JP4448423B2 - Echo suppression method, apparatus for implementing this method, program, and recording medium therefor - Google Patents

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-channel echo suppression method, apparatus, program, and recording medium that are applied to, for example, a communication conference system having a multi-channel sound reproduction system and suppress acoustic echoes that cause acoustic feedback and cause hearing problems. Is.

  With the recent increase in capacity of digital networks, a multi-channel loudspeaker type teleconferencing system that allows a plurality of people to easily participate and provide a more natural calling environment has been studied. In this system, the received voice is reproduced from the speaker and picked up by the microphone to generate an acoustic echo. If the received voice is transmitted as it is, problems such as a call failure and discomfort arise. When the signal power of the acoustic echo signal is larger than the signal power of the speaker reproduction signal, the acoustic echo causes howling and makes a call impossible. As a method of suppressing acoustic echo in this multi-channel communication conference system, there is JP-A-2003-309493 (Patent Document 1).

A communication conference system including an M (≧ 2) channel reproduction system and a two-channel sound collection system performs acoustic echo suppression with the configuration shown in FIG. That is, the reception signal from each reception terminal 1 _m (m = 1,..., M) is sent as a reproduction signal to each speaker 2 _m (m = 1,..., M) and reproduced as an acoustic signal. each microphone ₃ n through the acoustic echo path (n = 1, ..., n ) around to. The collected sound signal from the microphone 3 _n is suppressed for each sound collected signal by the M channel echo suppressor 6 _n (n = 1,..., N) and the transmission terminal 5 _n (n = 1) is transmitted as a transmission signal. ,..., N).

The internal configuration of the M channel echo suppressor 6 is shown in FIG. The M channel echo suppressor 6 estimates the ratio of the echo component in the sound collection signal for each frequency component from the M channel reproduction signal from the speaker 2 _m and the one channel sound collection signal from the microphone. The acoustic echo is suppressed by attenuating the amplitude of the collected sound signal by an amount corresponding to the acoustic echo. If the sound collection system is N-channel, N M-channel echo suppression units 6 are arranged in parallel as shown in FIG.
In the echo suppression unit 6, the reproduction signal x ₁ (k),..., X _M (k) in the time domain in the TF conversion unit 61 _m (m = 1,..., M) (where k is a variable indicating time. ) With a frame length of 2L samples, framed for each L sample, converted to the frequency domain, and spectrum X ₁ (j, f),..., X _M (j, f) (where j represents the time of the frame) Variable). In the TF conversion unit 62, the spectrum Y (j, f) is obtained by converting the collected sound signal y (k) in the time domain into the frequency domain. FIG. 11 shows the relationship between the sample time k of the signal for each L sample and the frame time j.

The echo component ratio estimation unit 63 in FIG. 2 collects sound from the reproduction signal spectrum X ₁ (j, f),..., X _M (j, f) and the sound collection signal spectrum Y (j, f). The ratio γ ² (j, f) of the echo component occupying the component is obtained, and the attenuation ratio is calculated by the attenuation ratio calculation unit 64. The multiplier 65 attenuates the amplitude of the collected sound signal for each frequency component by an amount corresponding to the echo. The FT transform unit 66 transforms the processing result in the frequency domain into the time domain, and obtains a transmission signal in which echo is suppressed. The attenuation factor can be obtained from the echo component ratio γ ² (f) by a plurality of methods, and specifically described in detail in Japanese Patent Laid-Open No. 11-331046 (Patent Document 2).

エコー成分比率推定のフローを図４に示す。
特開２００３−３０９４９３号公報 特開平１１−３３１０４６号公報 Next, a detailed configuration of the echo component ratio estimation unit 63 in FIG. 2 is shown in FIG. The decorrelation unit 631, the multi-channel reproduction signal spectrum _{X 1 (j, f),} ..., X M (j, f) the spectrum of the multi-channel having no correlation with each other from _{X 1 (j, f),} X 2 (1 ₎ (J, f),..., X _{M (M-1)} (j, f) is obtained. In the correlation removing unit 632, a spectrum Y _(m−1) (j, f) (m = 2) obtained by removing the correlation component of the _{first to (m−1)} -th channel reproduction signals from the spectrum Y (j, f) of the collected sound signal. , ..., M). In the coherence calculation unit 633, the coherence calculation unit 633 ₁ converts the reproduction signal X ₁ (j, f) of the first channel and the coherence γ _1y ² (j, f) of the collected sound signal Y (j, f) into the coherence calculation unit. At 633 _m (m = 2,..., M), the reproduction signal X _{m (m−1)} (j, f) and Y _(m−1) (j, f) (m = 2,. ) Coherence γ _{my (m−1)} ² (j, f). The echo component ratio calculation unit 634 obtains an echo component ratio γ ² (j, f) by the following equation.

