantity. The priority of an input reproducing signal from a reproducing channel and the sound pick-up signal priority of the echo canceling output are judged by a priority deciding means 18. The respective loss quantities of the variable loss device 51 to 5M of each reproducing channel and the variable loss devices 61 to 6N of each sound pick-up channel are obtained by a control means 19 from the deciding result and the coupling gain and they are set respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication system having at least two loudspeakers for reproducing at least two reproduction signals, respectively, and a multi-channel sound reproduction system for obtaining a pickup signal as an output of at least one microphone. The present invention relates to a multi-channel acoustic coupling gain reduction device that prevents howling and echo from occurring.

[0002]

2. Description of the Related Art In a communication conference system or the like, as shown in FIG. 6, acoustic coupling between speakers 1A and 1B and microphones 2A and 2B installed at communication points A and B, respectively.
When the gain of the closed loop CL formed by the communication lines L1 and L2 exceeds 0 dB, howling occurs,
It interferes with the call with the other party. As a device for solving this problem when both the reproduction channel and the sound pickup channel are one, Y. Haneda, S. Makino, J. Kojima,
and S. Shimauchi, “Implementation and evaluation of
an acoustic echo canceller using duo-filter contr
ol system, ”Proc. EUSIPCO96, vol.2, pp.1115-1118 (1
996). As described above, there is a one-channel acoustic coupling gain reduction device 10 shown in FIG. At each communication point,
A simulated signal of an echo circulating from the speaker 1 to the microphone 2 is generated by the simulated signal generator 3, and an echo canceller 4
By subtracting the simulation signal from the output signal of the microphone 2, the acoustic coupling between the speaker 1 and the microphone 2 is reduced. Further, the communication partner based on the coupling gain measured from the input terminal of the speaker 1 to the output terminal of the echo canceller 4 measured by the coupling gain measuring means 7 and whether the transmitting side or the receiving side in the communication conference is speaking. (A communication line) or a reproduced sound signal priority judging means 8 for judging the priority of a reproduced signal supplied from a reproduced signal source and a sound signal output from each microphone 2 and passed through the echo canceller 4. There is a loss amount control means 9 for determining the loss amount of the reproducing-side variable loss device 5 and the sound-collecting-side variable loss device 6 based on the priority determination result, which can also reduce acoustic coupling.

In this device, when a simulated echo signal is correctly generated, the loss of both the reproducing-side variable loss device 5 and the sound-collecting-side variable loss device 6 can be reduced, and the echo signal can be reduced from the output signal of the microphone 2. Only the voice of the person speaking from the near end of the microphone 2 can be transmitted to the other party as it is, and no intermittent sensation is generated even if two directions are simultaneously uttered. Conversely, when the echo simulated signal is not correctly generated, the acoustic coupling between the speaker 1 and the microphone 2 has not been reduced, but either the reproduction-side variable loss device 5 or the sound collection-side variable loss device 6 has not been reduced. Is selected in accordance with the call state, and the gain of the acoustic coupling is reduced by increasing the loss of the selected loss device. If the loss amount of either the reproduction-side variable loss device 5 or the sound-collection-side variable loss device 6 is large, an intermittent feeling occurs during two-way simultaneous communication, but usually the accuracy of the echo simulation signal is adaptive. After that, the reproducing-side variable loss device 5 and the sound-collecting-side variable loss device 6
It is no longer necessary to increase the amount of each loss. in this way,
It is an advantage of this apparatus that the gain by acoustic coupling is constantly reduced by any one of the echo canceller 4 or the reproducing-side variable loss unit 5 and the sound-collecting-side variable loss unit 6, and a stable acoustic system that does not generate howling is constructed. It is.

