JP7373947B2 - Acoustic echo cancellation device, acoustic echo cancellation method and acoustic echo cancellation program - Google Patents

Description

The present disclosure relates to an acoustic echo canceling device, an acoustic echo canceling method, and an acoustic echo canceling program that cancel an acoustic echo component of an input signal output from a microphone.

Conventionally, there has been a loudspeaker type two-way communication system using a microphone and a speaker. In such a loudspeaker type two-way communication system, the voice spoken by the speaker on the transmitting side is input to the microphone on the transmitting side, and is transmitted as a transmission signal to the device on the receiving side via a communication line. Played on the receiver's speaker. The sound reproduced by the speaker on the receiving side propagates through the space on the receiving side, is input to the microphone on the receiving side, and is transmitted to the transmitting side. At this time, the speaker on the transmitting side reproduces the voice that has been uttered after the time that it passed through the communication line and the time that it propagated through the space on the receiving side. In this way, the sound that propagates between the speaker on the receiver side and the microphone is called an acoustic echo, which leads to deterioration of the quality of the call.

Therefore, in amplified two-way communication systems, echo cancellers are used to suppress acoustic echoes.

Furthermore, in recent years, in order to provide a more natural communication environment, amplified two-way communication systems using a plurality of microphones have been developed (for example, see Patent Document 1).

Patent No. 5826712 specification

However, with the above-mentioned conventional technology, it is difficult to maintain communication performance and reduce the amount of calculation required to remove acoustic echoes, and further improvements are needed.

The present disclosure has been made to solve the above problems, and provides an acoustic echo canceling device and an acoustic echo canceling device that can maintain call performance and reduce the amount of calculation for removing acoustic echoes. It is an object of the present invention to provide a method and an acoustic echo cancellation program.

An acoustic echo canceling device according to an aspect of the present disclosure uses input signals obtained from at least two microphones and a reproduction signal output to a speaker, and uses an input signal that indicates a component of the reproduction signal included in the input signal. a first echo canceller that generates one pseudo echo signal; at least one input signal output from the at least two microphones; and the first pseudo echo signal generated by the first echo canceller. to generate a second pseudo echo signal indicating a component of the first pseudo echo signal included in the at least one input signal, and using the generated second pseudo echo signal to a second echo canceller that cancels an acoustic echo component of the signal.

According to the present disclosure, it is possible to maintain communication performance and reduce the amount of calculation for removing acoustic echoes.

1 is a diagram illustrating a configuration of a communication device according to Embodiment 1 of the present disclosure. FIG. It is a flowchart for explaining operation of the acoustic echo cancellation device in Embodiment 1 of this indication. FIG. 3 is a diagram illustrating the configuration of a telephone communication device in Modification 1 of Embodiment 1 of the present disclosure. FIG. 3 is a diagram illustrating the configuration of a telephone communication device in Embodiment 2 of the present disclosure. It is a flowchart for explaining operation of the acoustic echo cancellation device in Embodiment 2 of this indication. FIG. 7 is a diagram illustrating a configuration of a telephone communication device in a modification of Embodiment 2 of the present disclosure. FIG. 3 is a diagram showing the configuration of a telephone communication device in Embodiment 3 of the present disclosure. It is a flow chart for explaining operation of an acoustic echo cancellation device in Embodiment 3 of this indication. FIG. 7 is a diagram showing the configuration of a telephone communication device in a modification of Embodiment 3 of the present disclosure. FIG. 7 is a diagram illustrating the configuration of a communication device in a second modification of the first embodiment of the present disclosure.

(Findings that formed the basis of this disclosure)
In a public address communication system that uses multiple microphones, an echo canceller is required for each microphone, so the number of echo cancellers increases in accordance with the number of microphones, and the amount of calculation for the multiple echo cancellers increases.

The conventional multi-channel echo canceling device described above includes the same number of echo replica generating units as microphones, and each echo replica generating unit has the same configuration. Therefore, as the number of microphones increases, the number of echo replica generators also increases, and the amount of calculations required to remove acoustic echoes may also increase.

In addition, in the conventional multi-channel echo cancellation device described above, by limiting the echo replica generation process and the adaptive filter coefficient update process to an effective wave number region, the multi-channel loudspeaker system consisting of a large number of speakers and microphones is The overall amount of computation is reduced.

However, in the conventional multi-channel echo canceling device, since the wave number region of the echo replica generating section is limited, a wave number region that is not learned occurs, and the limitation of the wave number region may cause deterioration of speech performance.

In order to solve the above problems, an acoustic echo canceling device according to one aspect of the present disclosure uses input signals obtained from at least two microphones and a reproduced signal output to a speaker. a first echo canceller that generates a first pseudo-echo signal representing a component of the reproduced signal to be reproduced; at least one input signal output from the at least two microphones; using the first pseudo echo signal to generate a second pseudo echo signal indicating a component of the first pseudo echo signal included in the at least one input signal, and the generated second pseudo echo. a second echo canceller that uses the signal to cancel an acoustic echo component of the at least one input signal.

According to this configuration, since the second pseudo echo signal is generated using the already generated first pseudo echo signal, the filter length of the adaptive filter used when generating the second pseudo echo signal is (tap length) can be shortened, communication performance can be maintained, and the amount of calculation for removing acoustic echo can be reduced.

The acoustic echo canceling device described above further includes a delay unit that delays at least one input signal output from the at least two microphones, and the second echo canceller is configured to delay the at least one input signal output from the at least two microphones. and the first pseudo echo signal generated by the first echo canceller. A pseudo echo signal may be generated, and the generated second pseudo echo signal may be used to cancel the delayed acoustic echo component of the at least one input signal.

According to this configuration, by delaying at least one input signal input to the second echo canceller, the time difference between the first pseudo echo signal generated by the first echo canceler and the at least one input signal is reduced. Therefore, the second pseudo echo signal can be reliably generated.

Further, in the above acoustic echo canceling device, the at least two microphones include a first microphone that outputs the first input signal and a second microphone that outputs the second input signal, and the delay unit includes a first delay section that delays the first input signal and a second delay section that delays the second input signal, and the first input signal and the second input signal The first echo canceller further includes an adding section that adds up a component of the reproduced signal included in the added signal, using the added signal from the adding section and the reproduced signal. generating a pseudo-echo signal, the second echo canceller using the delayed first input signal and the first pseudo-echo signal generated by the first echo canceller; generate a third pseudo echo signal indicating a component of the first pseudo echo signal included in the first input signal, and use the generated third pseudo echo signal to generate the delayed first echo signal; using a third echo canceller that cancels an acoustic echo component of an input signal, the delayed second input signal, and the first pseudo echo signal generated by the first echo canceller, A fourth pseudo echo signal indicating a component of the first pseudo echo signal included in the delayed second input signal is generated, and using the generated fourth pseudo echo signal, the delayed and a fourth echo canceller that cancels an acoustic echo component of the second input signal.

