JP5087024B2 - Echo canceling apparatus, method and program - Google Patents

Description

  The present invention relates to an echo canceling apparatus for canceling an acoustic echo that causes a howling and an auditory disturbance, and a method and a program thereof, which are used in, for example, a communication conference system having an acoustic reproduction system.

  Echo suppression processing based on short-time spectral amplitude (STSA) estimation is based on the fact that the human auditory characteristics are insensitive to the phase and the statistical characteristics of the echo, and the amplitude of the echo in the frequency domain. This is achieved by subtracting the components. A conventional echo canceller 800 that suppresses echoes in the frequency domain is described in Non-Patent Document 1, for example.

FIG. 8 shows an example of the functional configuration of the echo canceller 800, and its operation will be described. The echo canceling apparatus 800 is input to the receiving end 1 and is a reproduction signal x that is converted into an acoustic signal by the speaker 2.
(K) and a collected sound signal y (k) in which an echo component influenced by an indoor impulse response (transfer function) (not shown) is superimposed on a reproduction signal x (k) converted into an acoustic signal output from the microphone 3. Are input signals. The output signal e (k) output to the transmitting end 4 of the echo canceller 800 is a signal in which the echo component of the collected sound signal y (k) is suppressed.

The echo cancellation apparatus 800 includes a first frequency analysis unit 81, a second frequency analysis unit 82, an acoustic coupling amount calculation unit 83, an echo power calculation unit 84, a gain calculation unit 85, an integration unit 86, and a frequency synthesis unit 87. The first frequency analysis unit 81 receives the reproduction signal x (k) and outputs a reproduction signal spectrum X _ω (i). The second frequency analysis unit 82 receives the collected sound signal y (k) and outputs the collected sound signal spectrum Y _ω (i). Here, k is a sample point number indicating a discrete time of a predetermined interval, and the reproduction signal x (k) and the sound collection signal y (k) are digital signals. In FIG. 8, an A / D converter that converts an analog signal input to the speaker 2 and an analog signal output from the microphone 3 into a digital signal is omitted.

In the reproduction signal spectrum X _ω (i) and the collected sound signal spectrum Y _ω (i), ω is a frequency value, which is a frequency number of the spectrum obtained at a predetermined frequency interval. I is a frame number. The time length of the frame is, for example, 16 ms when the sampling frequency is 16 kHz and the data amount of frequency analysis is 256 points.

The acoustic coupling amount calculation unit 83 receives the reproduction signal spectrum X _ω (i) and the collected sound signal spectrum Y _ω (i) as inputs, and outputs an estimated value | H _ω ^ (i) | ² of the acoustic coupling amount. The acoustic coupling amount is a value representing the acoustic magnitude of an echo path that goes from the speaker 2 to the microphone 3. The estimated value of the acoustic coupling amount | H _ω ^ (i) | ² is calculated by the equation (1).

Here, * is a conjugate complex number, and N is the number of added frames. For example, a value such as N = 500 is set. i takes an integer value of i = 0, 1,..., N−1.
Echo-power calculating unit 84, the reproduction signal spectrum X ω _(i) the acoustic coupling amount estimate ^{_{| H ω ^ (i) |}} 2 as input echo power estimate ^{_{| D ω ^ (i) |}} 2 of the formula Calculate in (2).

The gain calculation unit 85 receives the echo power estimated value | D _ω ^ (i) | ² and the collected sound signal spectrum Y _ω (i) as input, and calculates the gain coefficient G _ω (i) by the equation (3).

The gain coefficient G _ω (i) takes a real value between 0 and 1, and is small when the collected sound signal spectrum Y _ω (i) has many echo components, and large when there are many components other than the echo components. Value.
Integrating unit 86 outputs the sound collection signal spectrum Y ω _(i) the gain coefficient G ω _(i) integrating to the echo-canceled signal spectrum E _{ω (i).}
The frequency synthesizer 87 re-synthesizes and outputs the output signal e (k) in the time domain from the echo cancellation signal spectrum E _ω (i) corresponding to the frequency value ω.