In a communication conference system, at one point, a signal from a reproduction signal source (communication line) of M channels (M > 2) is reproduced by M speakers, and N signals (N > ) are reproduced.
The collected sound signal of the microphone of 1) may be output to a collected sound signal storage destination (communication line). In this case, as a method for correctly evaluating the acoustic coupling between the M speakers and the N microphones which causes howling, the present inventors have proposed Japanese Patent Application Laid-Open No. 10-257585 “Multi-channel acoustic coupling evaluation method”. . In this evaluation method, the m (= 1, 2,..., M) th speaker and n (=) of a multi-channel sound system in which the number of speakers is M and the number of microphones is N
The frequency characteristic of the transfer function between the (1, 2,..., N) th microphone is G _mn (exp (jω)), and the acoustic system frequency characteristic matrix having these frequency characteristics as elements is given. And ^T represents the transpose of the matrix. G (ex) in equation (1)
p (jω)), the frequency characteristic of the input signal to the m-th (= 1, 2,..., M) -th speaker is represented by X _m (exp (j
ω)), and the input signal frequency characteristic vector obtained by combining the Then, for each frequency,

[0005]

(Equation 1)

G (exp (j
states that the norm of ω)) corresponds to the acoustic coupling of a multi-channel acoustic system.

[0007]

SUMMARY OF THE INVENTION The present invention
In a multi-channel sound system including at least one reproduction channel and at least one sound collection channel,
The present invention relates to an apparatus having a howling suppression function as described above. That is, the problem to be solved by the present invention is to extend the function of the one-channel acoustic coupling gain reduction device described in the related art to a multi-channel audio system, and realize stable howling suppression in the multi-channel audio system. That is. In particular, the loss amounts of the variable loss device on the reproduction side and the variable loss device on the sound collection side to be introduced at this time are:
The main task is to propose a means for providing a minimum amount of howling that does not occur.

[0008]

According to the present invention, speed is improved.
In addition to the transfer function between microphone and microphone, as shown in FIG.
In addition, the loss amount of the reproducing-side variable loss device (multiplication
Expressed as a coefficient) LR ₁, LR_Two, ..., LR_MAnd each income
The loss amount of the variable loss device on the sound collection side of the sound channel (
Express) LT₁, LT_Two, ..., LT_NAnd the echo canceller
Echo cancellation amount E₁(Exp (jω)), E_Two(E
xp (jω)), ..., E_N(Exp (jω))
Evaluate the stability of the system. In other words, the sound at this time
Frequency characteristic matrix M (exp (jω)) of the entire system
Is

[0009]

(Equation 2)

## EQU1 ## The matrix M (exp (j
ω)), the stability can be evaluated by the norm {M (exp (jω))}, and {M (exp (jω))} <1 for all frequencies. reproducing side loss factor of the variable loss circuit _{LR 1, LR 2, ...,} LR M and loss factor LT _1, LT ₂ of the sound collection side variable loss circuit of each sound collecting channel, ..., L
Determine T _N. Action To determine the loss amount of the variable loss device on the reproduction side of each reproduction channel and the loss amount of the variable loss device on the sound collection side of each sound collection channel based on the stability conditions of the multi-channel acoustic system, the minimum necessary for preventing howling Loss can be given.

[0011]

FIG. 2 shows a configuration of a multi-channel acoustic coupling gain reduction apparatus 20 embodying the present invention. 7, the components having the same functions as those in FIG. 7 have the same names as those in FIG. 7, but those having different realization means, such as being expanded for multiple channels. , Different giving numbers.

[0012] 1 as in the case of the channel, the speaker ₁ 1 M channels, 1 _2, ..., microphone 2 ₁ of the N-channel from 1 _{M, 2} 2, ..., simulation signal generating echo simulation signal of sneaking into 2 _N Generated by the device 13. The generation of the simulated signal is described in, for example, Japanese Patent Application No. 7-50002, "Echo Cancellation Method for Multi-Channel Audio Communication Conference". By subtracting the corresponding simulated signal from each output signal of the microphones 2 ₁ , 2 ₂ ,..., 2 _N by the echo canceller 14,
Speakers 1 ₁ , 1 ₂ ,..., 1 _M and microphones 2 ₁ , 2
Reduce acoustic coupling between ₂ , ..., _2N . Further, the speakers 1 ₁ ,
1 _2, ..., 1 each of the coupling gain from the input terminal of _M to the output terminals of the echo canceller 14, and a reproduction signal source output from the reproduced signal and the microphone is supplied from (the communication line) echo cancellers Based on the result of the priority determination by the reproduced sound collection signal priority determination means 18 for determining the priority with the collected sound signal after passing, the reproduction-side variable loss devices 5 ₁ , 5 ₂ ,
, 5 _M , and loss amount control means 19 for determining the respective loss amounts of the sound-collecting-side variable loss devices 6 ₁ , 6 ₂ ,..., 6 _N. This also reduces the gain due to acoustic coupling. Play side variable loss device 5 _1, 5 _2, ..., 5 _M each reproduced signal source and the loudspeaker ₁ 1, 1 _2, ..., is inserted between the 1 _M, the sound collection side variable loss circuit 6 _and 62, .., 6 _N are inserted between each output of each echo canceller 14 and each sound pickup signal storage destination.