According to this configuration, by delaying the first input signal input to the third echo canceller and delaying the second input signal input to the fourth echo canceller, the signal generated by the first echo canceller is The time difference between the first pseudo echo signal and the first input signal is eliminated, and the time difference between the first pseudo echo signal and the second input signal is also eliminated, ensuring that the third pseudo echo signal and the fourth can generate a pseudo echo signal.

Further, in the above acoustic echo canceling device, the at least two microphones include a first microphone that outputs a first input signal and a second microphone that outputs a second input signal, and the first microphone and the second input signal, and the first echo canceller uses the addition signal from the addition section and the reproduced signal to add the input signal included in the addition signal. The second echo canceller generates the first pseudo echo signal representing a component of the reproduced signal, and the second echo canceller receives the first input signal and the first pseudo echo signal generated by the first echo canceller. A third pseudo echo signal indicating a component of the first pseudo echo signal included in the first input signal is generated using the signal, and the generated third pseudo echo signal is used to generate the third pseudo echo signal. a third echo canceller that cancels an acoustic echo component of the first input signal, the second input signal, and the first pseudo echo signal generated by the first echo canceller; generate a fourth pseudo echo signal indicating a component of the first pseudo echo signal included in the second input signal, and use the generated fourth pseudo echo signal to detect the acoustic echo component of the second input signal. and a fourth echo canceller that cancels the echo canceller.

According to this configuration, the at least two microphones are arranged at different positions. Therefore, the waveform of the reflected wave (echo signal) input as an acoustic echo differs from microphone to microphone. If the phase of the echo signal is opposite to the input signal, which is the speaker's voice, the echo signal is added to the input signal, causing the input signal to disappear and canceling the acoustic echo of the input signal. becomes difficult. However, since the first input signal and the second input signal from at least two microphones are added, it is possible to reduce the effect of signal loss due to acoustic echo interference.

Further, in the above acoustic echo canceling device, the at least two microphones include a first microphone that outputs a first input signal and a second microphone that outputs a second input signal, and the first microphone The echo canceller uses the first input signal and the reproduced signal to generate the first pseudo echo signal indicating a component of the reproduced signal included in the first input signal, and a first pseudo-echo signal to cancel an acoustic echo component of the first input signal; and a first pseudo echo signal to generate a second pseudo echo signal indicating a component of the first pseudo echo signal included in the second input signal, and generate the second pseudo echo signal. may be used to cancel the acoustic echo component of the second input signal.

According to this configuration, since the second pseudo echo signal is generated using the already generated first pseudo echo signal, the filter length of the adaptive filter used when generating the second pseudo echo signal is (tap length) can be shortened, communication performance can be maintained, and the amount of calculation for removing acoustic echo can be reduced.

Further, in the above acoustic echo canceling device, the at least two microphones include a first microphone that outputs a first input signal and a second microphone that outputs a second input signal, and the first microphone The echo canceller includes: a first calculation unit that calculates a first error signal indicating an error between the first input signal and the first pseudo echo signal; a second calculation unit that calculates a second error signal indicating an error with the pseudo echo signal; and an averaging processing unit that averages an added signal obtained by adding the first error signal and the second error signal. , a generation unit that uses the average signal from the average processing unit and the reproduced signal to generate the first pseudo echo signal indicating a component of the reproduced signal included in the average signal, The second echo canceller uses the first input signal and the first pseudo echo signal generated by the first echo canceller to cancel the first pseudo echo signal included in the first input signal. a third echo canceller that generates a third pseudo echo signal representing a component of an echo signal and cancels an acoustic echo component of the first input signal using the generated third pseudo echo signal; a fourth signal representing a component of the first pseudo echo signal included in the second input signal using the second input signal and the first pseudo echo signal generated by the first echo canceller; and a fourth echo canceller that generates a pseudo echo signal of and cancels an acoustic echo component of the second input signal using the generated fourth pseudo echo signal.

According to this configuration, the at least two microphones are arranged at different positions. Therefore, the waveform of the reflected wave (echo signal) input as an acoustic echo differs from microphone to microphone. If the phase of the echo signal is opposite to the input signal, which is the speaker's voice, the echo signal is added to the input signal, causing the input signal to disappear and canceling the acoustic echo of the input signal. becomes difficult. However, since the respective error signals of the first input signal and the second input signal from at least two microphones are added and averaged, it is possible to reduce the influence of signal dropout due to acoustic echo interference.

Further, in the above acoustic echo canceling device, a first converter converts the input signal in the time domain to an input signal in the frequency domain, and a second converter converts the reproduced signal in the time domain to a reproduced signal in the frequency domain. a transformer, a third transformer that transforms the at least one input signal in the time domain into at least one input signal in the frequency domain; It may further include a fourth converter that converts into an echo signal.

According to this configuration, the first echo canceller and the second echo canceller can generate the first pseudo echo signal and the second pseudo echo signal using a frequency domain adaptive algorithm, and the convolution operation is performed using a frequency domain adaptive algorithm. Since it can be executed by multiplication, the amount of calculation can be further reduced.

Furthermore, in the acoustic echo canceling device described above, the filter length of the second echo canceller may be shorter than the filter length of the first echo canceller.

According to this configuration, it is possible to reduce the amount of calculation for removing acoustic echo in the second echo canceller.

Furthermore, in the acoustic echo canceling device described above, the first echo canceller may generate the first pseudo echo signal for a microphone located closest to the speaker.

According to this configuration, the first pseudo echo signal indicating the component of the reproduced signal included in the input signal is generated using the input signal output from the microphone located closest to the speaker and the reproduced signal. Since the second pseudo echo signal is generated using the first pseudo echo signal, the filter length (tap length) of the adaptive filter used to generate the second pseudo echo signal can be shortened. .

An acoustic echo canceling method according to another aspect of the present disclosure is an acoustic echo canceling method in an acoustic echo canceling device that cancels an acoustic echo component of an input signal output from a microphone, the method comprising: inputs obtained from the at least two microphones; A first pseudo echo signal indicating a component of the reproduced signal included in the input signal is generated using the signal and a reproduced signal outputted to a speaker, and a first pseudo echo signal indicating a component of the reproduced signal included in the input signal is generated, a second pseudo echo signal representing a component of the first pseudo echo signal included in the at least one input signal using an input signal and the first pseudo echo signal generated by the first echo canceller; An echo signal is generated, and the generated second pseudo-echo signal is used to cancel an acoustic echo component of the at least one input signal.

