JP2009188724A - Echo suppression gain estimation method, echo canceler using the same, device program and recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress generation of musical noise robust to audio distortion. <P>SOLUTION: An echo suppression gain estimation method includes: a similarity coefficient computation step of determining a similarity coefficient by normalizing an inner product value of playback signal spectrum and sound collection signal spectrum with a product of magnitudes of the playback signal spectrum and of the sound collection signal spectrum; and an echo suppression gain computation step of entering the sound collection signal spectrum, the similarity coefficient and an echo power estimation value and computing a gain coefficient, for suppressing echo, that becomes a smaller value as the similarity coefficient gets closer to 1. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an echo canceller used in a communication conference system having an acoustic reproduction system, an echo suppression gain estimation method applied thereto, a program thereof, and a recording medium.

  Echo suppression processing based on short-time spectral amplitude (STSA) estimation estimates a gain coefficient that suppresses echoes assuming no correlation between echo and near-end talker speech, and echoes in the amplitude frequency domain It is a method to suppress. An example of the functional configuration of the echo canceller 80 using this echo suppression gain estimation method is shown in FIG. 8 and its operation will be briefly described.

  The echo canceller 80 includes a reproduction signal frequency analysis unit 81, a sound pickup signal frequency analysis unit 82, an echo power calculation unit 83, a gain calculation unit 84, a multiplication unit 85, and a frequency synthesis unit 86. The reproduction signal x (k) is a signal having a discrete value at a sampling frequency of 16 kHz, for example, and is converted into an acoustic signal by the speaker 1. Note that an AD converter that converts the reproduction signal into discrete values and a DA converter that converts the discrete values into continuous values are omitted.

The reproduction signal frequency analysis unit 81 collects 256 discrete values of the reproduction signal to form one frame, performs frequency analysis by 1/2 overlap addition, and converts the frequency range up to 8 kHz in units of frames into 128 reproduction signal spectra X Convert to _ω . (K) is a frame number, and ω is a frequency spectrum number (1 to 128) obtained at an interval of 64 Hz in this example.

The collected sound signal y (k) collected by the microphone 2 is superimposed on the near-end speaker signal s (k) by the echo d (k) generated by reproducing the reproduced signal x (k) from the speaker 1. Signal. The collected sound signal y (k) is converted into a collected sound signal spectrum Y _ω by the collected sound signal frequency analysis unit 82 in the same manner as the reproduction signal x (k).

The echo power calculation unit 83 calculates an echo power estimated value | D _ω ^ | ² shown in Expression (1) using the reproduction signal spectrum X _ω and the collected sound signal spectrum Y _ω as inputs. ^ Represents an estimated value, but the notation is correct as shown in the equations and figures.

ここで、｜Ｈ_ω＾｜^２は音響結合量の推定値であり、｜Ｈ_ω＾｜^２￣は１フレーム過去の音響結合量の推定値である。ｍｉｎ｛ ， ｝は最小値を選択する関数である。したがって、｜Ｈ_ω＾｜^２は隣接するフレーム間で小さい方の音響結合量がその推定値になる。

Here, | H _ω ^ | ² is an estimated value of the acoustic coupling amount, and | H _ω ^ | ² ￣ is an estimated value of the acoustic coupling amount in the past of one frame. min {,} is a function for selecting the minimum value. Therefore, | H _ω ^ | ² is the estimated value of the smaller acoustic coupling amount between adjacent frames.

The gain calculation unit 84 outputs the gain coefficient G _ω shown in Expression (2) with the collected sound signal spectrum Y _ω and the echo power estimated value | D _ω ^ | ² as inputs. The gain coefficients G _omega takes a real value from 0 to 1, when the echo component in the collected signal spectrum Y _omega many small values, takes a large value when there are many components other than the echo components.

The multiplication unit 85 multiplies the collected sound signal spectrum _Yω by a gain coefficient _Gω . Since the gain coefficient _Gω when there are many echo components becomes a small value, the output signal of the multiplier 85 becomes an echo cancellation signal spectrum _Eω with the echo components suppressed. The echo cancellation signal spectrum E _ω corresponding to each frequency component ω is re-synthesized into a time-domain output signal e (k) in the frequency synthesizer 86 (see, for example, Non-Patent Document 1).