In this configuration, what is important is the amount of loss.
The control means 19 controls the reproduction-side variable loss device 5₁, 5_Two, ..., 5
_M, Sound pickup side variable loss device 6₁, 6_Two, ..., 6_NFor
How much minimum loss to avoid howling
In the following, two channel re-
This will be described using a system having a live / sound pickup system as an example.2 channel example ・ Coupling gain measuring means Each speaker 1₁, 1_TwoAcoustic echo canceller 1 from the input end of
In measuring the coupling gain to each output end of
Pea 1₁, 1_TwoMicrophone 2 from the input end of₁, 2
_TwoAll speakers 1 up to the output end of₁, 1_TwoAnd microphone
Lohon 2₁, 2 _TwoAcoustic coupling amount for each combination (section
Multi-channel system described in Means to Solve the Problem
Is different from the acoustic coupling amount of the body) and each microphone 2₁,
2_TwoFrom the output terminal of the acoustic echo canceller 14 to the output terminal
, Ie, the amount of echo cancellation.
That is, the coupling gain measuring means 17 and the acoustic coupling amount measuring means
It consists of co-erasing amount measuring means.

As shown in FIG. 3, the acoustic coupling amount
Speaker 1₁, 1_TwoAnd two microphones 2₁, 2
_TwoAre symmetrically installed (many applications
This assumption is valid.)
Between the microphone and the microphone (1₁And 2₁Between 1,_TwoAnd 2_Two
A), the acoustic coupling amount is A, and the speaker is
Between microphone and (1₁And 2_TwoBetween 1,_TwoAnd 2₁Among
Let B be the amount of acoustic coupling. A and B are speakers
1₁, 1_TwoInput signal X to₁, X_TwoAnd each microphone 2
₁, 2_TwoOutput signal Y₁, Y_TwoThe input / output relationship withBecauseI meanCan be requested. Here, the final required
Raw variable loss device 5₁, 5 _Two, Sound pickup side variable loss device 6₁, 6
_TwoCan be realized without having frequency characteristics.
Therefore, in actual measurement, X₁, X_TwoAnd Y₁, Y_Two
Is the short-term average power and short-term average amplitude of the signal.
Therefore, there is no problem even if A and B having no frequency characteristics are obtained.
No. If you need to have frequency characteristics,
Frequency-divides the signal, and for each divided band signal
Then, the above and subsequent means may be taken.

[0015] Note that in general different from each acoustic coupling amount between the speaker 1 _1, 1 ₂ and the microphone 2 _1, 2 _2, it is necessary to obtain the four acoustic coupling amount, this example speaker 1 _1, Based on the symmetry of the arrangement relationship between the microphone ₁₂ and the microphones 2 ₁ and 2 ₂ , the acoustic coupling amount is standardized into two, A and B, and the unknowns are two, A and B, as shown in Equation (6). That is, A and B are obtained by solving two simultaneous equations.

In measuring the echo cancellation amounts E ₁ and E ₂ , the output signals Y ₁ and Y _{1 of} the microphones 2 ₁ and 2 ₂ are used.
₂ and output signals R ₁ , R of the acoustic echo cancellers 4 ₁ , 4 _2
From Eq. ₂ , E ₁ = R ₁ / Y ₁ (8) E ₂ = R ₂ / Y ₂ (9) Similarly to the measurement of the acoustic coupling amounts A and B, the short-time average power and the short-time average amplitude of the signal can be used as Y ₁ and Y ₂ and R ₁ and R ₂ . • Reproduction sound pickup signal priority determination means In judging the priority of each reproduction signal and sound pickup signal, it is necessary to consider how priority can be assigned in order to prevent howling. is there.
For example, when the level of the reproduced signal of the first channel is large and the level of the collected signal of the second channel is large,
Both priority in the same way, for example, during the regeneration side variable loss device 5 _1, the loss of sound collection side variable loss circuit 6 ₂ results in the 0dB respectively speaker 1 ₁ and the microphone 2 ₂ corresponding to the channel If the acoustic coupling is high, howling occurs. Therefore, it is necessary not to assign a high priority to the reproducing side and the sound collecting side at the same time.