According to this configuration, since the second pseudo echo signal is generated using the already generated first pseudo echo signal, the filter length of the adaptive filter used when generating the second pseudo echo signal is (tap length) can be shortened, communication performance can be maintained, and the amount of calculation for removing acoustic echo can be reduced.

An acoustic echo cancellation program according to another aspect of the present disclosure uses input signals obtained from at least two microphones and a reproduction signal output to a speaker to indicate the components of the reproduction signal included in the input signal. a first echo canceller that generates a first pseudo echo signal; at least one input signal output from the at least two microphones; and the first pseudo echo signal generated by the first echo canceller. to generate a second pseudo echo signal indicating a component of the first pseudo echo signal included in the at least one input signal, and using the generated second pseudo echo signal to The computer functions as a second echo canceller that cancels the acoustic echo component of the input signal.

According to this configuration, since the second pseudo echo signal is generated using the already generated first pseudo echo signal, the filter length of the adaptive filter used when generating the second pseudo echo signal is (tap length) can be shortened, communication performance can be maintained, and the amount of calculation for removing acoustic echo can be reduced.

Embodiments of the present disclosure will be described below with reference to the accompanying drawings. Note that the following embodiments are examples that embody the present disclosure, and do not limit the technical scope of the present disclosure.

(Embodiment 1)
FIG. 1 is a diagram illustrating the configuration of a communication device according to Embodiment 1 of the present disclosure. The telephone device is used in a loudspeaker hands-free telephone system, a loudspeaker two-way communication conference system, an intercom system, etc. installed in a car or the like.

The telephone device shown in FIG. 1 includes an acoustic echo canceling device 1, a first microphone 11, a second microphone 12, an input terminal 14, a speaker 15, a first output terminal 20, and a second output terminal 21.

The first microphone 11 and the second microphone 12 are placed in a space where a speaker is present, and collect the voice of the speaker. The first microphone 11 outputs a first input signal indicating the collected sound to the acoustic echo canceling device 1 . The second microphone 12 outputs a second input signal indicating the collected sound to the acoustic echo canceling device 1 .

The input terminal 14 outputs a reproduced signal received from a receiving side communication device (not shown) to the acoustic echo canceling device 1 and the speaker 15.

The speaker 15 outputs the input reproduction signal to the outside. Here, when the sound output from the speaker 15 is picked up by the first microphone 11 and the second microphone 12, the sound uttered by the speaker on the receiving side is played back from the speaker on the receiving side with a delay. This causes a so-called acoustic echo to occur. Therefore, the acoustic echo canceling device 1 cancels the acoustic echo components of the first input signal and the second input signal output from the first microphone 11 and the second microphone 12.

The first output terminal 20 outputs the first input signal whose acoustic echo component has been canceled by the acoustic echo canceling device 1 . The second output terminal 21 outputs the second input signal whose acoustic echo component has been canceled by the acoustic echo canceling device 1 .

Note that the input terminal 14, the first output terminal 20, and the second output terminal 21 are connected to a communication section (not shown). The communication unit transmits a first input signal and a second input signal to a receiving side communication device (not shown) via the network, and also receives a reproduction signal from the receiving side communication device (not shown) via the network. receive. The network is, for example, the Internet.

The acoustic echo canceling device 1 includes an adding section 13, a first echo canceller 16, and a second echo canceller 17.

The adder 13 adds the first input signal from the first microphone 11 and the second input signal from the second microphone 12.

The first echo canceller 16 uses the input signals obtained from at least two microphones and the reproduced signal output to the speaker to generate a first pseudo echo signal indicating a component of the reproduced signal included in the input signal. do.

In the first embodiment, the input signals obtained from at least two microphones are the summed signals obtained by adding the first input signal from the first microphone 11 and the second input signal from the second microphone 12. be. That is, the first echo canceller 16 uses the addition signal from the addition section 13 and the reproduction signal to generate a first pseudo echo signal indicating the component of the reproduction signal included in the addition signal.

The first echo canceller 16 includes an adaptive filter 161 and an error calculation section 162.

The adaptive filter 161 generates a first pseudo echo signal indicating the component of the reproduced signal included in the added signal by convolving the filter coefficient and the reproduced signal.

The error calculation unit 162 calculates an error signal between the addition signal from the addition unit 13 and the first pseudo echo signal from the adaptive filter 161, and outputs the calculated error signal to the adaptive filter 161. The adaptive filter 161 modifies the filter coefficients based on the input error signal, and generates a first pseudo echo signal by convolving the modified filter coefficients and the reproduced signal. The adaptive filter 161 uses an adaptive algorithm to modify filter coefficients so that the error signal is minimized. As the adaptive algorithm, for example, a learning identification method (NLMS (Normalized Least Mean Square) method), an affine projection method, or a recursive least squares method (RLS (Recursive Least Square) method) is used.

The second echo canceller 17 uses at least one input signal output from at least two microphones and a first pseudo echo signal generated by the first echo canceller 16 to adjust the at least one input signal. A second pseudo echo signal indicating a component of the included first pseudo echo signal is generated, and the generated second pseudo echo signal is used to cancel the acoustic echo component of the at least one input signal.

The second echo canceller 17 includes a third echo canceller 18 that cancels the acoustic echo component of the first input signal and a fourth echo canceller 19 that cancels the acoustic echo component of the second input signal. The first pseudo echo signal generated by the first echo canceller 16 is output to the third echo canceller 18 and the fourth echo canceller 19.

The third echo canceller 18 uses the first input signal and the first pseudo echo signal generated by the first echo canceller 16 to cancel the first pseudo echo signal included in the first input signal. A third pseudo-echo signal representing a component of is generated, and the acoustic echo component of the first input signal is canceled using the generated third pseudo-echo signal.

The third echo canceller 18 includes an adaptive filter 181 and an error calculation section 182.

Adaptive filter 181 generates a third pseudo-echo signal indicating a component of the first pseudo-echo signal included in the first input signal by convolving the filter coefficients and the first pseudo-echo signal.

The error calculation unit 182 calculates an error signal between the first input signal from the first microphone 11 and the third pseudo echo signal from the adaptive filter 181, and outputs the calculated error signal to the adaptive filter 181. The adaptive filter 181 modifies the filter coefficients based on the input error signal, and generates a third pseudo echo signal by convolving the modified filter coefficients with the first pseudo echo signal. The adaptive filter 181 uses an adaptive algorithm to modify filter coefficients so that the error signal is minimized. As the adaptive algorithm, for example, a learning identification method, an affine projection method, or a recursive least squares method is used.