The flow of echo component ratio estimation is shown in FIG.
JP 2003-309493 A JP-A-11-331046

In the above-described conventional method, the collected sound signal is framed with a fixed frame length, converted into the frequency domain by FFT, and transmitted through echo suppression processing. In this method, the transmission voice signal is buffered for the frame length, processed, and then transmitted. Therefore, there is an algorithmic delay (processing delay) determined by the frame length regardless of the processing capability of the hardware. . When this delay is large, it is very difficult to separate as a call system, so it is necessary to reduce the processing delay by shortening the frame length.
However, there is a problem that an echo component that is delayed from the frame length by the time it is reproduced from the speaker and collected by the microphone is treated as a non-echo component. Therefore, when the frame length is set to be significantly shorter than the reverberation time (about 300 ms in a normal room), the echo component ratio is set smaller, or the estimated value of the echo component fluctuates. The estimation performance is degraded, and the echo component suppression performance is degraded.

In the present invention, the ratio of echo components included in the short-time spectrum Y (j, f) of the collected sound signal is determined from the short-time spectrum X ₁ (j, f),. A method is proposed for estimation using not only _M (j, f) but also a short-time spectrum obtained from a past reproduction signal frame.
In the present invention, the current frame and the past frame of the multi-channel reproduction signal are further divided into the main component consisting of the first channel reproduction signal of the current frame and the sub-component consisting of other frames from which the correlation with the main component has been removed. The ratio of the main component echo to the collected sound signal is obtained, and the ratio of the sub component echo to the collected sound signal from which the correlation with the main component is removed is obtained. A method for estimating the echo component ratio of the channel reproduction signal is proposed.

  With this method, past signal frames can be taken into the estimation of the echo component ratio, and even when the frame length is set to be much shorter than the reverberation time, the estimation performance of the echo component ratio is avoided and the echo suppression performance is improved. Deterioration can be prevented.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. Corresponding portions in the respective drawings are given the same reference numerals, and redundant description is omitted.
[First Embodiment]
The present invention will be described in the case of an M (≧ 2) channel reproduction system and an N (≧ 1) channel sound collection system. For the N channel of the sound collection system, N transmission audio power estimators with M inputs and one output are arranged in parallel to correspond to the N channel sound collection system. In the present invention, the echo component ratio estimation unit 63 in the echo suppression unit 6 of FIG. 2 whose internal configuration is shown in FIG. 3 is replaced with an echo component ratio estimation unit 68 whose internal structure is shown in FIG.

ただし、ｍ＝１，…，Ｍ
この処理では、各信号をハニング窓等でウインドウ処理してから周波数変換してもよい。 In the following, it is assumed that the frame length is 2L samples, the shift length is L samples, and the frame time is j. The signal frame at frame time j is composed of signal samples at sample times k = jL−2L + 1 to jL. The relationship between the signal sampling time k and the frame time j at this time is as shown in FIG. An example in which the short-time spectrum X ₁ (j−1, f),..., X _M (j−1, f) one frame before is used as the spectrum obtained from the past reproduction signal frame will be described.
In the TF converter 61 _m (m = 1,..., M) in FIG. 2, the reproduction signal x _m (k) in the time domain of each channel is framed into a signal vector having a length of 2 L for each L sample, and FFT is used. For a short time.

However, m = 1, ..., M
In this processing, each signal may be subjected to frequency conversion after being windowed by a Hanning window or the like.

この処理でも、各信号をウインドウ処理してから周波数変換してもよい。
図５に内部構造が示されているエコー成分比率推定部６８において以下のステップＦ１〜７により、周波数領域の多チャネル再生信号Ｘ_ｍ（ｊ，ｆ）と周波数領域の収音信号Ｙ（ｊ，ｆ）から、周波数成分ごとに収音信号に含まれるエコー成分の比率を求める。図６にエコー成分比率を推定するためのフローを示す。 Further, the TF converter 62 converts the collected sound signal y (k) into the frequency domain and obtains a short-time spectrum.