C. Faller and C. Tournery, “Estimating the delay and coloration effect of the acoustic echo path for low complexity echo suppression,” Proc. IWAENC2005, pp.53-56, Oct. 2005

  In the echo canceller 800 that processes every finite frame, it is necessary to use a frame longer than the impulse response length of the echo path in order to estimate the acoustic coupling amount of the entire echo path. However, the impulse response length varies greatly depending on the acoustic environment of the room, and its value is generally in the range of 100 ms to 400 ms. On the other hand, the frame length is a value such as 16 ms as described above. Therefore, the impulse response length of the echo path is often larger than the frame length. Therefore, in the conventional echo canceller, an erroneous estimation of the acoustic coupling amount is likely to occur. As a result, the echo power could not be estimated accurately, which was one of the causes of the generation of musical noise.

  The present invention has been made in view of this point, and an object of the present invention is to provide an echo cancellation apparatus capable of estimating echo power with high accuracy regardless of the impulse response length of the echo path, and a method and program thereof.

The echo cancellation apparatus of the present invention includes a first frequency analysis unit, a second frequency analysis unit, an acoustic coupling amount calculation unit, an echo power calculation unit, a gain calculation unit, an integration unit, and a frequency synthesis unit. It has. The first frequency analysis unit outputs a reproduction signal spectrum obtained by frequency conversion of the reproduction signal. The second frequency analysis unit outputs a sound collection signal spectrum obtained by frequency-converting the sound collection signal. The acoustic coupling amount calculation unit multiplies the reproduction signal spectrum and the collected sound signal spectrum within a range of a predetermined number of frames N and divides it by a value obtained by adding the power of the predetermined number of frames of the reproduction signal spectrum. The first acoustic coupling amount estimated value, and the coupling calculated by shifting the reproduced signal spectrum to the past time m (m = 1 to M−1) with respect to the collected sound signal spectrum in the same manner as the first acoustic coupling amount estimated value. The first to M-th acoustic coupling amount estimation values obtained by squaring the second acoustic coupling amount estimation value to the M-th acoustic coupling amount estimation value and the first acoustic coupling amount estimation value to the M-th acoustic coupling amount estimation value, respectively. Output. The echo power calculation unit receives the reproduction signal spectrum and the first to Mth acoustic coupling amount estimation values as input, and multiplies the acoustic coupling amount estimation value of the current time frame by the power of the reproduction signal spectrum and the past time m. the sum of the corresponding values obtained by multiplying the power of the acoustic coupling amount estimating value and the reproduction signal spectrum of the past same time the value of the m in the range of (m = 1~M-1), as an echo power estimate Output. The gain calculation unit receives the collected sound signal spectrum and the echo power estimation value and outputs a gain coefficient. The integrating unit outputs an echo cancellation signal spectrum obtained by multiplying the collected sound signal spectrum by a gain coefficient. The frequency synthesizer frequency synthesizes the echo cancellation signal spectrum and outputs an output signal in the time domain.

  The echo canceller of the present invention obtains a coupling amount obtained by shifting the reproduction signal spectrum with respect to the collected sound signal spectrum in the past as an acoustic coupling amount estimation value. Therefore, it is possible to estimate the acoustic coupling amount with high accuracy regardless of the impulse response length of the echo path. That is, since the reproduction signal of a certain frame and the reproduction signal of other frames are statistically uncorrelated, the cross spectrum addition value of the reproduction signal of the past time and the sound collection signal of the frame of the current time is It is possible to extract the acoustic coupling amount of the echo path of the past frame from which the uncorrelated component is removed. Therefore, the echo path is obtained by summing the product of the acoustic coupling amount estimate value of the frame at the current time and the power of the reproduction signal spectrum and the product of the past acoustic coupling amount estimate value and the reproduction signal spectrum at the same time. Even when the impulse response length is longer than the frame, the echo power can be estimated with high accuracy.

The figure which shows the function structural example of the echo cancellation apparatus 100 of this invention. The figure which shows the function structural example of the acoustic coupling amount calculation part 13. FIG. The figure which shows the operation | movement flow of the acoustic coupling amount calculation part 13. FIG. The figure which shows calculation of Formula (5). The figure which shows the function structure of the echo power calculation part. The figure which shows the operation | movement flow of the echo power calculation part 14. FIG. The figure which shows an experimental result. The figure which shows the function structural example of the conventional echo cancellation apparatus 800.

  Embodiments of the present invention will be described below with reference to the drawings. The same components in the drawings are denoted by the same reference numerals, and the description thereof is omitted.