Furthermore, the error calculation unit 182 cancels the acoustic echo component from the first input signal by subtracting the third pseudo echo signal from the adaptive filter 181 from the first input signal from the first microphone 11. do. Therefore, the error calculation unit 182 outputs the first input signal with the acoustic echo component canceled to the first output terminal 20.

The fourth echo canceller 19 uses the second input signal and the first pseudo echo signal generated by the first echo canceller 16 to cancel the first pseudo echo signal included in the second input signal. A fourth pseudo echo signal representing a component of is generated, and the acoustic echo component of the second input signal is canceled using the generated fourth pseudo echo signal.

The fourth echo canceller 19 includes an adaptive filter 191 and an error calculation section 192.

The adaptive filter 191 generates a fourth pseudo-echo signal representing a component of the first pseudo-echo signal included in the second input signal by convolving the filter coefficients and the first pseudo-echo signal.

The error calculation unit 192 calculates an error signal between the second input signal from the second microphone 12 and the fourth pseudo echo signal from the adaptive filter 191, and outputs the calculated error signal to the adaptive filter 191. The adaptive filter 191 modifies the filter coefficients based on the input error signal, and generates a fourth pseudo echo signal by convolving the modified filter coefficients with the first pseudo echo signal. Adaptive filter 191 uses an adaptive algorithm to modify filter coefficients so that the error signal is minimized. As the adaptive algorithm, for example, a learning identification method, an affine projection method, or a recursive least squares method is used.

Furthermore, the error calculation unit 192 cancels the acoustic echo component from the second input signal by subtracting the fourth pseudo echo signal from the adaptive filter 191 from the second input signal from the second microphone 12. do. Therefore, the error calculation unit 192 outputs the second input signal with the acoustic echo component canceled to the second output terminal 21.

Note that in the first embodiment, the filter length of the second echo canceller 17 is shorter than the filter length of the first echo canceller 16. That is, the filter length of the adaptive filter 181 of the third echo canceller 18 is shorter than the filter length of the adaptive filter 161 of the first echo canceller 16, and the filter length of the adaptive filter 191 of the fourth echo canceller 19 is shorter than the filter length of the adaptive filter 161 of the first echo canceller 16. It is shorter than the filter length of the adaptive filter 161 of the echo canceller 16.

Note that in the first embodiment, the communication device includes two microphones, but the present disclosure is not particularly limited thereto, and may include three or more microphones. When the communication device includes three or more microphones, the adder 13 adds each input signal from the three or more microphones, and the first echo canceller 16 is provided for each of the three or more microphones. A first pseudo-echo signal is output to the echo canceller.

Further, in the first embodiment, the communication device includes one speaker, but the present disclosure is not particularly limited thereto, and may include two or more speakers. When the communication device includes a plurality of speakers, the communication device needs to include the same number of acoustic echo canceling devices 1 as the plurality of speakers.

Next, the operation of the acoustic echo canceling device 1 in Embodiment 1 of the present disclosure will be described.

FIG. 2 is a flowchart for explaining the operation of the acoustic echo canceling device in Embodiment 1 of the present disclosure.

First, in step S1, the adder 13 adds the first input signal from the first microphone 11 and the second input signal from the second microphone 12. At this time, the first input signal from the first microphone 11 and the second input signal from the second microphone 12 are input to the adder 13 .

Next, in step S2, the adaptive filter 161 of the first echo canceller 16 generates a first pseudo echo signal indicating the component of the reproduced signal included in the added signal by convolving the filter coefficient and the reproduced signal. .

Next, in step S3, the error calculation section 162 subtracts the first pseudo echo signal from the adaptive filter 161 from the addition signal from the addition section 13, thereby making the difference between the addition signal and the first pseudo echo signal. Calculate the error signal. Error calculating section 162 outputs the calculated error signal to adaptive filter 161.

Next, in step S4, the adaptive filter 161 modifies the filter coefficients based on the error signal input from the error calculation unit 162. The adaptive filter 161 generates a first pseudo echo signal by convolving the modified filter coefficients and the reproduced signal.

Next, in step S5, the adaptive filter 161 outputs the generated first pseudo echo signal to the third echo canceller 18 and the fourth echo canceller 19.

Next, in step S6, the adaptive filter 181 of the third echo canceller 18 convolves the filter coefficients with the first pseudo echo signal to obtain a component of the first pseudo echo signal included in the first input signal. A third pseudo-echo signal indicating .

Next, in step S<b>7 , the error calculation unit 182 subtracts the third pseudo echo signal from the adaptive filter 181 from the first input signal from the first microphone 11 . An error signal with respect to the third pseudo echo signal is calculated. The error calculation unit 182 outputs the calculated error signal to the adaptive filter 181.

Next, in step S8, the adaptive filter 181 modifies the filter coefficients based on the error signal input from the error calculation unit 182. The adaptive filter 181 generates a third pseudo echo signal by convolving the modified filter coefficients and the first pseudo echo signal.

Next, in step S9, the error calculation unit 182 outputs the first input signal with the acoustic echo component canceled to the first output terminal 20. That is, the error calculation unit 182 cancels the acoustic echo component from the first input signal by subtracting the third pseudo echo signal from the adaptive filter 181 from the first input signal from the first microphone 11. do.

Next, in step S10, the adaptive filter 191 of the fourth echo canceller 19 convolves the filter coefficients with the first pseudo echo signal to obtain the component of the first pseudo echo signal included in the second input signal. A fourth pseudo-echo signal is generated.

Next, in step S11, the error calculation unit 192 subtracts the fourth pseudo echo signal from the adaptive filter 191 from the second input signal from the second microphone 12, thereby converting the second input signal to the second input signal. An error signal with respect to the fourth pseudo echo signal is calculated. Error calculating section 192 outputs the calculated error signal to adaptive filter 191.

Next, in step S12, the adaptive filter 191 modifies the filter coefficients based on the error signal input from the error calculation unit 192. The adaptive filter 191 generates a fourth pseudo echo signal by convolving the modified filter coefficients and the first pseudo echo signal.

Next, in step S13, the error calculation unit 192 outputs the second input signal with the acoustic echo component canceled to the second output terminal 21. That is, the error calculation unit 192 cancels the acoustic echo component from the second input signal by subtracting the fourth pseudo echo signal from the adaptive filter 191 from the second input signal from the second microphone 12. do.

Note that at the initial stage when the acoustic echo canceling device 1 starts operating, the filter coefficients are not sufficiently modified, so that the acoustic echo component cannot be sufficiently canceled from the first input signal and the second input signal. However, by repeatedly performing the processing of steps S1 to S13, the filter coefficients are sufficiently modified so that the acoustic echo components can be sufficiently canceled from the first input signal and the second input signal. Become.