In this processing, each signal may be subjected to window processing and then frequency conversion.
In the echo component ratio estimation unit 68 whose internal structure is shown in FIG. 5, the frequency domain multi-channel reproduction signal X _m (j, f) and the frequency domain sound collection signal Y (j, f, From f), the ratio of echo components included in the collected sound signal is obtained for each frequency component. FIG. 6 shows a flow for estimating the echo component ratio.

ただし、ｍ＝２，…，Ｍ
ここで、ε［］は、平均をとることを意味し、平均処理の一例としては、

のように、１フレーム前の処理結果と０〜１の値をとる平滑化定数βを用いる方法がある。 Step F1
The short-time spectrum X ₁ (j, f),..., X _M (j, f) of the multi-channel reproduction signal obtained from the current frame is stored in the accumulation unit 681a1 in the correlation removal unit 681 in FIG.
Step F2
The decorrelation unit 681B1, for example, short-time spectrum _X 2 multichannel reproduction signal by the following equation method _{(j, f), ...,} X M (j, f) from _X 1 (j, f) the correlation components of the The spectrum X _{2 (1)} (j, f),..., X _{M (1)} (j, f) is obtained as a part of the sub-component of the multi-channel reproduction signal spectrum.

However, m = 2, ..., M
Here, ε [] means taking an average, and as an example of the averaging process,

As described above, there is a method using a processing result of one frame before and a smoothing constant β that takes a value of 0 to 1.

ただし、ｍ＝１，…，Ｍ
なお、ｎフレーム前の短時間スペクトルＸ_１（ｊ−ｎ，ｆ），…，Ｘ_Ｍ（ｊ−ｎ，ｆ）をエコー成分比率推定に使用する場合にも、同様の計算により得られた結果を多チャネル再生信号スペクトルの副成分の一部とすればよい。 Step F3
In decorrelation unit 681B2, the spectrum _X 1 of the multi-channel playback signal before one frame stored in the storage unit 681a2 (j-1, f) , ..., from X M (j-1, f ), X 1 (j , F) to obtain a spectrum X _{1 (1)} (j−1, f),..., X _{M (1)} (j−1, f) from which the correlation with the multi-channel reproduction signal spectrum is obtained as follows. It is a part of subcomponent.

However, m = 1, ..., M
Incidentally, n frames before short-time spectrum _{X 1 (j-n, f} ), ..., X M (j-n, f) in the case of using the echo component ratio estimation results obtained by the similar calculation May be a part of the sub-component of the multi-channel reproduction signal spectrum.

Step F4
The correlation removal unit 682 obtains a spectrum Y ₍₁₎ (j, f) obtained by removing the correlation component with X ₁ (j, f) from the short-time spectrum Y (j, f) of the sound collection signal of the current frame. .

Step F5
In the coherence calculation unit 683 ₁ , the short-time spectrum X ₁ (j, f) of the first channel reproduction signal of the current frame, which is the main component of the multi-channel reproduction signal spectrum, and the spectrum Y (j, f) of the current collected sound signal ) To find the next coherence.

のうちで、相関除去された収音信号スペクトルとの誤差
｜Ｙ_（１）（ｊ，ｆ）−Ｙ＾_（１）（ｊ，ｆ）｜^２
が最小となるスペクトルである。この誤差を最小にするスペクトルは、

とし、

により求められる。さらに、次式により副成分のエコー比率を周波数成分ごとに求める。

Step F6
The sub-component echo ratio calculation unit 683 ₂ first obtains an echo component Y ^ ₍₁₎ (j, f) included in the collected sound signal spectrum Y ₍₁₎ (j, f) whose correlation has been removed. The echo component Y ^ ₍₁₎ (j, f) is a sub-component X _{2 (1)} (j, f),..., X _{M (1)} (j, f), X ₁ of the multi-channel reproduction signal short-time spectrum. ₍₁₎ (j−1, f),..., X _{M (1)} (j−1, f) linear sum

Among them, the error from the collected sound signal spectrum from which the correlation has been removed | Y ₍₁₎ (j, f) −Y ^ ₍₁₎ (j, f) | ²
Is the spectrum with the minimum. The spectrum that minimizes this error is

age,

It is calculated by. Further, the echo ratio of subcomponents is obtained for each frequency component by the following equation.