  FIG. 1 shows a functional configuration example of an echo canceling apparatus 100 of the present invention. The echo cancellation apparatus 100 includes a first frequency analysis unit 81, a second frequency analysis unit 82, an acoustic coupling amount calculation unit 13, an echo power calculation unit 14, a gain calculation unit 85, an integration unit 86, and a frequency synthesis unit 87. . The echo canceling apparatus 100 is realized by reading a predetermined program into a computer composed of, for example, a ROM, a RAM, a CPU, etc., and executing the program by the CPU. In the echo canceller 100, the acoustic coupling amount calculator 13 and the echo power calculator 14 are new, and other configurations are the same as those of the conventional echo canceller 800. About the same part as the past, the same reference numerals are used to simplify the description.

The first frequency analysis unit 81 outputs a reproduction signal spectrum X _ω (i) obtained by frequency conversion of the reproduction signal x (k). The second frequency analysis unit 82 outputs a sound collection signal spectrum Y _ω (i) obtained by frequency-converting the sound collection signal y (k). The acoustic coupling amount calculator 13 multiplies the reproduction signal spectrum X _ω (i) and the collected sound signal spectrum Y _ω (i) by multiplying them within a range of a predetermined number of frames N, and adds a predetermined number N of frames of the reproduction signal spectrum. of the square of the divided amounts of bound antibody power by a value obtained by adding the a first acoustic coupling estimation value, collected sound signal spectrum Y _omega reproduced signal spectrum X _omega (i) to the (i), a past time m ( m = 1 to M−1), and a value calculated in the same manner as the first acoustic coupling amount estimated value is set as a second acoustic coupling amount estimated value to an Mth acoustic coupling amount estimated value. From the first acoustic coupling amount estimated value, The Mth acoustic coupling amount estimated value is output as the first to Mth acoustic coupling amount estimated values | _Hω ^ (i, m) | ² .

The echo power calculation unit 14 receives the reproduction signal spectrum X _ω (i) and the first to Mth acoustic coupling amount estimation values as inputs, and the first to Mth acoustic coupling amount estimation values | H _ω ^ (i, m ) | ² is multiplied by the power of the reproduction signal spectrum X _ω (i−1) corresponding to the value of m (m = 0 to M−1), and the echo power estimated value | D _ω ^ (I) Output as | ² . The gain calculation unit receives the collected sound signal spectrum Y _ω (i) and the echo power estimated value | D _ω ^ (•) | ² as input, and outputs a gain coefficient G _ω (i). The accumulator 86 outputs an echo cancellation signal spectrum E _ω (i) obtained by multiplying the collected sound signal spectrum Y _ω (i) by a gain coefficient G _ω (i). The frequency synthesizer 87 frequency synthesizes the echo cancellation signal spectrum E _ω (i) and outputs a time domain output signal e (k).

As described above, the echo canceling apparatus 100 obtains the coupling amount obtained by shifting the reproduction signal spectrum with respect to the collected sound signal spectrum in the past as the first to Mth acoustic coupling amount estimation values. Then, the sum of the values obtained by multiplying each of the acoustic coupling amount estimated values by the power of the reproduction signal spectrum X _ω (i) corresponding to the value of m (m = 0 to M−1) is used as the echo power estimated value. Output. Therefore, even when the impulse response length of the echo path is longer than the frame, the echo power can be estimated with high accuracy. Hereinafter, the acoustic coupling amount calculator 13 and the echo power calculator 14 which are new parts of the echo canceller 100 will be described in detail.

[Acoustic coupling amount calculation part]
FIG. 2 shows a functional configuration example of the acoustic coupling amount calculation unit 13. The operation flow is shown in FIG. The acoustic coupling amount calculation unit 13 includes a cross spectrum addition unit 130, a power spectrum addition unit 131, and a division / square unit 132, and a sound collection signal spectrum Y _ω (i) and a reproduction signal spectrum X _ω (i ) As an input, the estimated value | H _ω ^ (i, m) | ² of the acoustic coupling amount is calculated by Expression (4).