Here will be described the derivation basis of formula (2) for calculating a gain factor G _omega. The gain coefficient _Gω is derived based on, for example, the assumption of the Wiener filter method (hereinafter referred to as “Wiener Filter”). WF method suppresses an echo by estimating the gain factor G _omega which minimizes the evaluation value ε of the formula (3).

式（３）をＧ_ωで微分すると式（４）で表わせる。

式（４）を０と置いた式からゲイン係数Ｇ_ωを求めると式（５）となる。

It can be expressed by the formula (4) and equation (3) is differentiated in the G _ω.

When the gain coefficient _Gω is obtained from an equation in which equation (4) is set to 0, equation (5) is obtained.

Here, <and> mean inner products. Assuming that the echo power D _ω and the echo cancellation signal spectrum E _ω are uncorrelated, that is, the result of setting <D _ω , E _ω > = 0 is the above equation (2) for _obtaining the gain coefficient G _ω. is there.
Sakauchi, S., Haneda, Y., Kataoka, A., “Echo suppression processing based on STSA estimation, gain emphasis method” (1), 1vol.J88-A, no.6, Jun.2005, p695-703

The assumption of the WF method <D _ω , E _ω > = 0 is more accurate as the time series interval is longer. However, since the echo and the near-end speaker signal s (n) are speech, they are non-stationary signals. Therefore, the gain coefficient _Gω cannot be calculated using a long time such that <D _ω , E _ω > = 0. As a result, an error occurs when the inner product value of the echo power _Dω and the echo cancellation signal spectrum _Eω is not 0, and distortion occurs in the echo cancellation signal spectrum _Eω . When this distortion is converted into a signal in the time domain, it may cause the generation of musical noise that sounds like a “curl”.

  The present invention has been made in view of these points, and an object thereof is to provide an echo suppression gain estimation method for suppressing the generation of musical noise, an echo canceller using the method, a program thereof, and a recording medium. To do.

  An echo suppression gain estimation method according to the present invention includes a reproduction signal frequency analysis stage for converting a reproduction signal into a frequency domain reproduction signal spectrum, and a sound collection signal frequency analysis stage for converting a sound collection signal into a frequency domain sound collection signal spectrum. An echo power estimation stage for calculating an echo power estimation value by inputting the reproduction signal spectrum and the collected sound signal spectrum, and calculating an inner product value of the reproduction signal spectrum and the collected sound signal spectrum for each of the reproduced signal spectrum and the collected sound signal spectrum. The similarity coefficient calculation stage that calculates the similarity coefficient normalized by the product of the magnitude, the gain coefficient that suppresses the echo, the sound collection signal spectrum, the similarity coefficient, and the echo power estimation value as inputs, and the similarity coefficient And an echo suppression gain calculation stage for calculating so as to be smaller as the value approaches 1.

  According to the echo suppression gain estimation method of the present invention, since the similarity coefficient is a value representing the proportion of echo components in the collected sound signal, the gain coefficient decreases as the similarity coefficient approaches 1, and the echo is suppressed. The At the same time, the gain coefficient obtained in this way operates to reduce the loss of the near-end speaker signal s (k). Therefore, it is possible to perform echo suppression with less musical noise generation, which is more robust against voice distortion than the conventional method.

Embodiments of the present invention will be described below with reference to the drawings. The same reference numerals are given to the same components in a plurality of drawings, and the description will not be repeated.
[Basic idea of the invention]
Prior to the description of the embodiments, the basic idea of the echo suppression method of the present invention will be described. The present invention, evaluation amount in light of the correlation of the echo-power D _omega was not conventionally considered echo-canceled signal spectrum E _omega epsilon to obtain a minimum solution of (formula (3)), the echo suppression gain estimator high The idea is to improve accuracy.

When the above equation (5) is modified, the gain coefficient _Gω can be expressed by equation (6).

Here, r _ω represents the complex coherence between the echo power D _ω and the echo cancellation signal spectrum E _ω . If the unknown vector D _ω is eliminated from r _ω using D _ω = H _ω ^* X _ω , it can be expressed by equation (7).

そしてゲイン係数を式（９）に示すように与える。

Here, * represents a complex conjugate. As can be seen from equation (7), even if _Dω is eliminated, it is difficult to obtain _rω because there is an unknown variable _Hω . Therefore, in the present invention, attention is paid to the fact that H _ω can be erased as shown in the equation (8) if the absolute value.