図２の減衰比算出部６４では、まず周波数成分ごとにエコー成分比率から振幅減衰率を算出し、乗算部６５で収音信号の振幅を減衰させ、エコー抑圧処理結果Ｚ（ｊ，ｆ）を得る。減衰方法の例としては次式の方法がある。

これによりエコーが抑圧される。 Step F7
In the echo component ratio calculation unit 684, the ratio of the echo component in the collected sound signal spectrum Y (j, f) is obtained from each ratio obtained in steps F5 and F6.

In the attenuation ratio calculation unit 64 of FIG. 2, first, the amplitude attenuation rate is calculated from the echo component ratio for each frequency component, the multiplication unit 65 attenuates the amplitude of the collected sound signal, and the echo suppression processing result Z (j, f) is obtained. obtain. An example of the attenuation method is the following equation.

As a result, the echo is suppressed.

このフレーム信号から、例えばフレームの一部を切出した［ｚ（ｊＬ−Ｌ＋１） … ｚ（ｊＬ）］を送信信号としてもよいし、複数のフレームをウインドウ処理してオーバーラップする区間を合成することで送信信号を得てもよい。
現時点のフレームの処理が終了すると、最後に現時点の蓄積部６８１ａ１に蓄積された再生信号情報は過去の蓄積部６８１ａ２に転送され、蓄積される。
なお、蓄積部６８１ａ内で現時点の蓄積部６８１ａ１と過去の蓄積部６８１ａ２とを特に区別し、上記のように一連の処理の最後に現時点の蓄積部６８１ａ１に蓄積された再生信号情報を過去の蓄積部６８１ａ２に転送するのではなく、１つの蓄積部６８１ａに蓄積された情報の中で最新情報を現時点の情報として処理する方法もある。また、図７に示すように処理に利用する現時点の再生信号のスペクトルを、蓄積部から取り出すのではなく、入力された再生信号のスペクトルを直接利用する方法もある。 The FT converter 66 converts the echo suppression processing result Z (j, f) in the frequency domain into a time domain frame signal as shown in the following equation.

From this frame signal, for example, [z (jL−L + 1)... Z (jL)] obtained by cutting out a part of the frame may be used as a transmission signal, or a plurality of frames are subjected to window processing to synthesize overlapping sections. The transmission signal may be obtained with
When the processing of the current frame is completed, the reproduction signal information stored last in the current storage unit 681a1 is transferred to and stored in the past storage unit 681a2.
In the storage unit 681a, the current storage unit 681a1 and the past storage unit 681a2 are particularly distinguished, and the reproduction signal information stored in the current storage unit 681a1 at the end of the series of processes as described above is stored in the past. There is also a method of processing the latest information as the current information in the information stored in one storage unit 681a instead of transferring to the unit 681a2. In addition, as shown in FIG. 7, there is a method in which the spectrum of the current reproduction signal used for processing is not extracted from the storage unit, but the input reproduction signal spectrum is directly used.

[Second Embodiment]
The present invention is a combination of an echo suppression method and an acoustic echo cancellation method using an adaptive filter, and a configuration example thereof is shown in FIG.
The M channel received signal is reproduced as an acoustic signal by the speaker 2 _m (m = 1,..., M), and goes around the microphone 3 through the acoustic echo path. At the same time, it is input to the predicted echo generator 91 of the acoustic echo canceler 9. The subtractor 92 subtracts the predicted echo signal from the collected sound signal y (k) from the microphone 3, and the residual signal is fed back to the echo path estimation unit 93 and simultaneously becomes an input signal to the echo suppression unit 6. The echo suppression unit 6 suppresses echo components as in the first embodiment, and transmits a transmission signal from the transmission terminal 5.
In this configuration, a signal (residual signal) after echo cancellation by an adaptive filter is used as an input to the echo suppression unit 6. Therefore, even in a double talk situation in which the received voice and the transmitted voice overlap, the received echo component included in the collected sound signal can be greatly reduced, and the quality of the expanded call can be improved.
Note that FIG. 8 illustrates the case of the M (≧ 2) channel reproduction system and the 1-channel sound collection system, but N similar configurations are arranged in parallel when the sound collection system has N (≧ 2) channels. This is possible.

[Third Embodiment]
The present invention is a combination of an echo suppression method and a voice switch method, and a configuration example thereof is shown in FIG.
From the reproduction signal of M channel from the speaker 2 _m and the collected sound signal of 1 channel from the microphone, a transmission signal in which echo is suppressed by the echo suppression unit 6 _n ′ (n = 1,..., N) is obtained. The non-echo signal power input to the transmission determination unit is obtained. FIG. 9 corresponds to the case where the sound collection system is N-channel, and has a configuration in which N M-channel echo suppression units 6 _n ′ are arranged in parallel.