Here, m is a value that takes an integer value of m = 0, 1,..., M−1, and the collected sound signal spectrum Y
_This represents the number of frames by which the reproduction signal spectrum X _ω (i−j−m) is shifted to a past time with respect to _ω (i−j).
N (m) is a predetermined number of frames and represents a frame width for obtaining an estimated value of the acoustic coupling amount. C (m) is an adjustment constant, for example, C (m) = 1.

The cross spectrum addition unit 130 calculates the numerator on the right side of the equation (5) (step S1).
30). The calculation is performed by using the reproduction signal spectrum X _ω (ij) in the frequency domain and the collected sound signal spectrum Y _ω (ij) as inputs, and the reproduction signal spectrum X _ω (·) (· means i-1 and i-2, etc.) and the collected sound signal spectrum Y _omega (·) multiplied by the range of a predetermined number of frames N (m) seeking cross spectrum (step S130a), the cross-spectral This is a calculation for adding the cross spectrum addition value C _RS (m) by addition (step S130b). In this calculation, the reproduction signal spectrum X _ω (•) with respect to the collected sound signal spectrum Y _ω (•) is shifted in the range of m = 0, 1,..., M−1.

The power spectrum addition unit 131 calculates the denominator of Equation (5) (step S131). The calculation is performed for each of the reproduction signal spectra X _ω (i) to X _ω (i−j) in the range of a predetermined number of frames N (m) (j = N (m) −1) from the current time frame. The power is obtained (step S131a), and the total power P _S (m) obtained by adding them is calculated (step S131b). This calculation is also performed by shifting the reproduction signal spectrum X _ω (·) within a range of m = 0, 1,..., M−1.
The division / square unit 132 calculates first to Mth acoustic coupling amount estimation values obtained by squaring a value obtained by dividing the cross spectrum addition value C _RS (m) by the total power value P _S (m) (step S132). ).

The above calculation is shown in FIG. FIG. 4 shows an example where N = 4 and M = 3. When m = 0, the first acoustic coupling amount is calculated. In this case, the cross spectrum of the numerator of Equation (5) is the same as the reproduction signal spectrum X _ω (•) of the same time from the current time (i) to the time (i-3) four frames past. This is a value obtained by multiplying the sound signal spectrum Y _ω (•) and summing the respective multiplication values. The denominator is the total power of the reproduction signal spectrum X _ω (•) at each time from the current time (i) to (i-3).

When m = 1, the second acoustic coupling amount is calculated. In this case, the cross spectrum of the numerator is obtained by multiplying the sound collection signal spectrum Y _ω (i) at the current time by the reproduction signal spectrum X _ω (i−1) at the time one frame past, and thereafter the time (i− It is repeated until the sound collection signal spectrum Y _ω (i-3) of 3) is multiplied by the reproduction signal spectrum X _ω (i-4) of time (i-4), and the respective multiplication values are summed. The denominator in the case of m = 1 is the total power of the reproduction signal spectrum X _ω (•) at each time from time (i-1) to (i-4).

When m = 2, the third acoustic coupling amount is calculated. In this case, the sound collection signal spectrum Y _ω (i) is multiplied by the reproduction signal spectrum X _ω (i−2) at a time two frames past, and the same calculation is performed thereafter.

The acoustic coupling amount calculation unit 100 thus calculates the sum of the cross spectrum obtained by multiplying the collected signal spectrum Y _ω (i) at the current time by the reproduction signal spectrum X _ω (i−j−m) at the past time. Since the estimated value of the acoustic coupling amount is obtained, the acoustic coupling amount of the echo path at the past time can be extracted. As a result, it is possible to estimate the acoustic coupling amount of the entire echo path with high accuracy.

The adjustment constant C (m) is not particularly described as C (m) = 1, but may be set to a different value depending on m. For example, if m is large, the past frame time becomes a calculation target, so that the SN ratio is relatively lower than the acoustic coupling amount when m is small. Therefore, when m is large, for example, C (m) may be decreased. That is, an adjustment coefficient multiplication step (step S133) for reducing the past weight may be provided.

  Similarly, since the SN ratio of the past frame time decreases, the predetermined number of frames N (m) may be changed depending on the value of m. For example, if m is large, N (m) is also large. By doing so, since the cross spectrum addition value and the power value are further averaged, an improvement in accuracy can be expected.