In consideration of the above, there are two methods of assigning the priority, which are advantageous for the reproduced signal and those which are advantageous for the picked-up signal. An advantageous way of assigning to the reproduction signal is to always determine only the level of the reproduction signal, and if the reproduction signal exceeds a predetermined value, raise the priority of that channel and increase the priority of all channels. In the case where it is not necessary to give priority to the reproduction signal smaller than the prescribed level, the priority of the collected signals of all the channels is increased.

Further, the advantageous assignment method for the picked-up signal is as follows.
Contrary to the above, only the level of the sound pickup signal is always determined, and when the sound pickup channel exceeds a predetermined value, the priority of the channel is raised. If it is not necessary to prioritize the sound pickup signals of all the channels below a prescribed level, a method of increasing the priority of the reproduction signals of all the channels. -Loss control means Acoustic coupling A obtained by the coupling gain measuring means described above,
B, the amount of echo cancellation E ₁ , E ₂ , and a method of determining the amount of loss in the case where the above-mentioned allocation method advantageous for the collected sound signal is used in the priority assignment by the reproduced sound collection signal priority determination means. I do.

According to a method of assigning a priority advantageous to a picked-up signal,
Then, a combination of four assignment states as shown in FIG.
There is. The loss amount is determined for each of these states. State 1 State 1, that is, each sound pickup signal of channel 1 and channel 2
Is smaller than the specified level,
LR to increase the priority of the playback signal₁= 1 (0d
B), LR_Two= 1. The stability of the whole system is calculated by the formula
The following matrix obtained based on (4)It is evaluated by. In this case, the reproducing-side variable loss device 5₁Entering
Power side-speaker 1₁-Microphone 2₁−Echo canceller
4₁-Pickup side variable loss device 6₁On the output side of the
The advantage is that the playback side variable loss device 5₁Gain LR₁= 1
A ・ E₁・ LT ₁Becomes In addition, the reproducing side variable loss device 5₁
Input side-speaker 1_Two-Microphone 2 ₁−Echo cancellation
Leaver 4₁-Pickup side variable loss device 6₁On the output side path of
Gain is LR_Two= 1, so BE₁・ LT₁Tona
You. The system is stable even if the gain of both paths is changed
At least the sum LT of the gains of these two paths₁
・ E₁(| A | + | B |) must be smaller than 1.
Similarly, the sound-collecting-side variable loss device 6_TwoThe side also has two paths
Sum of gain LT_Two・ E_Two(| A | + | B |) is less than 1
Need to be That is, LT₁<1 / (| E₁| (| A | + | B |)) (11) LT_Two<1 / (| E_Two| (| A | + | B |)) (12). In this case, M in equation (10)₁about
M₁ ^TM₁Eigenvalue λ of the matrix of₁, Λ_TwoThe size of
Take the square root of the absolute value of₁Norm of M ₁‖
When asked, $ M₁‖ <1 holds and the system is stable
Become. That is, LT is set to satisfy Expressions (11) and (12).
₁, LT_TwoAnd within that range LT ₁, LT_TwoTo
If you make it as large as possible, no howling will occur
Reproduction-side variable loss unit 5₁, 5_TwoGive to
Can be State 4 State 4, that is, the collected signals of channel 1 and channel 2 are
When both levels exceed the specified level,
LT to increase the priority of the picked-up signal₁= 1, LT_Two=
Set to 1. The stability of the whole system is calculated based on equation (4).
The resulting matrixIt is evaluated by. In this case, an exact solution may be calculated
However, because it is a little complicated, in the case of state 1
Similarly to the above, the reproducing-side variable loss device 5₁From the input side of the
Transformer 6₁LR in the path to the output side of₁・
AE₁And reproduction side variable loss device 5₁From the input side of the
Transformer 6_TwoLR in the path to the output side of₁・
BE_TwoLR₁No matter how you change
LR is required for stable₁(| A || E₁| + | B || E
_Two|) <1. Similarly, the variable loss unit on the reproduction side
5_TwoFrom the input side to the pickup side variable loss device 6₁Up to the output side
Path and playback-side variable loss device 5_TwoVariable from the input side to the sound pickup side
Loss device 6₁LR for the path to the output side of_Two(| A
｜｜ E_Two| + | B || E₁|) <1.
That is, LR₁<1 / (| E₁|| A | + | E_Two|| B |) (14) LR_Two<1 / (| E_Two|| A | + | E₁|| B |) (15). In this case, M in equation (13)_FourThe norm of
‖M_Four‖ <2, and the system
The stability of the system is not guaranteed. A damping constant of about -6 dB
LR₁, LR_TwoTo stabilize easily.
Can be. State 2 or 3 State 2, that is, the collected signal of channel 1 exceeds the specified level.
However, the collected signal of channel 2 is below the specified level.
The priority of only the collected signal of channel 1
LT to increase₁= 1. Overall system stability
The following matrix that obtains the sex based on equation (4)It is evaluated by. in this case Which is E in equation (13)._TwoLT instead of_Two
E_TwoIs equivalent to using LT_TwoAs the value of LR₁
= 1, LR_TwoLT when = 1_TwoUsing the value of LR
₁, LR_TwoIs any value less than or equal to 1_TwoIs
Sufficient loss can be given. Therefore LT_TwoIn
The same value as in state 1 is used.