The gain coefficient is given as shown in equation (9).

| R _ω | is the inner product value of the reproduction signal spectrum X _ω and the collected sound signal spectrum Y _ω , which is obtained by calculating the reproduction signal spectrum size ‖X _{ω 、} and the collected signal spectrum size (nom) ‖ Y _ω ‖. The value normalized by the product (hereinafter, the absolute value symbol of | r _ω | is omitted). The r _ω at this time may be calculated by paying attention not only to the time axis direction but also to the frequency axis direction. This value indicates the ratio of echo components in the collected sound signal spectrum. Hereinafter, r _ω is referred to as a similarity coefficient. Note that ^p in G _ω ^p is a symbol for distinguishing from the gain coefficient G _{ω in} Equation (2).

The similarity coefficient r _ω approaches 0 at the time of double talk, and if this value is used to determine the gain coefficient using Equation (9), it can be a gain coefficient that reduces the loss of the near-end speaker signal. Therefore, it is possible to expect echo suppression with less generation of musical noise that is more robust against voice distortion than the conventional method.

  FIG. 1 shows a functional configuration example of an echo canceling apparatus 10 using the echo suppression gain estimation method of the present invention as a first embodiment. The operation flow is shown in FIG. The echo cancellation apparatus 10 includes a reproduction signal frequency analysis unit 81, a sound pickup signal frequency analysis unit 82, an echo power estimation unit 83, a similarity coefficient calculation unit 12, an echo suppression gain calculation unit 14, a multiplication unit 85, And a frequency synthesizer 86. The echo canceling apparatus 10 of this example is realized by reading a predetermined program into a computer composed of, for example, a ROM, a RAM, a CPU, and the like, and executing the program by the CPU.

The echo cancellation apparatus 10 is obtained by replacing the gain calculation unit 84 of the echo cancellation apparatus 80 described in the prior art with a similarity coefficient calculation unit 12 and an echo suppression gain calculation unit 14. The reproduction signal frequency analysis unit 81 converts the reproduction signal x (k) into a reproduction signal spectrum _Xω in the frequency domain (step S81). Collected sound signal frequency analyzer 82 converts the collected sound signal y (k) in the collected sound signal spectrum Y _omega in the frequency domain (step S82).

The echo power estimation unit 83 calculates the echo power estimated value | D _ω ^ | ² shown in the above equation (1) by using the reproduction signal spectrum X _ω and the collected sound signal spectrum Y _ω as inputs (step S83).
The similarity coefficient calculation unit 12 receives the reproduction signal spectrum X _ω and the collected sound signal spectrum Y _ω as input, and uses the inner product <X _ω , Y _ω > by Equation (10), for example, and the reproduction signal spectrum size ‖ X _ω ‖ And the magnitude of the collected sound signal spectrum ‖ Y _ω例_えば are calculated by, for example, Expression (11) and Expression (12), respectively.

ここで、＊は複素共役、￣は１フレーム過去であることを表わす。εは０＜ε≦１を満たす忘却係数であり、指数関数的な減衰の時定数を決定する。例えばε＝０.０１６とする。εが１に近づくほど現在の再生信号スペクトルＸ_ωと収音信号スペクトルＹ_ωに依存した（重み付けされた）それぞれの値になる。なお、式（１０）〜（１２）は従来から用いられている式である。また、周波数軸方向にも着目した式（１３）〜（１５）を用いてもよい。

Here, * represents a complex conjugate and ￣ represents one frame in the past. ε is a forgetting factor satisfying 0 <ε ≦ 1, and determines an exponential decay time constant. For example, ε = 0.016. As ε approaches 1, the values depend (weight) on the current reproduction signal spectrum X _ω and the collected sound signal spectrum Y _ω . In addition, Formula (10)-(12) is a formula used conventionally. Moreover, you may use Formula (13)-(15) which paid its attention also to the frequency-axis direction.

ここでＭ₁〜Ｍ₂は所定の周波数範囲を表わす。式（１３）〜（１５）は周波数軸方向に相関を取った後に時間軸方向の相関を取る形である。相関を取る順番は逆でもよい。また、式（１０）に替えて位相成分を考慮しない絶対値から求める式（１６）を用いてもよい。

Here, M _{1 to} M ₂ represent a predetermined frequency range. Expressions (13) to (15) are forms in which the correlation is taken in the time axis direction after the correlation is taken in the frequency axis direction. The order of correlation may be reversed. Further, instead of Expression (10), Expression (16) obtained from an absolute value that does not consider the phase component may be used.

