JPH0746160A - Sound echo canceller - Google Patents

Abstract

PURPOSE:To provide a sound echo canceller which remarkably reduces computing quantity relating to the update of coefficient correction quantity without deteriorating sound cancellation performance and eliminates a sound echo component appearing on a transmission route. CONSTITUTION:The output of an absolute value arithmetic circuit 12 is compared with a threshold value (S1) set on the absolute value arithmetic circuit 12 to detect the absolute value amplitude of an elimination error signal, and when the output of the absolute value arithmetic circuit 12 is larger than the threshold value (S1), a first attenuation circuit 14 is selected by a change-over switch 11, and when the former is smaller than the latter, a second attenuation circuit 15 is selected. In such a way, the deterioration of converging speed of sound echo cancellation characteristic according to the dividing processing of the update of the coefficient correction quantity can be corrected by using those two kinds of attenuation circuits 14, 15, and sound echo cancellation quantity can be remarkably increased by eliminating the influence of a near-end noise irrelevant to a reception signal, which enables stable and fast sound echo cancellation to be always performed. Also, since the elimination error signal with low disturbance can be used for the detection of bidirectional communication, erroneous detection can be suppressed, and speech communication space with high quality can be provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in a communication line, a room sound field control device, and a high-quality voice communication conference device, and an acoustic echo component in which a signal on a receiving path appears in a transmitting path via an acoustic echo path. The present invention relates to an acoustic echo canceller that removes noise.

[0002]

2. Description of the Related Art Generally, an acoustic echo canceller is used in communication hygiene and long-distance telephone lines using a submarine cable.
It can be roughly divided into one that removes reflection caused by impedance mismatch of the line-to-four-line converter and one that removes reverberation due to acoustic coupling of speaker's voice in a loudspeaker telephone such as a video conference system. It is composed of a variable coefficient filter and a subtraction circuit that generate pseudo-acoustic echo. The basic operation of the acoustic echo canceller will be described below.

FIG. 6 is a diagram showing the basic structure of an acoustic echo canceller. The reception signal input terminal 1 is connected to the reception signal output terminal 2, and the reception signal of the reception signal input terminal 1 is branched and supplied to the variable coefficient filter 3 to generate a pseudo echo.
The transmission signal from the transmission signal input terminal 4 and the pseudo acoustic echo that is the output of the variable coefficient filter 3 are input to the subtraction circuit 5,
The acoustic echo component in the transmitted signal is removed, and the subtraction circuit 5
Is output to the transmission signal output terminal 6. The output of the transmission signal output terminal 6 and the signal of the reception signal input terminal 1 are input to the correction amount calculation circuit 7, and the filter coefficient of the variable coefficient filter 3 is corrected by the output of the coefficient correction amount calculation circuit 7. The reception signal is input to the reception signal input register 8 in the variable coefficient filter 3, and the sum of products of the reception signal of the reception signal input register 8 and the pseudo impulse response of the pseudo impulse response register 9 is obtained by the sum of products circuit 10. The output of the sum-of-products circuit 10 is output as a pseudo acoustic echo. Received signal output terminal 2
And the transmission signal input terminal 4 is 2 for a long-distance telephone line.
A line-to-line converter is connected to the speaker and microphone in the case of a loudspeaker telephone system.

Assuming that the signal propagation characteristic of the acoustic echo path is linear and represented by an FIR type digital filter, if the impulse response h (t) and the input received signal x (t) are used, the sampling time interval is Is T, and the acoustic echo y _{k at} time kT is represented by y _k = h′x _k (1). However, h = [h ₁ , h ₂ , ..., H _n ] '(2) -1 x = [x _{k -1} , ..., x _{k -n} ]' (2) -2 ': It is the transposition of Khutor.