In this way, the first echo canceller 16 generates a first pseudo echo signal indicating the components of the reproduced signal contained in the input signals obtained from at least two microphones, and the second echo canceller 17 generates at least one A second pseudo echo signal representing a component of the first pseudo echo signal included in the two input signals is generated, and the acoustic echo component of the at least one input signal is canceled using the generated second pseudo echo signal. Ru.

Therefore, since the second pseudo echo signal is generated using the already generated first pseudo echo signal, the filter length (tap length) of the adaptive filter used when generating the second pseudo echo signal This makes it possible to maintain communication performance and reduce the amount of calculation required to remove acoustic echoes.

In particular, the echo canceling process by the first stage echo canceller (first echo canceller 16) has the same filter length (amount of calculation) as the conventional one; Since the echo canceller 18 and the fourth echo canceller 19) use the already generated first pseudo echo signal, the filter length can be made shorter than before, and as a result, the echo cancellation processing by the echo canceller 18 and the fourth echo canceller 19) The amount of calculation can be reduced. Therefore, as the number of microphones increases, the amount of calculation can be further reduced compared to the conventional method.

In the first embodiment, the first echo canceller 16 outputs an added signal obtained by adding the first input signal from the first microphone 11 and the second input signal from the second microphone 12, and the speaker 15. The first pseudo echo signal is generated using the reproduced signal. This can be said to estimate the acoustic echo input from the speaker 15 to a virtual microphone placed at an intermediate position between the first microphone 11 and the second microphone 12. The third echo canceller 18 uses the first pseudo echo signal generated by the first echo canceller 16 to generate a third pseudo echo signal. This can be said to estimate an acoustic echo corresponding to the difference between the virtual microphone position and the first microphone 11 position. Therefore, the filter length of the adaptive filter 181 of the third echo canceller 18 can be made significantly shorter than the filter length of the adaptive filter 161 of the first echo canceller 16. Similarly, the filter length of the adaptive filter 191 of the fourth echo canceller 19 can be significantly shorter than the filter length of the adaptive filter 161 of the first echo canceller 16.

For example, the amount of calculation for the third echo canceller 18 and the fourth echo canceller 19 can be reduced to about one tenth of the amount of calculation for the first echo canceller 16. Therefore, the total calculation amount of the first echo canceller 16, the third echo canceller 18, and the fourth echo canceller 19 is the same as that of the first echo canceler 16 for each of the first microphone 11 and the second microphone 12. The amount of calculation can be made sufficiently smaller than the total amount of calculation when two echo cancellers are provided.

Furthermore, the plurality of microphones are arranged at different positions. Therefore, the waveform of the reflected wave (echo signal) input as an acoustic echo differs for each of the plurality of microphones. If the phase of the echo signal is opposite to the input signal, which is the speaker's voice, the echo signal is added to the input signal, causing the input signal to disappear and canceling the acoustic echo of the input signal. becomes difficult. However, in the first embodiment, since the first input signal and the second input signal from at least two microphones are added, it is possible to reduce the influence of signal loss due to interference of acoustic echoes.

In the first embodiment, the first echo canceller 16 receives the time domain reproduction signal and the time domain addition signal, and the second echo canceller 17 receives the time domain first input signal. , the second input signal in the time domain and the first pseudo echo signal in the time domain are input, but the present disclosure is not particularly limited thereto. Even if the addition signal in the frequency domain is input, and the first input signal in the frequency domain, the second input signal in the frequency domain, and the first pseudo echo signal in the frequency domain are input to the second echo canceller 17, good. Hereinafter, a first modification of the first embodiment will be described.

FIG. 3 is a diagram illustrating a configuration of a telephone communication device in a first modification of the first embodiment of the present disclosure.

The telephone device shown in FIG. 3 includes an acoustic echo canceling device 1A, a first microphone 11, a second microphone 12, an input terminal 14, a speaker 15, a first output terminal 20, and a second output terminal 21. In the first modification of the first embodiment, the same components as those in the first embodiment are given the same reference numerals, and the description thereof will be omitted.

The acoustic echo canceling device 1A includes an adding section 13, a first echo canceller 16, a second echo canceller 17, fast Fourier transform sections 24, 25, 28, 29, and inverse fast Fourier transform sections 30, 31.

The fast Fourier transform units 24, 25, 28, and 29 perform discrete Fourier transform at high speed. The fast Fourier transform unit 24 converts the time-domain reproduction signal input to the first echo canceller 16 into a frequency-domain reproduction signal. The fast Fourier transform unit 25 converts the time domain addition signal (input signal) input from the addition unit 13 to the first echo canceller 16 into a frequency domain addition signal (input signal).

The fast Fourier transform unit 28 transforms a first input signal (at least one input signal) in the time domain input from the first microphone 11 to the third echo canceller 18 into a first input signal (at least one input signal) in the frequency domain. input signal). The fast Fourier transform unit 29 transforms a second input signal (at least one input signal) in the time domain input from the second microphone 12 to the fourth echo canceller 19 into a second input signal (at least one input signal) in the frequency domain. input signal).

The inverse fast Fourier transform units 30 and 31 perform inverse discrete Fourier transform at high speed. The inverse fast Fourier transform unit 30 converts the first input signal in the frequency domain input from the third echo canceller 18 to the first output terminal 20 into the first input signal in the time domain. The inverse fast Fourier transform unit 31 converts the second input signal in the frequency domain input from the fourth echo canceller 19 to the second output terminal 21 into a second input signal in the time domain.

The first echo canceller 16 generates a first pseudo echo signal in the frequency domain using the frequency domain addition signal and the frequency domain reproduction signal.

The third echo canceller 18 generates a third pseudo echo signal in the frequency domain using the first input signal in the frequency domain and the first pseudo echo signal in the frequency domain, and The third pseudo-echo signal is used to cancel the acoustic echo component of the first input signal in the frequency domain.

The fourth echo canceller 19 generates a fourth pseudo echo signal in the frequency domain using the second input signal in the frequency domain and the first pseudo echo signal in the frequency domain, and The fourth pseudo-echo signal is used to cancel the acoustic echo component of the second input signal in the frequency domain.

In the first modification of the first embodiment, the adaptive filters 161, 181, and 191 can use a frequency domain adaptive algorithm, and the convolution operation can be performed by multiplication, so that the amount of calculation can be further reduced. can.