The similarity coefficient calculation unit 12 calculates the respective values using the equations (10) to (12), and then calculates the similarity coefficient r _ω using the above equation (8) (step S12).

The echo suppression gain calculation unit 14 calculates the gain coefficient G _ω ^p shown in Expression (9) using the echo power estimated value | D _ω ^ | ² and the similarity coefficient r _ω as inputs (step S14). As is clear from Equation (9), the gain coefficient G _ω ^p becomes smaller as the similarity coefficient r _ω approaches 1. This is because the echo power adjustment means 14a provided in the echo power suppression gain calculator 14 adjusts the echo power estimated value | D _ω ^ | ² by multiplying it by the similarity coefficient r _ω .

  The configuration of the echo suppression gain calculation unit 14 will be described in detail with reference to FIG. The echo suppression gain calculation unit 14 includes an echo power adjusting unit 14a, a subtracting unit 14b, a dividing unit 14c, a register 14d that records a constant C that eliminates an echo cancellation residue, and a register 14e that records an enhancement coefficient α. Prepare.

The echo power adjustment means 14a receives the estimated echo power value | D _ω ^ | ² and the similarity coefficient r _ω as input, multiplies each value by the power of the enhancement coefficient α, and multiplies each value by a constant C. The echo power adjustment value is calculated by multiplication (step S14a in FIG. 4).
Subtracting means 14b inputs the echo power adjustment value and the collected signal spectrum Y _omega, subtracts the echo-power adjustment values to absolute values of sound collection signal spectrum Y _omega from the value raised to the power of the enhancement coefficient alpha (step S14b) .

ここで強調係数αは正の数であるとして例えば２とする。定数Ｃは正の数であるとして例えば１.５とする。強調係数αと、定数Ｃは、類似度係数ｒ_ωが通常１以下であることから設けられた値でありゲイン係数Ｇ_ω ^ｐを適当な値に調整するものである。強調係数α＝２とするとウィナーフィルターに近い式になる。 The dividing unit 14c divides the output signal of the subtracting unit 14b by a value obtained by raising the absolute value of the collected sound signal spectrum Y _{ω to} the power of the enhancement coefficient α, and outputs a gain coefficient G _ω ^p (step SS14c). That is, the echo suppression gain calculation unit 14 calculates Expression (17) and outputs the gain coefficient G _ω ^p .

Here, the enhancement coefficient α is assumed to be a positive number, for example, 2. The constant C is assumed to be a positive number, for example, 1.5. The enhancement coefficient α and the constant C are values provided because the similarity coefficient r _ω is usually 1 or less, and are used to adjust the gain coefficient G _ω ^p to an appropriate value. When the emphasis coefficient α = 2, the expression is close to a Wiener filter.

The gain coefficient G _ω ^p obtained as described above operates the echo canceller 10 so as to reduce the loss of the near-end speaker signal s (k). Therefore, it is possible to perform echo suppression with less musical noise generation, which is more robust against voice distortion than the conventional method.

  FIG. 5 shows a functional configuration example of the echo suppression gain calculation unit 50 of the present invention as a second embodiment. The operation flow is shown in FIG. The echo suppression gain calculation unit 50 is obtained by changing the calculation method of the echo suppression gain calculation unit 14 of the first embodiment, and includes a gain calculation unit 50a, a dissimilarity coefficient generation unit 50b, a multiplication unit 50c, and a constant C. And a register 14e in which the enhancement coefficient α is recorded.

The gain calculation means 50a receives the echo power estimated value | D _ω ^ | ² and the collected sound signal spectrum Y _ω as inputs, and raises each absolute value to the power of the enhancement coefficient α. Power has been collected sound signal spectrum | Y _omega | subtracts the power value of the echo power estimate from ^alpha, further subtracted value collected sound signal spectrum | Y _omega | calculating the gain by dividing the ^alpha (step S50a ).
Dissimilarity coefficient generation means 50b generates the dissimilarity coefficient by subtracting a similarity coefficient r _omega 1 as input a similarity coefficient r _omega (step S50b). Multiplication means 50c is the output gain of the gain calculation unit 50a, by multiplying the dissimilarity coefficient and the constant C outputs a gain coefficient G _omega ^p (step S50c). That is, the echo suppression gain calculation unit 50 calculates Expression (18) and outputs the gain coefficient G _ω ^p .