[Echo power calculator]
FIG. 5 shows a functional configuration example of the echo power calculator 14. The operation flow is shown in FIG. The echo power estimation unit 14 includes a reproduction signal spectrum power calculation unit 140, a reproduction signal power recording unit 141, and a multiplication / accumulation unit 142. The reproduction signal power spectrum power calculation unit 140 squares the input reproduction signal spectrum X _ω (·) to obtain the reproduction signal spectrum power | X _ω (·) | ² (step S140). The reproduction signal spectrum power | X _ω (·) | ² is recorded in the reproduction signal spectrum power recording unit 141. The multiplication / accumulation unit 142 calculates the acoustic coupling amount estimated value | H _ω ^ (i, m) | ² and the past reproduction signal of m = 0 to M−1 from the present recorded in the reproduction signal spectrum power recording unit 141. Using the spectral power as an input, the echo power estimated value | D _ω ^ (·) | ² is calculated by Expression (6) (step S 142).

Thus, the echo power calculation unit 14 calculates the acoustic coupling amount estimated value | H _ω ^ (i, 0) | ² of the current time frame (i) and the reproduction signal spectrum power | Xω (i−0) | ² . The estimated value of the acoustic coupling amount | H _ω ^ (i, m) | ² at the same time within the range of the multiplication value and the past time m (m = 1 to M−1) and the power of the reproduction signal spectrum | Xω (I−m) | The multiplication value of ² is summed to obtain the echo power. Therefore, even when the impulse response length of the echo path is longer than the frame length, the echo power can be estimated with high accuracy.

〔Experimental result〕
For the purpose of confirming the effectiveness of the echo canceling apparatus 100 of the present invention, a performance comparison experiment between the conventional method and the STSA echo suppression processing was performed. The arrangement of the speakers and microphones is recommended by ITU-T Recommendation P.27. 34. The reverberation time is about 300 ms, the sampling frequency is 16 kHz, and the frequency band is 100 Hz to 7 kHz. In addition, the echo power estimation value of the conventional method is adjusted with a certain margin so that the echo suppression amount in the single talk state from the far-end speaker is almost equal.

  For the evaluation of the echo suppression amount, ERLE (Echo Return Lose Enhancement) which is a performance index of the acoustic echo canceller was used. The ERLE of this invention and the conventional system were 25.35 dB and 25.44 dB, respectively. The transmission distortion was evaluated by the cepstrum distance. The cepstrum distance is a distance (distortion) between a target signal (near-end speaker signal) and an output signal (signal after echo suppression). FIG. 7 shows a comparison during simultaneous calls. The horizontal axis of FIG. 7 is time [second], and the vertical axis is the cepstrum distance. The solid line is the present invention, and the broken line is the conventional method. As clearly shown after 0.3 seconds and 3.5 seconds, the present invention can reduce transmission distortion during simultaneous calls.

  The echo canceling apparatus and method of the present invention described above are not limited to the above-described embodiment, and can be appropriately changed without departing from the spirit of the present invention. For example, the processes described in the above-described apparatus and method are not only executed in time series in the order described, but are also executed in parallel or individually as required by the processing capability of the apparatus that executes the processes. Also good.

  When the processing means in the above apparatus is realized by a computer, the processing contents of the 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), CD-ROM (Compact Disc Read Only Memory), CD-R
(Recordable) / RW (ReWritable) or the like can be used as a magneto-optical recording medium, MO (Magneto Optical disc) or the like as a semiconductor memory, and flash memory or the like as a semiconductor memory.

  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.

Claims (7)