On the other hand, the estimated value of h at time kT is h
If s _k , the estimated value ys _k of y _k is given by ys _k = hs _k ′ x _k (3). In the acoustic echo canceller, when there is a voice signal in the reception signal input terminal 1 and there is no voice signal in the transmission signal input terminal 4 and only acoustic echo exists, the echo elimination operation is performed as an adaptive operation state. A learning identification method is generally adopted for this adaptive operation algorithm. Successive correction of hs _k by the learning identification method is performed by _{hs k +1 = hs k + α} (x k e k) / x k 'x k (4). However, e _k = y _k −y s _k ′, 0 <α ≦ 1 (5), and e _k is called residual acoustic echo. Such a calculation operation is processed in the coefficient correction amount calculation circuit 7. The contents of the pseudo impulse response register 9 include the variable coefficient series h.
s _k is stored. α is a correction loop gain for determining the sensitivity of estimation, and a larger correction amount can be given as it approaches 1.0, but it needs to be changed depending on near-end noise and line conditions. Also, the acoustic reverberation characteristic of the sound field is calculated as
When expressed with a digital filter,
It has a long structure of 000 taps and a variable coefficient sequence h
Since the amount of calculation involved in updating the modification amount of s _k becomes enormous and cannot be realized by a small-scale hardware, the variable coefficient sequence h
A method is adopted in which s _k is divided into several stages to reduce the update calculation amount in one step. FIG. 7 shows acoustic echo canceling characteristics when the two-division processing is performed. The case where division processing is not used for comparison is also described. The contents of division are as follows, where N is the total number of variable coefficient sequences.

[0006] _{hs1 k: 0~N / 2 hs2 k} : N / 2~N updating algorithm by applying the divided ranges, Equation (4)
More, expressed as _{hs1 k +1 = hs1 k + α} (x k e k) / x k 'x k (6) hs2 k +1 = hs2 k + α (x k e k) / x k' x k (7) things can be, it is an adaptive algorithm to update the entire variable coefficient series hs _k in two steps. Therefore, the calculation amount in one step can be reduced to 1/2, and of course, if the number of divisions is increased, the calculation amount can be reduced in proportion to it.

[0007]

If the variable coefficient sequence hs _k is updated by performing a division process, the amount of calculation can be reduced, but the variable coefficient that is not updated in one step causes pseudo acoustic echo. Error is generated, and as a result, the acoustic echo canceling characteristics deteriorate, and it takes about 2 to converge.
Double the time required. Deterioration of the convergence speed is likely to affect the tracking performance when fluctuations occur in the acoustic echo path, and there is a high possibility that residual acoustic echo with a relatively large amplitude may exist on the transmission path. There is a risk of false positives. In addition, since near-end noise that is completely uncorrelated with the received signal as an explanatory variable is input from the transmission signal input terminal in the form of being superimposed together with the acoustic echo, the amount of acoustic echo cancellation is limited and an offensive residual echo sound is generated. However, there is a problem that it is not possible to remove acoustic echo with high accuracy and high quality.

The present invention has been made in view of the above points, and eliminates the above problems, compensates for the deterioration of the convergence speed due to the coefficient correction amount division update, and causes disturbances such as near-end noise other than the explanatory variables. To eliminate the influence and increase the amount of acoustic echo cancellation,
Moreover, it is an object of the present invention to provide an acoustic echo canceller that improves the stability of two-way communication detection.

[0009]