以上のようにして求めたゲイン係数Ｇ_ω ^ｐでも、従来法に比べて音声歪みに対して頑健なミュージカルノイズ発生の少ないエコー抑圧を行うことが可能になる。
〔シミュレーション結果〕
この発明のエコー抑圧ゲイン推定方法を、短時間スペクトル振幅エコー抑圧処理に適用して従来法と性能比較を行った。シミュレーション条件は、サンプリング周波数１６ｋＨｚ、周波数分析長２５６点、１/２オーバーラップ加算による周波数分析合成、エコー経路ｄ（ｋ）の残響時間は３００ｍｓの部屋とし、４０９６点で計算を打ち切りとした。

Even with the gain coefficient G _ω ^p determined as described above, it is possible to perform echo suppression that is more robust against voice distortion than the conventional method and generates less musical noise.
〔simulation result〕
The performance of the echo suppression gain estimation method of the present invention was compared with that of the conventional method by applying it to the short-time spectral amplitude echo suppression processing. The simulation conditions were a sampling frequency of 16 kHz, a frequency analysis length of 256 points, frequency analysis synthesis by 1/2 overlap addition, a reverberation time of the echo path d (k) was a room of 300 ms, and the calculation was terminated at 4096 points.

  The simulation result is shown in FIG. FIG. 7 (a) shows the echo signal in the state of only the echo signal (single talk) by a broken line, and the output signal e (k) at the time of the echo signal shows the conventional method by a dotted line and the method of the present invention by a solid line. . FIG. 7B shows the same signals in the double talk state. The horizontal axis represents time in seconds [S], and the vertical axis represents power in [dB].

  From FIG. 7A, it can be seen that both the conventional method and the method of the present invention show sufficient echo suppression performance of 20 dB or more. In the double talk state of FIG. 7B, a portion where the near-end speaker signal of the conventional method is lost by about 6 dB can be seen in 7 to 8 seconds. In contrast, it can be seen that the method of the present invention can reproduce the near-end speaker signal throughout.

As described above, by using the echo suppression gain estimation method of the present invention, it is possible to reduce the occurrence of musical noise while achieving high echo suppression performance.
In addition, the method and apparatus of this invention are not limited to the above-mentioned embodiment, In the range which does not deviate from the meaning of this invention, it can change suitably. Further, the processes described in the above method and apparatus are not only executed in time series according to the order of description, but also may be executed in parallel or individually as required by the processing capability of the apparatus that executes the processes. Good.

  Further, when the processing means in the above apparatus is realized by a computer, the processing contents of functions that each apparatus should have are described by a program. Then, by executing this program on the computer, the processing means in each apparatus is realized on the computer.

  The program describing the processing contents can be recorded on a computer-readable recording medium. As the computer-readable recording medium, for example, any recording medium such as a magnetic recording device, an optical disk, a magneto-optical recording medium, and a semiconductor memory may be used. Specifically, for example, as a magnetic recording device, a hard disk device, a flexible disk, a magnetic tape or the like, and as an optical disk, a DVD (Digital Versatile Disc), a DVD-RAM (Random Access Memory), a CD-ROM (Compact Disc Read Only). Memory), CD-R (Recordable) / RW (ReWritable), etc., magneto-optical recording medium, MO (Magneto Optical disc), etc., semiconductor memory, EEP-ROM (Electronically Erasable and Programmable-Read Only Memory), etc. Can be used.

The program is distributed by selling, transferring, or lending a portable recording medium such as a DVD or CD-ROM in which the program is recorded. Further, the program may be distributed by storing the program in a recording device of a server computer and transferring the program from the server computer to another computer via a network.
Each means may be configured by executing a predetermined program on a computer, or at least a part of these processing contents may be realized by hardware.