A first frequency analyzer that outputs a reproduction signal spectrum signal obtained by frequency conversion of the reproduction signal;
A second frequency analysis unit that outputs a collected sound signal spectrum obtained by frequency-converting the collected sound signal;
A value obtained by multiplying the reproduced signal spectrum and the collected sound signal spectrum of frames at the same time within a range of a predetermined number of frames N and adding the reproduced signal spectrum signal and the collected sound signal spectrum signal as inputs is the reproduced signal spectrum. The square of the absolute value of the coupling amount divided by the value obtained by adding the powers of the predetermined number of frames is defined as the first acoustic coupling amount estimated value, and the reproduced signal spectrum with respect to the collected sound signal spectrum is expressed as a past time m ( m = 1 to M−1), and a value calculated in the same manner as the first acoustic coupling amount estimation value is set as a second acoustic coupling amount estimation value to an Mth acoustic coupling amount estimation value, and the first acoustic coupling amount estimation is performed. An acoustic coupling amount calculator that outputs an estimated value of the Mth acoustic coupling amount from each value;
Using the reproduction signal spectrum and the first to Mth acoustic coupling amount estimation values as inputs, a multiplication value of the acoustic coupling amount estimation value of the current time frame and the reproduction signal spectrum power, and the past time m (m = 1). the sum of the corresponding values obtained by multiplying the power of the acoustic coupling amount estimating value and the reproduction signal spectrum of the past same time the value of the m in the range of ~M-1), the echo-power output as the echo power estimate A calculation unit;
A gain calculator that outputs the gain coefficient with the collected sound signal spectrum and the echo power estimation value as inputs;
An accumulator for outputting an echo cancellation signal spectrum obtained by multiplying the collected sound signal spectrum by the gain coefficient;
A frequency synthesizer that synthesizes the frequency of the echo cancellation signal spectrum and outputs an output signal in the time domain;
An echo canceller comprising: The echo canceller according to claim 1,
The acoustic coupling amount calculation unit multiplies each of the first to Mth acoustic coupling amount estimation values by an adjustment constant, and the adjustment constant is different depending on the value of m indicating the past time. Echo canceling device. In the echo canceller according to claim 1 or 2,
The acoustic coupling amount calculation unit sets the predetermined number of frames N to a value that increases when the value of m indicating the past time is large. A first frequency analysis process in which a first frequency analysis unit outputs a reproduction spectrum signal obtained by frequency-converting the reproduction signal;
A second frequency analysis process in which the second frequency analysis unit outputs a collected sound signal spectrum obtained by frequency-converting the collected sound signal;
The acoustic coupling amount calculation unit receives the reproduced signal spectrum signal and the collected sound signal spectrum signal as inputs, multiplies the reproduced signal spectrum and the collected sound signal spectrum of frames at the same time within a range of a predetermined number of frames N, and adds them. The amount of coupling obtained by dividing the value by the value obtained by adding the power of the predetermined number of frames of the reproduction signal spectrum is used as a first acoustic coupling amount estimation value, and the reproduction signal spectrum with respect to the sound collection signal spectrum A coupling amount calculated in the same manner as the first acoustic coupling amount estimation value by shifting to m (m = 1 to M−1) is set as a second acoustic coupling amount estimation value to an Mth acoustic coupling amount estimation value, and the first acoustic coupling amount is calculated. An acoustic coupling amount calculation process for outputting first to Mth acoustic coupling amount estimation values obtained by squaring the coupling amount estimation value to the Mth acoustic coupling amount estimation value, respectively;
The echo power calculation unit receives the reproduction signal spectrum and the first to Mth acoustic coupling amount estimation values as input, and multiplies the acoustic coupling amount estimation value of the current time frame and the reproduction signal spectrum power, and the past Echo power estimation is the sum of the past acoustic coupling amount estimated value corresponding to the value of m within the range of time m (m = 1 to M−1) and the value obtained by multiplying the power of the reproduction signal spectrum. Echo power calculation process to output as a value,
A gain calculation process in which a gain calculation unit outputs a gain coefficient with the collected sound signal spectrum and the echo power estimation value as inputs;
An integration unit that outputs an echo cancellation signal spectrum obtained by multiplying the collected sound signal spectrum by the gain coefficient; and
A frequency synthesizing unit that synthesizes the frequency of the echo cancellation signal spectrum and outputs an output signal in the time domain;
Echo cancellation method including In the echo cancellation method according to claim 4,
The acoustic coupling amount calculation process includes an adjustment constant multiplication step in which each of the first to Mth acoustic coupling amount estimation values is multiplied by an adjustment constant, and the adjustment constant is a value of m indicating the past time. An echo cancellation method characterized in that the value varies depending on the value. In the echo cancellation method according to claim 4 or 5,
The step of obtaining the value obtained by multiplying the sum of the reproduced signal spectrum and the collected sound signal spectrum of the frames at the same time in the acoustic coupling amount calculation process within a range of a predetermined number of frames N includes: An echo canceling method characterized in that if the value of m indicating the past time is large, the value becomes larger.   An apparatus program for causing a computer to function as the echo canceling apparatus according to claim 1.

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