Note that in the first embodiment, depending on the arrangement position of the first microphone 11, the first input signal from the first microphone 11 and the first pseudo echo signal generated by the first echo canceller 16 may be There may be a time difference between the two. For example, when the sound from the speaker 15 is input to the first microphone 11, the first input signal from the first microphone 11 includes a first pseudo echo signal generated by the first echo canceller 16. There is a possibility that an echo signal that is faster in time than that is included. In this case, theoretically, the third echo canceller 18 may not be able to estimate the echo signal included in the first input signal using the first pseudo echo signal. Therefore, the acoustic echo canceling device may further include a delay unit that delays at least one input signal output from the at least two microphones. A second modification of the first embodiment will be described below.

FIG. 10 is a diagram illustrating a configuration of a telephone communication device in a second modification of the first embodiment of the present disclosure.

The telephone device shown in FIG. 10 includes an acoustic echo canceling device 1F, a first microphone 11, a second microphone 12, an input terminal 14, a speaker 15, a first output terminal 20, and a second output terminal 21. In addition, in the second modification of the first embodiment, the same components as in the first embodiment are given the same reference numerals, and the description thereof will be omitted.

The acoustic echo canceling device 1F includes an adding section 13, a first echo canceller 16, a second echo canceller 17, and a delay section 80.

The delay unit 80 delays at least one input signal output from at least two microphones. The delay section 80 includes a first delay section 81 and a second delay section 82.

The first delay section 81 is arranged between the first microphone 11 and the third echo canceller 18. The first delay section 81 delays the first input signal from the first microphone 11.

The second delay section 82 is arranged between the second microphone 12 and the fourth echo canceller 19. The second delay section 82 delays the second input signal from the second microphone 12.

The second echo canceller 17 uses the delayed at least one input signal and the first pseudo-echo signal generated by the first echo canceller 16 to be included in the delayed at least one input signal. A second pseudo echo signal representing a component of the first pseudo echo signal is generated, and the generated second pseudo echo signal is used to cancel the acoustic echo component of the delayed at least one input signal.

The third echo canceller 18 uses the delayed first input signal and the first pseudo-echo signal generated by the first echo canceller 16 to generate a signal included in the delayed first input signal. A third pseudo echo signal representing a component of the first pseudo echo signal is generated, and the generated third pseudo echo signal is used to cancel the acoustic echo component of the delayed first input signal.

The fourth echo canceller 19 uses the delayed second input signal and the first pseudo-echo signal generated by the first echo canceller 16 to include the delayed second input signal. A fourth pseudo echo signal representing a component of the first pseudo echo signal is generated, and the generated fourth pseudo echo signal is used to cancel the delayed acoustic echo component of the second input signal.

In the second modification of the first embodiment, the first input signal delayed by the first delay section 81 is input to the third echo canceller 18, and the second input signal delayed by the second delay section 82 is input to the third echo canceller 18. Since the input signal is input to the fourth echo canceller 19, the time difference between the first pseudo echo signal generated by the first echo canceller 16 and the first input signal is eliminated, and the first pseudo echo signal The time difference between the input signal and the second input signal is eliminated, and the third pseudo echo signal and the fourth pseudo echo signal can be reliably generated.

In addition, in the first modification of the first embodiment, the acoustic echo canceling device 1A may include a first delay section 81 between the first microphone 11 and the fast Fourier transform section 28, and A second delay section 82 may be provided between the microphone 12 and the fast Fourier transform section 29.

Further, in the first embodiment, the adder 13 adds the first input signal from the first microphone 11 and the second input signal from the second microphone 12, and the first echo canceller 16 adds the first input signal from the first microphone 11 and the second input signal from the second microphone 12. Although the first pseudo echo signal indicating the component of the reproduced signal included in the added signal is generated using the added signal and the reproduced signal, the present disclosure is not particularly limited to this, and the acoustic echo canceling device 1 may further include an averaging processing section that averages the added signal from the adding section 13. In this case, the first echo canceller 16 may generate a first pseudo echo signal indicating a component of the reproduced signal included in the averaged signal using the averaged signal from the averaging processing section and the reproduced signal. good.

(Embodiment 2)
In the first embodiment, the first pseudo echo signal generated by the first echo canceller is output to the third echo canceller and the fourth echo canceller, and the third echo canceler outputs the first pseudo echo signal. The fourth echo canceller uses the first pseudo echo signal to cancel the acoustic echo component of the second input signal. In this case, the first echo canceler generates a first pseudo echo signal and cancels the acoustic echo component of the first input signal using the first pseudo echo signal, and the second echo canceller generates the acoustic echo component of the first input signal. The first pseudo echo signal is used to cancel the acoustic echo component of the second input signal.

FIG. 4 is a diagram illustrating the configuration of a communication device according to Embodiment 2 of the present disclosure.

The communication device shown in FIG. 4 includes an acoustic echo canceling device 1B, a first microphone 11, a second microphone 12, an input terminal 14, a speaker 15, a first output terminal 20, and a second output terminal 21. Note that in the second embodiment, the same components as in the first embodiment are given the same reference numerals, and the description thereof will be omitted.

The acoustic echo canceling device 1B includes a first echo canceller 41 and a second echo canceller 42.

The first echo canceller 41 generates a first pseudo echo signal indicating a component of the reproduced signal included in the input signal, using input signals obtained from at least two microphones and a reproduced signal output to the speaker. do.

It is preferable that the first echo canceller 41 generates the first pseudo echo signal for the microphone located closest to the speaker 15. In this case, the first echo canceller 41 uses the input signal and the reproduced signal output from the microphone located closest to the speaker 15 to generate a first pseudo echo signal indicating the component of the reproduced signal included in the input signal. generate. In the second embodiment, the microphone located closest to the speaker 15 is the first microphone 11.

In the second embodiment, the input signals obtained from at least two microphones are the first input signal from the first microphone 11. That is, the first echo canceller 41 uses the first input signal and the reproduced signal to generate a first pseudo echo signal indicating the component of the reproduced signal included in the first input signal. Further, the first echo canceller 41 cancels the acoustic echo component of the first input signal using the generated first pseudo echo signal.

The first echo canceller 41 includes an adaptive filter 411 and an error calculation section 412.

The adaptive filter 411 generates a first pseudo echo signal indicating a component of the reproduced signal included in the first input signal by convolving the filter coefficient and the reproduced signal.

The error calculation unit 412 calculates an error signal between the first input signal from the first microphone 11 and the first pseudo echo signal from the adaptive filter 411, and outputs the calculated error signal to the adaptive filter 411. The adaptive filter 411 modifies the filter coefficients based on the input error signal, and generates a first pseudo echo signal by convolving the modified filter coefficients with the reproduced signal. Adaptive filter 411 uses an adaptive algorithm to modify filter coefficients so that the error signal is minimized. As the adaptive algorithm, for example, a learning identification method, an affine projection method, or a recursive least squares method is used.