SUMMARY OF THE INVENTION The present invention is to solve these problems and comprises a reception signal input terminal, a reception signal output terminal, a transmission signal input terminal, and a transmission signal output terminal. A variable coefficient filter that receives the received signal input from the received signal input terminal, a pseudo impulse response register that stores a coefficient sequence of the variable coefficient filter,
A product-sum operation circuit that performs a convolution integration operation between the contents of the pseudo impulse response register and the input signal from the reception signal input terminal, a pseudo echo generated by the product sum operation circuit, and an echo from the reception signal output terminal. A subtraction circuit that calculates a residual echo by calculating the difference from the signal, and divides the coefficient sequence of the pseudo impulse response register into N blocks so as to supply an approximate value with the echo signal, and divides the coefficient by N times. In a sound echo canceling apparatus including a coefficient correction amount calculation circuit that performs a division process such that the entire sequence is automatically updated, a changeover switch to which a removal error signal output from the subtraction circuit is input, An absolute value calculation circuit for detecting the absolute value amplitude of the removal error signal and a threshold value (S1) set by the calculation result calculated by the absolute value calculation circuit are provided. On the other hand, when the output of the absolute value calculation circuit is larger than the threshold value (S1), the first attenuation circuit is selected by the changeover switch, and when the output is smaller, the second attenuation circuit is selected by the output terminal of the changeover switch. Thus, the acoustic echo canceller is provided, in which the cancellation error signal output to the transmission signal output terminal is gradually reduced to zero.

A first moving average power calculating circuit for calculating a moving average power of a constant section of the input signal input from the receiving signal input terminal, and a receiving signal output from the first moving average power calculating circuit. A second moving average power calculating circuit for calculating an average power (Px) and a moving average power of a fixed section of the transmitting signal input to the transmitting signal input terminal; and a second moving average power calculating circuit Of the transmission signal average power (Py) output by the above and the ratio Px / Py of the reception signal average power Px and the transmission signal average power Py are obtained, and a threshold value (S2) preset in the input / output evaluation circuit is obtained. )
In the following cases, a coefficient correction amount calculation operation determination circuit for continuing the operation of the coefficient correction amount calculation circuit, and when it is a threshold value (S2) or more, it is determined to be a bidirectional communication state, and the operation of the coefficient correction amount calculation circuit is suspended. The acoustic echo canceller according to claim 1, further comprising: an attenuation circuit operation determination circuit that outputs the subtraction circuit output as it is to the transmission signal output terminal without passing through the first attenuation circuit.

A short-time moving average power calculation circuit for calculating a short-time moving average power of the removal error signals output from the first attenuation circuit and the second attenuation circuit, and the short-time moving average power calculation. "1" is output when the removal error signal short-time average power Pecc output from the circuit is larger than the threshold value (S3) preset in the removal error evaluation circuit, and "0" is output when it is smaller. And a multivariate evaluation circuit for comparing the data output from the removal error evaluation circuit with the data output from the input / output evaluation circuit. The evaluation circuit outputs when the output of the input / output evaluation circuit is "1" and the output of the removal error evaluation circuit is "1" and when the output of the input / output evaluation circuit is "0" and the output of the removal error evaluation circuit. But only in two ways when the "1""
The acoustic echo canceller according to claim 1 or 2, wherein 1 "is output and data is transmitted to the coefficient correction amount calculation operation determination circuit and the attenuation circuit operation determination circuit.

The acoustic echo canceller according to any one of claims 1 to 3, wherein the slope of the attenuation characteristic of the output data output from the first attenuation circuit and the second attenuation circuit is less than 1.

In the one-way communication state and the two-way communication state or the non-two-way communication state, the removal error signal output from the subtraction circuit having the absolute value amplitude equal to or less than the threshold value (S1) is always applied to the second attenuation circuit. The acoustic echo canceller according to any one of claims 1 to 4, wherein the acoustic echo canceller is linearly proportional to the constant.

[0014]

According to the present invention, by using the non-linear conversion processing having two kinds of attenuation characteristics by the above means, it is possible to correct the deterioration of the convergence speed of the acoustic echo canceling characteristics due to the division processing for updating the coefficient correction amount, and to explain the explanatory variables. Since the influence of near-end noise that is completely uncorrelated with the received signal can be eliminated and the amount of acoustic echo cancellation can be greatly increased, it is possible to always realize stable and high-speed acoustic echo removal. Further, since the removal error signal with less disturbance is used for bidirectional communication detection, erroneous detection can be suppressed, and a high quality voice communication space can be provided.