By analogy with the result of state 4, that is, equation (1)
4), by substituting LT ₂ E ₂ in the formula (15) instead of E ₂

[0021]

(Equation 3)

Is obtained. Also in this case, the norm of equation (16) is
When calculated, as in state 4, ４M _Two‖ <2.
So LR₁, LR_Two-6 dB attenuation constant
Need to be multiplied. However, slightly larger than -6 dB
By multiplying by the desired damping constant Att, equation (17),
LR is easier than the calculation of equation (18)₁<Att / (| E₁|| A |) (19) LR_Two<Att / (| E₁|| B |) (20) Even if ‖M_Two‖ <1 can be satisfied.

The same discussion can be made for state 3 as for state 2. FIG. 5 summarizes the loss values assigned by the loss control means to the loss coefficients LR ₁ , LR ₂ , LT ₁ , and LT ₂ based on the above study. Here, a common attenuation constant Att is applied to all the losses except for the priority channel. Also, all given loss coefficients LR ₁ , LR
₂ , LT ₁ and LT ₂ are controlled as 1 or a positive real number smaller than 1 so as not to exceed a prescribed upper limit.

As described above, the loss coefficients LR ₁ , LR ₂ ,
Since LT ₁ and LT ₂ are determined as the required amounts due to the stability of the system, the loss amount control necessary and sufficient for suppressing the howling can be performed.

[0025]

By applying the present invention to a multi-channel audio system having two or more reproduction channels and one or more sound collection channels, stable howling suppression can be realized. In particular, since the loss amount of the variable loss unit on the playback side and the variable loss unit on the sound collection side can be given as the minimum loss amount that does not cause howling, the occurrence of intermittent feeling in two-way simultaneous communication in a communication conference etc. It can be kept to a minimum.

[Brief description of the drawings]

FIG. 1 is a diagram showing gain and loss factors involved in stability determination of a multi-channel acoustic system.

FIG. 2 is a functional configuration diagram showing an embodiment of a multi-channel acoustic coupling gain reduction device according to the present invention.

FIG. 3 is a diagram illustrating a two-channel system in which acoustic coupling between a speaker and a microphone indicates symmetry.

FIG. 4 is a diagram showing a combined state of prioritized assignment of sound pickup signals by a reproduction sound pickup signal priority determination unit.

FIG. 5 is a view showing assignment of loss coefficients in each state shown in FIG. 4;

FIG. 6 is a diagram showing an acoustic closed loop in the communication conference system.