The collected sound signal is converted into the frequency domain by the TF conversion unit 62 of the echo suppression unit 6 ′ and input to the echo component ratio estimation unit 68 and the signal power calculation unit 69. The echo component ratio estimation unit 68 estimates the ratio of echo components in the collected sound signal for each frequency component, as in the first embodiment. The estimation result is input to the attenuation ratio calculation unit 64 and simultaneously to the signal power calculation unit 69 for echo suppression. In the signal power calculation unit 69, the non-echo signal power P is calculated from the echo component ratio estimation result γ ² (j, f) and the short-time spectrum Y (j, f) of the collected sound signal output from the TF conversion unit 62. _{Find YI} . The transmission determination unit 4 determines whether or not there is a transmission by comparing the non-echo signal power P _YI with a preset threshold value P _th, and when it is determined that there is a transmission voice, the variable loss unit on the reception side Only the received signal is attenuated by 7 _m (m = 1,..., M) to obtain a reproduction signal to the speaker. When it is determined that there is no transmission voice, only the transmission signal transmitted from the transmission terminal 4 is attenuated by the variable loss unit 8 _n (n = 1,..., N).

この構成の送信信号は、エコー抑圧後に可変損失部を経た信号となるため拡声通話品質の向上が期待できる。 Here, as an example of a method for obtaining the non-echo signal power P _YI , there is the following equation.

Since the transmission signal having this configuration becomes a signal that has passed through a variable loss portion after echo suppression, an improvement in the quality of voice communication can be expected.

[Fourth Embodiment]
The present invention is a combination of an echo suppression method, a voice switch method, and an acoustic echo cancellation method using an adaptive filter, and its configuration example is shown in FIG.
The M channel received signal is reproduced as an acoustic signal by the speaker 2 _m (m = 1,..., M), and circulates to the microphone 3 _n (n = 1,..., N) through the acoustic echo path. At the same time inputted to the acoustic echo cancellation unit 9 _n. An echo component is predicted from the reproduction signal x _m (k) by the prediction echo generation unit 91, and the prediction echo signal is subtracted from the collected sound signal y (k) by the subtractor 92. The residual signal is fed back to the echo path estimation unit 93 and at the same time becomes an input signal to the echo suppression unit 6 ′. FIG. 10 corresponds to the case where the sound collection system is N-channel, and has a configuration in which N M-channel echo suppression units 6 _n ′ are arranged in parallel.

The configuration and processing method of the echo suppression unit 6 ′, the transmission determination unit 4, the reception-side variable loss unit 7 _m , and the transmission-side variable loss unit 8 _n are the same as those in the third embodiment.
Since the transmission signal having this configuration is subjected to echo suppression processing on the residual signal after echo cancellation and further undergoes a variable loss section, further enhancement of the quality of the voice call can be expected.

The figure which shows the general structure of the echo suppression apparatus of M input N output. The figure which shows the structure of an M channel echo suppression part. The figure which shows the structure of the conventional echo component ratio estimation part. The figure which shows the flow of the conventional echo component ratio estimation. The figure which shows the structure of the echo component ratio estimation part of 1st Embodiment. The figure which shows the flow of echo component ratio estimation of 1st Embodiment. The figure which shows the structure of the modification of the echo component ratio estimation part of 1st Embodiment. The figure which shows the structure of the M channel echo suppression apparatus of 2nd Embodiment. The figure which shows the structure of the echo suppression apparatus of M input N output of 3rd Embodiment. The figure which shows the structure of the echo suppression apparatus of M input N output of 4th Embodiment. The figure which shows the relationship between the sample time k of a signal, and the frame time j.

Claims (12)

In a method for predicting an echo component from a reproduction signal of a plurality of channels (M channel) and a sound pickup signal of at least one channel and suppressing the echo,
The main component is the short-time spectrum of the first channel playback signal of the current frame,
With respect to the reproduction signal from the second to the M-th channel of the current frame and the reproduction signal from the first to the M-th channel at least one frame past, from each of the short-time spectra, the short-term spectrum as the main component Remove multiple correlations to find multiple short-time spectra that make up subcomponents,
Find the ratio of the main component echo to the short-time spectrum of the collected signal,
Obtain the ratio of the echoes of subcomponents in the short-time spectrum of the collected sound signal from which the correlation with the main component has been removed,
Estimate the ratio of echo components in the short-time spectrum of the collected sound signal for each frequency from the above two ratios,
Based on the echo component ratio estimated for each frequency, the amplitude of the collected signal is attenuated by an amount equivalent to the echo for each frequency component;
An echo suppression method characterized by the above. The method of claim 1 , wherein
The echo component ratio gamma ² occupying the short-time spectrum of the collected signal ^(f), the echo of the main component is short Percentage spectrum γ _{1 2} ^(f) and subcomponent of collected signal echo is mainly From the ratio γ ₂ ² (f) of the short-time spectrum of the collected sound signal from which the correlation is removed,