Furthermore, the error calculation unit 412 cancels the acoustic echo component from the first input signal by subtracting the first pseudo echo signal from the adaptive filter 411 from the first input signal from the first microphone 11. do. Therefore, the error calculation unit 412 outputs the first input signal with the acoustic echo component canceled to the first output terminal 20.

The first pseudo echo signal generated by the first echo canceller 41 is output to the second echo canceller 42.

The second echo canceller 42 uses the second input signal and the first pseudo echo signal generated by the first echo canceller 41 to cancel the first pseudo echo signal included in the second input signal. A second pseudo-echo signal representing a component of is generated, and the acoustic echo component of the second input signal is canceled using the generated second pseudo-echo signal.

The second echo canceller 42 includes an adaptive filter 421 and an error calculation section 422.

The adaptive filter 421 generates a second pseudo echo signal indicating a component of the first pseudo echo signal included in the second input signal by convolving the filter coefficients and the first pseudo echo signal.

The error calculation unit 422 calculates an error signal between the second input signal from the second microphone 12 and the second pseudo echo signal from the adaptive filter 421, and outputs the calculated error signal to the adaptive filter 421. The adaptive filter 421 modifies filter coefficients based on the input error signal, and generates a second pseudo echo signal by convolving the modified filter coefficients with the first pseudo echo signal. The adaptive filter 421 uses an adaptive algorithm to modify filter coefficients so that the error signal is minimized. As the adaptive algorithm, for example, a learning identification method, an affine projection method, or a recursive least squares method is used.

Furthermore, the error calculation unit 422 cancels the acoustic echo component from the second input signal by subtracting the second pseudo echo signal from the adaptive filter 421 from the second input signal from the second microphone 12. do. Therefore, the error calculation unit 422 outputs the second input signal with the acoustic echo component canceled to the second output terminal 21.

Note that in the second embodiment, the communication device includes two microphones, but the present disclosure is not particularly limited thereto, and may include three or more microphones. When the telephone device includes three or more microphones, the first echo canceller 41 outputs the first pseudo echo signal to the echo cancellers provided for each of the microphones other than the first microphone 11. .

Further, in the second embodiment, the communication device includes one speaker, but the present disclosure is not particularly limited thereto, and may include two or more speakers. When the communication device includes a plurality of speakers, the communication device needs to include the same number of acoustic echo canceling devices 1B as the plurality of speakers.

Next, the operation of the acoustic echo canceling device 1B in Embodiment 2 of the present disclosure will be described.

FIG. 5 is a flowchart for explaining the operation of the acoustic echo canceling device in Embodiment 2 of the present disclosure.

First, in step S21, the adaptive filter 411 of the first echo canceller 41 convolves the filter coefficient and the reproduced signal to generate a first pseudo echo signal indicating the component of the reproduced signal included in the first input signal. generate.

Next, in step S<b>22 , the error calculation unit 412 subtracts the first pseudo echo signal from the adaptive filter 411 from the first input signal from the first microphone 11 . An error signal with respect to the first pseudo echo signal is calculated. The error calculation unit 412 outputs the calculated error signal to the adaptive filter 411.

Next, in step S23, the adaptive filter 411 modifies the filter coefficients based on the error signal input from the error calculation unit 412. The adaptive filter 411 generates a first pseudo echo signal by convolving the modified filter coefficients and the reproduced signal.

Next, in step S24, the error calculation unit 412 outputs the first input signal with the acoustic echo component canceled to the first output terminal 20. That is, the error calculation unit 412 cancels the acoustic echo component from the first input signal by subtracting the first pseudo echo signal from the adaptive filter 411 from the first input signal from the first microphone 11. do.

Next, in step S25, the adaptive filter 411 outputs the generated first pseudo echo signal to the second echo canceller 42.

Next, in step S26, the adaptive filter 421 of the second echo canceller 42 convolves the filter coefficients with the first pseudo echo signal to obtain the component of the first pseudo echo signal included in the second input signal. A second pseudo-echo signal indicating .

Next, in step S27, the error calculation unit 422 subtracts the second pseudo echo signal from the adaptive filter 421 from the second input signal from the second microphone 12, thereby converting the second input signal to the second input signal from the second microphone 12. An error signal with respect to the second pseudo echo signal is calculated. The error calculation unit 422 outputs the calculated error signal to the adaptive filter 421.

Next, in step S28, the adaptive filter 421 modifies the filter coefficients based on the error signal input from the error calculation unit 422. The adaptive filter 421 generates a second pseudo echo signal by convolving the modified filter coefficients and the first pseudo echo signal.

Next, in step S29, the error calculation unit 422 outputs the second input signal with the acoustic echo component canceled to the second output terminal 21. That is, the error calculation unit 422 cancels the acoustic echo component from the second input signal by subtracting the second pseudo echo signal from the adaptive filter 421 from the second input signal from the second microphone 12. do.

Note that at the initial stage when the acoustic echo canceling device 1B starts operating, the filter coefficients are not sufficiently modified, so that the acoustic echo component cannot be sufficiently canceled from the first input signal and the second input signal. However, by repeatedly performing the processing from step S21 to step S29, the filter coefficients are sufficiently modified so that the acoustic echo component can be sufficiently canceled from the first input signal and the second input signal. Become.

In this way, the first echo canceller 41 generates the first pseudo echo signal indicating the component of the reproduced signal contained in the first input signal obtained from the first microphone 11, and The acoustic echo component of the first input signal is canceled using the pseudo echo signal, and the second echo canceler 42 generates a second pseudo echo indicating the component of the first pseudo echo signal included in the second input signal. A signal is generated, and the generated second pseudo-echo signal is used to cancel the acoustic echo component of the second input signal.

Therefore, since the second pseudo echo signal is generated using the already generated first pseudo echo signal, the filter length (tap length) of the adaptive filter used when generating the second pseudo echo signal This makes it possible to maintain communication performance and reduce the amount of calculation required to remove acoustic echoes.

In particular, the echo canceling process by the first-stage echo canceller (first echo canceller 41) has the same filter length (amount of calculation) as the conventional one; Since the echo canceller 42) uses the already generated first pseudo echo signal, the filter length can be made shorter than before, and as a result, the amount of calculation can be reduced more than before. can. Therefore, as the number of microphones increases, the amount of calculation can be further reduced compared to the conventional method.