The figure which shows the function structural example of the echo cancellation apparatus 10 using the echo suppression gain estimation method of this invention. The figure which shows the operation | movement flow of the echo suppression gain estimation method of this invention. The figure which shows the function structural example of the echo suppression gain calculation part 14. FIG. The figure which shows the operation | movement flow of the echo suppression gain estimation method including the more detailed operation | movement flow of the echo suppression gain calculation part 14. FIG. The figure which shows the function structural example of the echo suppression gain calculation part 50. FIG. The figure which shows the operation | movement flow of the echo suppression gain estimation method including the operation | movement flow of the echo suppression gain calculation part 50. FIG. The figure which shows a simulation result. The figure which shows the function structural example of the conventional echo cancellation apparatus 80. FIG.

Claims (10)

A reproduction signal frequency analysis stage for converting the reproduction signal into a reproduction signal spectrum in the frequency domain;
A sound collection signal frequency analysis stage for converting the sound collection signal into a frequency-domain sound collection signal spectrum;
An echo power estimation step of calculating an echo power estimation value using the reproduction signal spectrum and the collected sound signal spectrum as inputs;
A similarity coefficient calculating step of calculating a similarity coefficient obtained by normalizing the inner product value of the reproduced signal spectrum and the collected sound signal spectrum by a product of the respective sizes of the reproduced signal spectrum and the collected sound signal spectrum;
Echo suppression gain that receives the sound collection signal spectrum, the similarity coefficient, and the echo power estimation value and calculates a gain coefficient for suppressing echo so that the gain coefficient becomes smaller as the similarity coefficient approaches 1 The calculation stage;
An echo suppression gain estimation method comprising: The echo suppression gain estimation method according to claim 1,
The echo suppression gain estimation method, wherein the echo suppression gain calculation step includes an echo power adjustment process for generating an echo power adjustment value obtained by multiplying the echo power estimation value by the similarity coefficient. The echo suppression gain estimation method according to claim 2,
The echo suppression gain calculation stage is
The above echo power adjustment process,
A subtraction process for subtracting the echo power adjustment value from the collected sound signal spectrum;
A division process of dividing the output signal of the subtraction process by the collected sound signal spectrum;
An echo suppression gain estimation method comprising: The echo gain suppression estimation method according to claim 1,
The echo suppression gain calculation stage is
A gain calculation process for calculating a gain from the collected sound signal spectrum and the echo power estimation value;
A dissimilarity coefficient generation process for generating a dissimilarity coefficient from the similarity coefficient;
A multiplication process for multiplying the gain by the dissimilarity coefficient;
An echo suppression gain estimation method comprising: A reproduction signal frequency analysis unit for converting the reproduction signal into a reproduction signal spectrum in the frequency domain;
A sound collecting signal frequency analysis unit for converting the sound collecting signal into a sound collecting signal spectrum in the frequency domain;
An echo power estimator for calculating an echo power estimated value by inputting the reproduction signal spectrum and the collected sound signal spectrum;
A similarity coefficient calculator that calculates a similarity coefficient obtained by normalizing the inner product value of the reproduced signal spectrum and the collected sound signal spectrum by a product of the respective sizes of the reproduced signal spectrum and the collected sound signal spectrum;
Echo suppression gain for calculating a gain coefficient for suppressing echoes by using the collected sound signal spectrum, the similarity coefficient, and the echo power estimation value as input so that the gain coefficient decreases as the similarity coefficient approaches 1. A calculation unit;
An echo canceller comprising: The echo canceller according to claim 5, wherein
The echo cancellation apparatus, wherein the echo suppression gain calculation unit includes echo power adjustment means for generating an echo power adjustment value obtained by multiplying the echo power estimated value by the similarity coefficient. The echo canceller according to claim 6, wherein
The echo suppression gain calculation unit includes the echo power adjustment unit,
Subtracting means for subtracting the echo power adjustment value from the collected sound signal spectrum;
Division means for dividing the output signal of the subtraction means by the collected sound signal spectrum;
An echo canceller characterized by comprising: The echo canceller according to claim 5, wherein
The echo suppression gain calculation unit includes gain calculation means for calculating a gain from the collected sound signal spectrum and the echo power estimated value;
Dissimilarity coefficient generating means for generating a dissimilarity coefficient from the similarity coefficient;
Multiplying means for multiplying the gain by the dissimilarity coefficient;
An echo canceller characterized by comprising:   An apparatus program for causing a computer to function as the echo canceling apparatus according to claim 5.   A computer-readable recording medium on which any of the apparatus programs according to claim 9 is recorded.

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