Asking for,
An echo suppression method characterized by the above. The method of claim 2 , wherein
The echo component Y ^ ₍₁₎ (f) included in the short-time spectrum Y ₍₁₎ (f) of the collected sound signal from which the correlation with the principal component is removed is represented by | Y ₍₁₎ (f) -Y ^ _{( 1)} (f) | Obtain as a linear sum that minimizes ² ;
The proportion γ ₂ ² (f) of the short-time spectrum of the collected sound signal from which the echo of the subcomponent is removed from the correlation with the main component,

Asking for,
An echo canceling method characterized by the above. In the method in any one of Claims 1-3 ,
The echo suppression processing result Z (f) is calculated from the short-time spectrum Y (f) of the collected sound signal and the echo component ratio γ ² (f) occupying the short-time spectrum of the collected sound signal.

Asking for,
An echo suppression method characterized by the above. In the method in any one of Claims 1-4 ,
A residual signal between the predicted value of the echo predicted from the reproduction signal and the signal obtained from the sound collection unit is used as the sound collection signal;
An echo suppression method characterized by the above. Means for receiving a reproduction signal of a plurality of channels (M channel) and a sound pickup signal of at least one channel;
Means based on the short-time spectrum of the first channel reproduction signal of the current frame;
Correlation between the reproduction signal from the second to M-th channel of the current frame and the reproduction signal from the first to M-th channel at least one frame past from each short-time spectrum to the short-time spectrum as a main component Means for obtaining a plurality of short-time spectra constituting subcomponents ,
Means for determining the proportion of the principal component echo in the short-time spectrum of the collected signal;
Means for determining the ratio of the echoes of the subcomponents in the short-time spectrum of the collected sound signal from which the correlation with the main component is removed;
Means for estimating, for each frequency, an echo component ratio in the short-time spectrum of the collected sound signal from the two ratios;
Based on the echo component ratio estimated for each frequency, means for attenuating the amplitude of the collected signal for each frequency component by an amount equivalent to the echo,
An echo suppression apparatus comprising: The apparatus of claim 6 .
As means for estimating the echo component ratio γ ² (f) in the short-time spectrum of the collected sound signal, the ratio γ ₁ ² (f) in which the main component echo occupies the short-time spectrum of the collected signal and the sub-component echo are From the ratio γ ₂ ² (f) in the short-time spectrum of the collected sound signal from which the correlation with the main component is removed,

Means to obtain by
An echo suppressor comprising: The apparatus of claim 7 .
The short-time spectrum of the collected sound signal from which the correlation with the main component has been removed as means for obtaining the ratio γ ₂ ² (f) of the short-term spectrum of the collected sound signal from which the correlation with the main component has been removed by the echo of the subcomponent _{Y: (1)} echo component contained in the (f) _{Y ^ (1)} (f),
| Y ₍₁₎ (f) -Y ^ ₍₁₎ (f) | ²
And the ratio γ ₂ ² (f) in the short-time spectrum of the collected sound signal in which the echo of the subcomponent is removed from the correlation with the main component,

Means to obtain by
An echo suppressor comprising: In the apparatus in any one of Claims 6-8 ,
The echo suppression processing result Z (f) is obtained from the short-time spectrum Y (f) of the collected sound signal, the collected sound signal Y (f), and the echo component ratio γ ² (f) in the short-time spectrum of the collected sound signal.

Means to obtain by
An echo suppressor comprising: In the apparatus in any one of Claims 6-9 ,
Means for making a sound collection signal a residual signal between a predicted value of an echo predicted from a reproduction signal and a signal obtained from the sound collection section;
An echo suppressor comprising: Echo suppressing program for executing by a computer an echo suppressing method according to claim 1-5. The computer-readable recording medium which recorded the echo suppression program of Claim 11 .

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