[0015]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a first acoustic echo canceller of the present invention. As shown in FIG. 1, according to the present invention, the conventional reception signal input terminal 1, reception signal output terminal 2, variable coefficient filter 3, transmission signal input terminal 4, subtraction circuit 5, transmission signal output terminal 6, coefficient correction are provided. A switch 11, which has the same configuration as the acoustic echo canceling device that employs the learning identification method as an adaptive algorithm, which includes the quantity calculation circuit 7, the reception signal input register 8, the pseudo impulse response register 9, and the product-sum circuit 10. Absolute value calculation circuit 1
2, an absolute value determination circuit 13, a first attenuation circuit 14, a second attenuation circuit 15, and a non-linear conversion circuit 16 are added.

The reception signal input terminal 1, the transmission signal output terminal 6, the reception signal arriving at the reception signal input terminal 1, and the reception signal output terminal for transmitting the reception signal to an unknown acoustic echo path. 2, the reception signal transmitted from the reception signal output terminal 2, the echo that is a response to the reception signal, the transmission signal input terminal 4 that collects the echo, and the adaptive digital filter The pseudo impulse response register 9 storing a coefficient sequence, and the sum-of-products arithmetic circuit 10 for performing a convolution integral operation on the contents of the pseudo impulse response register 9 and the contents of the reception signal input register 8 storing the reception signal. , The subtraction circuit 5 for taking the difference value between the pseudo echo generated by the product-sum operation circuit and the echo, and the relation between the pseudo impulse response register so that the adaptive digital filter supplies an approximate value of the echo. In the acoustic echo canceling device configured by dividing the number sequence into N blocks and performing the division processing such that the entire coefficient sequence is automatically updated N times, The removal error signal output from the circuit 5, the changeover switch that receives the removal error signal, the absolute value calculation circuit 12 that detects the absolute value amplitude of the removal error signal, and the absolute value calculation circuit 12 is compared with the set threshold value S1, and when the output of the absolute value calculation circuit 12 is larger than the threshold value S1, the output terminal a of the changeover switch is selected, and conversely, the absolute value calculation circuit 12 of the absolute value calculation circuit 12 is selected. The absolute value determination circuit 13 that selects the output terminal b of the changeover switch when the output is smaller than the threshold value S1.
, The first attenuation circuit 14 connected to the output terminal a of the changeover switch, and the output terminal b of the changeover switch
The non-linear conversion processing circuit 16 composed of the second attenuation circuit 15 connected to the second attenuation circuit 15 is inserted between the subtraction circuit 5 and the transmission signal output terminal 6, and the first and second attenuation circuits An acoustic echo canceller characterized in that control is performed so that a cancellation error signal output from a circuit and appearing at the transmission signal output terminal 6 becomes extremely close to zero.

FIG. 2 is a block diagram showing the configuration of the second acoustic echo canceller of the present invention. As shown in FIG.
The present invention includes a reception signal input terminal 1, a reception signal output terminal 2,
Variable coefficient filter 3, transmission signal input terminal 4, subtraction circuit 5, transmission signal output terminal 6, coefficient correction amount calculation circuit 7, reception signal input register 8, pseudo impulse response register 9,
The acoustic echo removal of FIG. 1 including the sum-of-products circuit 10, changeover switch 11, absolute value calculation circuit 12, absolute value determination circuit 13, first attenuation circuit 14, second attenuation circuit 15, and non-linear conversion circuit 16. A device having the same configuration as that of the device includes a first moving average power calculation circuit 17, a second moving average power calculation circuit 18, an input / output evaluation circuit 19, a coefficient correction amount calculation operation determination circuit 20, and an attenuation circuit operation determination circuit. 21 is added to the configuration.