FIG. 7 is a diagram showing a functional configuration of a conventional one-channel acoustic coupling gain reduction device.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shoji Makino 2-3-1 Otemachi, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (72) Inventor Yoichi Haneda 2-3-3, Otemachi, Chiyoda-ku, Tokyo No. 1 Nippon Telegraph and Telephone Corporation F term (reference) 5D020 CC06 5K027 AA07 BB03 DD08 DD10 DD11 DD14 5K046 AA01 BB01 HH11 HH13 HH60 HH79

Claims (7)

[Claims] 1. A sound pickup signal storage destination provided for one or more sound pickup channels from two or more speakers for respectively reproducing signals generated from reproduction signal sources provided for two or more reproduction channels. A multi-channel acoustic coupling gain reduction device for reducing the coupling gain up to one or more microphones that respectively output signals to be stored in the microphone, wherein the acoustic signals reproduced from the respective speakers are collected by the respective microphones. For a sound echo obtained as a part of each microphone output signal, a simulation signal generator for generating a simulation signal of the acoustic echo for each sound pickup channel, and subtracting each simulation signal from the output signal of each microphone. Acoustic echo canceller, and a reproduction-side variable loss connected between each reproduction signal source and each speaker. A sound-collecting-side variable loss device connected between each of the acoustic echo cancellers and each of the sound-collecting signal storage destinations; and from an input terminal to the speaker to an output terminal of the acoustic echo canceller. A coupling gain measuring means for measuring the coupling gain of the reproduced signal; and a reproduced sound pickup for judging the priority of the reproduced signal supplied from the reproduced signal source and the priority of the sound pickup signal output from each of the microphones and passed through the echo canceller. Signal priority determination means, and each of the reproduction-side variable loss devices and each of the sound collection sides based on the coupling gain measured by the coupling gain measurement means and the priority determined by the reproduction sound collection signal priority determination means. A multi-channel acoustic coupling gain reducing device, comprising: a loss control means for determining a loss of the variable loss device. 2. The apparatus according to claim 1, wherein said coupling gain measuring means is configured to measure an acoustic coupling amount from each of said speakers to each of said microphones, and to perform subtraction by said acoustic echo canceller. A multi-channel acoustic coupling gain reducing device, comprising: echo canceling amount measuring means for calculating a ratio of magnitudes of output signals from the microphones before and after the microphone. 3. The apparatus according to claim 2, wherein the acoustic coupling amount measuring means inputs the short-time average value of the acoustic coupling amounts from each speaker to each microphone as an unknown value to each of the speakers. A simultaneous equation representing the input / output relationship between the short-time average power or short-time average amplitude of the signal and the short-time average power or short-time average amplitude of the output signal of each microphone is calculated using the above-mentioned speaker and each microphone. A multi-channel acoustic coupling gain reducing device, which is a means for obtaining the average value of the acoustic coupling amounts corresponding to the unknowns by unifying and solving the unknowns based on the symmetry of the arrangement relationship of the multi-channel acoustic coupling. 4. The apparatus according to claim 1, wherein said reproduced sound pickup signal priority determining means determines a magnitude of a reproduced signal supplied from said reproduced signal source, and said reproduced signal has a higher priority. A multi-channel acoustic coupling gain reducing device having a means for setting the priority of the reproduction signal to be higher when is larger than a predetermined value set in advance. 5. The apparatus according to claim 1, wherein said reproduced sound pickup signal priority judging means judges a magnitude of a sound pickup signal output from each of said microphones and passed through an echo canceller. A multi-channel acoustic coupling gain reduction device, comprising: means for setting a higher priority of the collected signal when the collected signal is larger than a predetermined value. 6. The apparatus according to claim 1, wherein the loss amount control unit determines the reproduction signal having the higher priority determined by the reproduction sound collection signal priority determination unit or the collection signal. Relative allocation of the loss amounts of the reproduction-side variable loss device and the sound-collection-side variable loss device so as to give the sound signal a smaller loss than the lower priority reproduction signal or the sound collection signal. A multi-channel acoustic coupling gain reducing device, comprising: 7. The apparatus according to claim 1, wherein the loss amount control means includes an acoustic coupling from an input terminal of the reproduction-side variable loss device to the speaker to the microphone, and the echo cancellation. Means for controlling the insertion amount of the reproduction-side variable loss device and the sound-collection-side variable loss device so that the gain to the output end of the sound-collection-side variable loss device through the device is less than 0 dB. A multi-channel acoustic coupling gain reduction device.