The first moving average power calculating circuit 17 for calculating the moving average power of the receiving signal in a certain section, and the receiving signal average power Px output from the first moving average power calculating circuit 17, The transmission signal input to the transmission signal input terminal 6, the second moving average power calculation circuit 18 for calculating the moving average power of the transmission signal in a certain section, and the second moving average power calculation circuit The average power P of the transmission signal output from 18
y, the reception signal average power Px and the transmission signal average power Py
The ratio Px / Py of the input / output evaluation circuit 19 and the output of the input / output evaluation circuit 19 that outputs “0” if it is equal to or more than a preset threshold S2 and “1” if it is less than the threshold S2 If it is "1", it is judged to be the bidirectional communication state, and the operation of the coefficient correction amount calculation circuit 7 is stopped, and if the output is "0", the coefficient correction amount calculation operation determination is made to continue the operation of the coefficient correction amount calculation circuit 7. On the other hand, if the output of the circuit 20 and the input / output evaluation circuit 19 is “1”, it is judged that the communication is in the bidirectional communication state, and the output of the subtraction circuit 5 is directly transmitted to the transmitter without passing through the first attenuation circuit 14. An acoustic echo canceller characterized in that the attenuation circuit operation determination circuit 21 to be output to the signal output terminal 6 is added.

FIG. 3 is a block diagram showing the configuration of the third acoustic echo canceller of the present invention. As shown in FIG.
The present invention includes a reception signal input terminal 1, a reception signal output terminal 2,
Variable coefficient filter 3, transmission signal input terminal 4, subtraction circuit 5, transmission signal output terminal 6, coefficient correction amount calculation circuit 7, reception signal input register 8, pseudo impulse response register 9,
Sum of products circuit 10, changeover switch 11, absolute value calculation circuit 12, absolute value determination circuit 13, first attenuation circuit 14, second attenuation circuit 15, non-linear conversion processing circuit 16, first moving average power operation circuit 17 , Second moving average power calculation circuit 1
8. Input / output evaluation circuit 19 Coefficient correction amount calculation operation determination circuit 2
0, and a short-time moving average power calculation circuit 22, a removal error evaluation circuit 23, and a multivariate evaluation circuit 24 are added to the device having the same configuration as the acoustic echo removal device of FIG. It has been configured.

The short-time moving average power calculation circuit 22 for calculating the short-time moving average power of the removal error signal processed by the non-linear conversion processing circuit 16 and the short-time moving average power calculation circuit 22 are output. Removal error signal short-time average power Pecc and removal error signal short-time average power Pecc
When the removal error signal short-time average power Pecc is larger than the threshold S3, "1" is output, and conversely, the removal error signal short-time average power Pcc is output.
When the ecc is smaller than the threshold value S3, the removal error evaluation circuit 23 which is set to output "0", the output of the removal error evaluation circuit 23 and the output of the input / output evaluation circuit 19 are input. The multivariate evaluation circuit 24 and the multivariate evaluation circuit 24 evaluate the removal error when the output of the removal error evaluation circuit 23 is "1" and the output of the input / output evaluation circuit 19 is "1". Only when the output of the circuit 23 is "1" and the output of the input / output evaluation circuit 19 is "0", "1" is set.
Is output, and in the case of other combinations, “0” is output.

The outputs of the multivariate evaluation circuit 24 are the coefficient correction amount calculation operation determination circuit 20 and the attenuation circuit operation determination circuit 21.
An acoustic echo canceller characterized by being input to both sides.

FIG. 4 is a diagram showing the input / output characteristics of the non-linear conversion processing circuit 16 of FIGS. 1, 2 and 3 in the one-way communication state as shown in the embodiment of the present invention. An input signal smaller than the threshold value S1 determined by the absolute value and not zero is output as the signal attenuated as shown in FIG. 4 by the second attenuator circuit 15 having a slope extremely close to zero. Also, the threshold value S1
A larger input signal is output as a signal attenuated by the first attenuator circuit 14 having a slope of less than 1 as shown in FIG. Therefore, the deterioration of the convergence speed of the acoustic echo canceling characteristic due to the division processing for updating the coefficient correction amount is compensated. Then, since the input signal of the non-linear conversion processing circuit 16 is not zero and the output signal is not zero, the sound quality deterioration due to the switching noise is suppressed.

FIG. 5 is a diagram showing the input / output characteristics of the non-linear conversion processing circuit 16 in FIGS. 2 and 3 showing the embodiment of the present invention. In the one-way communication state, the characteristics shown in FIG. This characteristic is the same as the characteristic shown in FIG. Then, in the two-way communication state, the characteristics shown in FIG. An input signal smaller than the threshold value S1 exhibits the same input / output characteristics as shown in FIG. 9A, but an input signal larger than the threshold value S1 is output without any processing. In other words, a tilt of 1 is given. Therefore, it is possible to suppress the influence of disturbance such as near-end noise in both the one-way communication state and the two-way communication state and prevent the sound quality from deteriorating.

[0024]

As described above in detail, according to the present invention, the following excellent effects are expected.

(1) Since the deterioration of the convergence speed of the acoustic echo canceling characteristic due to the division processing for updating the coefficient correction amount can be corrected, the acoustic echo removal can be speeded up.

(2) Without degrading the acoustic echo canceling performance,
Since the internal calculation amount of the adaptive algorithm can be significantly reduced, the hardware can be realized with a small configuration.

(3) By using the removal error signal after the non-linear conversion processing as one of the detection evaluation values of the two-way communication, not only in the steady state but also in the initial state of the operation or the transient state such as when the echo path changes. The risk of erroneous detection is reduced, and high-speed and highly accurate bidirectional communication detection can be realized.

(4) Through the unidirectional communication state and the bidirectional communication state, the output of the non-linear conversion circuit exists unless the transmission signal is zero, so that there is no annoying switching noise and a high quality voice communication space is provided. I can do things.

(5) Since near-single noise can be suppressed even in a two-way communication state, it is possible to eliminate an unnatural increase or decrease of background noise when switching between the one-way communication state and the two-way communication state. It is possible to provide a high quality voice communication space.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration example of a first acoustic echo canceller of the present description.

FIG. 2 is a block diagram showing a configuration example of a second acoustic echo canceller of the present description.

FIG. 3 is a block diagram showing a configuration example of a third acoustic echo canceller of the present description.

FIG. 4 is a diagram showing an input / output characteristic in a unidirectional communication state of the non-linear conversion processing circuit in FIGS. 1, 2 and 3 showing an embodiment of the present invention.

FIG. 5 is a diagram showing input / output characteristics of the non-linear conversion processing circuit in FIGS. 2 and 3 showing the embodiment of the present invention.

FIG. 6 is a block diagram showing a basic configuration of an acoustic echo canceller using a conventional general learning identification method.

FIG. 7 is a diagram showing acoustic echo cancellation characteristics due to input of a white noise signal when a division process is performed for updating the coefficient correction amount.

[Explanation of symbols]

 1 reception signal input terminal 2 reception signal output terminal 3 variable coefficient filter 4 transmission signal input terminal 5 subtraction circuit 6 transmission signal output terminal 7 coefficient correction amount calculation circuit 8 reception signal input register 9 pseudo impulse response register 10 sum-of-products circuit 11 Changeover switch 12 Absolute value calculation circuit 13 Absolute value determination circuit 14 First attenuation circuit 15 Second attenuation circuit 16 Non-linear conversion processing circuit 17 First moving average power calculation circuit 18 Second moving average power calculation circuit 19 Input / output Evaluation circuit 20 Coefficient correction amount calculation operation determination circuit 21 Attenuation circuit operation determination circuit 22 Short-time moving average power calculation circuit 23 Removal error evaluation circuit 24 Multivariate evaluation circuit

Claims (5)

[Claims] 1. A reception signal input terminal, a reception signal output terminal, a transmission signal input terminal, a transmission signal output terminal, and a variable coefficient filter which receives the reception signal input from the reception signal input terminal. A pseudo impulse response register that stores a coefficient sequence of the variable coefficient filter, a sum of products arithmetic circuit that performs a convolution integral operation of the contents of the pseudo impulse response register and an input signal from the reception signal input terminal, and the sum of products A subtraction circuit that calculates a residual echo by calculating the difference between the pseudo echo generated by the arithmetic circuit and the echo signal from the reception signal output terminal, and the pseudo impulse response so as to supply an approximate value to the echo signal. The coefficient series of the register is divided into N blocks, and the coefficient series is composed of a coefficient correction amount calculation circuit for performing division processing so that the entire coefficient series is automatically updated N times. In the echo echo canceller, a changeover switch to which the removal error signal output from the subtraction circuit is input, an absolute value calculation circuit for detecting the absolute value amplitude of the removal error signal, and a calculation by the absolute value calculation circuit The threshold value (S
1) and the output of the absolute value calculation circuit is the threshold value (S
1) When it is larger, the first attenuating circuit is selected by the changeover switch, and when it is smaller, the second attenuating circuit is selected by the output terminal of the changeover switch and is output to the transmission signal output terminal. An acoustic echo canceller characterized in that a cancellation error signal is gradually reduced to zero. 2. A first moving average power calculation circuit for calculating a moving average power of a constant section of an input signal input from the reception signal input terminal, and output from the first moving average power calculation circuit. A second moving average power calculating circuit for calculating the receiving signal average power (Px) and a moving average power of a fixed section of the transmitting signal input to the transmitting signal input terminal; and the second moving average power. The transmission signal average power (Py) output by the arithmetic circuit and the ratio Px / Py between the reception signal average power Px and the transmission signal average power Py are obtained, and the threshold value is preset in the input / output evaluation circuit. (S2)
In the following cases, a coefficient correction amount calculation operation determination circuit for continuing the operation of the coefficient correction amount calculation circuit, and when it is a threshold value (S2) or more, it is determined to be a bidirectional communication state, and the operation of the coefficient correction amount calculation circuit is suspended. 2. The acoustic echo canceller according to claim 1, further comprising: an attenuation circuit operation determination circuit that outputs the subtraction circuit output as it is to the transmission signal output terminal without passing through the first attenuation circuit. apparatus. 3. A short-time moving average power calculation circuit for calculating a short-time moving average power of a removal error signal output from the first attenuating circuit and the second attenuating circuit, and the short-time moving average. "1" is output when the removal error signal short-time average power Pecc output from the power calculation circuit is larger than the threshold value (S3) preset in the removal error evaluation circuit, and "0" is output when it is small. And a multivariate evaluation circuit for comparing the data output from the removal error evaluation circuit with the data output from the input / output evaluation circuit. The multivariate evaluation circuit is configured such that when the output of the input / output evaluation circuit is "1" and the output of the removal error evaluation circuit is "1", and the output of the input / output evaluation circuit is "0" and the removal error evaluation circuit of the removal error evaluation circuit is "1". Out But only in two ways when the "1""
3. The acoustic echo canceller according to claim 1, wherein 1 "is output and data is transmitted to the coefficient correction amount calculation operation determination circuit and the attenuation circuit operation determination circuit. 4. The acoustic echo according to claim 1, wherein the slope of the attenuation characteristic of the output data output from the first attenuation circuit and the second attenuation circuit is less than 1. Removal device. 5. In the one-way communication state and the two-way communication state or the non-two-way communication state, the removal error signal output from the subtraction circuit having an absolute value amplitude equal to or less than a threshold value (S1) is always used as the second error signal. The acoustic echo canceller according to claim 1, wherein the acoustic echo canceller is linearly proportional to the constant of the attenuation circuit.