In the second embodiment, the first echo canceller 41 generates a first pseudo echo signal using the first input signal from the first microphone 11 and the reproduction signal to the speaker 15. There is. This can be said to estimate the acoustic echo input from the speaker 15 to the first microphone 11. Then, the second echo canceller 42 uses the first pseudo echo signal generated by the first echo canceller 16 to generate a second pseudo echo signal. This can be said to estimate an acoustic echo corresponding to the difference between the position of the first microphone 11 and the position of the second microphone 12. Therefore, the filter length of the adaptive filter 421 of the second echo canceller 42 can be made significantly shorter than the filter length of the adaptive filter 411 of the first echo canceller 41.

For example, the amount of calculation for the second echo canceller 42 can be reduced to about one tenth of the amount of calculation for the first echo canceller 41. Therefore, the total calculation amount of the first echo canceller 41 and the second echo canceller 42 is two echo cancellers with the same calculation amount as the first echo canceller 41 for each of the first microphone 11 and the second microphone 12. The total amount of calculations can be sufficiently reduced compared to the case where .

Note that in the second embodiment, the acoustic echo canceling device 1B may include a delay section between the second microphone 12 and the second echo canceller 42.

In the second embodiment, the first echo canceller 41 receives the time domain reproduction signal and the time domain first input signal, and the second echo canceller 42 receives the time domain second input signal. The input signal and the first pseudo echo signal in the time domain are input to the first echo canceller 41, however, the present disclosure is not particularly limited thereto. An input signal is input, and the second echo canceller 42 may be input with a second input signal in the frequency domain and a first pseudo echo signal in the frequency domain. A modification of this second embodiment will be described below.

FIG. 6 is a diagram showing the configuration of a telephone communication device in a modification of the second embodiment of the present disclosure.

The communication device shown in FIG. 6 includes an acoustic echo canceling device 1C, a first microphone 11, a second microphone 12, an input terminal 14, a speaker 15, a first output terminal 20, and a second output terminal 21. In addition, in the modification of Embodiment 2, the same code|symbol is attached|subjected to the same structure as Embodiment 2, and description is abbreviate|omitted.

The acoustic echo canceling device 1C includes a first echo canceller 41, a second echo canceller 42, fast Fourier transform sections 45, 46, and 49, and inverse fast Fourier transform sections 50 and 51.

Fast Fourier transform units 45, 46, and 49 perform discrete Fourier transform at high speed. The fast Fourier transform unit 45 converts the time-domain reproduction signal input to the first echo canceller 41 into a frequency-domain reproduction signal. The fast Fourier transform unit 46 converts a first input signal in the time domain input from the first microphone 11 to the first echo canceller 41 into a first input signal in the frequency domain. The fast Fourier transform unit 49 converts a second input signal in the time domain input from the second microphone 12 to the second echo canceller 42 into a second input signal in the frequency domain.

The inverse fast Fourier transform units 50 and 51 perform inverse discrete Fourier transform at high speed. The inverse fast Fourier transform unit 50 converts a first input signal in the frequency domain input from the first echo canceller 41 to the first output terminal 20 into a first input signal in the time domain. The inverse fast Fourier transform unit 51 converts a second input signal in the frequency domain, which is input from the second echo canceller 42 to the second output terminal 21, into a second input signal in the time domain.

The first echo canceller 41 generates a first pseudo echo signal in the frequency domain using the first input signal in the frequency domain and the reproduced signal in the frequency domain, and generates a first pseudo echo in the frequency domain. The signal is used to cancel acoustic echo components of the first input signal in the frequency domain.

The second echo canceller 42 generates a second pseudo echo signal in the frequency domain using the second input signal in the frequency domain and the first pseudo echo signal in the frequency domain, and The second pseudo-echo signal is used to cancel the acoustic echo component of the second input signal in the frequency domain.

In the modified example of the second embodiment, the adaptive filters 411 and 421 can use a frequency domain adaptive algorithm, and the convolution operation can be performed by multiplication, so that the amount of calculation can be further reduced.

Note that in a modification of the second embodiment, the acoustic echo canceling device 1C may include a delay section between the second microphone 12 and the fast Fourier transform section 49.

(Embodiment 3)
In the first embodiment, the first echo canceller uses the addition signal from the addition section and the reproduction signal to generate the first pseudo echo signal indicating the component of the reproduction signal included in the addition signal. In the third embodiment, the first echo canceller calculates a first error signal indicating an error between the first input signal and the first pseudo echo signal, and calculates the first error signal indicating the error between the second input signal and the first pseudo echo signal. A second error signal indicating the error with the echo signal is calculated, the summed signal obtained by adding the first error signal and the second error signal is averaged, and the average signal is calculated using the average signal and the reproduced signal. A first pseudo echo signal indicating the included components of the reproduced signal is generated.

FIG. 7 is a diagram illustrating the configuration of a telephone communication device according to Embodiment 3 of the present disclosure.

The communication device shown in FIG. 7 includes an acoustic echo canceling device 1D, a first microphone 11, a second microphone 12, an input terminal 14, a speaker 15, a first output terminal 20, and a second output terminal 21. In addition, in Embodiment 3, the same components as in Embodiment 1 are given the same reference numerals, and description thereof will be omitted.

The acoustic echo canceling device 1D includes a first echo canceller 61 and a second echo canceller 17.

The first echo canceller 61 generates a first pseudo echo signal indicating a component of the reproduced signal included in the input signal, using input signals obtained from at least two microphones and a reproduced signal output to the speaker. do.

In the third embodiment, the input signals obtained from at least two microphones include a first error signal indicating an error between the first input signal and the first pseudo echo signal, and a first error signal indicating the error between the second input signal and the first pseudo echo signal. This is an average signal obtained by averaging the summed signal obtained by adding the second error signal indicating the error with the pseudo echo signal. That is, the first echo canceller 61 uses the average signal and the reproduced signal to generate a first pseudo echo signal indicating the component of the reproduced signal included in the average signal.

The first echo canceller 61 includes an adaptive filter 611, a first error calculation section 612, a second error calculation section 613, and an average processing section 614.

The adaptive filter 611 generates a first pseudo echo signal indicating the component of the reproduced signal included in the average signal by convolving the filter coefficient and the reproduced signal.

The first error calculation unit 612 calculates a first error signal indicating the error between the first input signal and the first pseudo echo signal. The first error calculation unit 612 outputs the calculated first error signal to the second error calculation unit 613.

The second error calculation unit 613 calculates a second error signal indicating the error between the second input signal and the first pseudo echo signal, and adds the first error signal and the second error signal. do. The second error calculation unit 613 outputs a sum signal obtained by adding the first error signal and the second error signal to the average processing unit 614.

The averaging processing unit 614 averages the sum signal obtained by adding the first error signal and the second error signal. The average processing unit 614 outputs to the adaptive filter 611 an average signal obtained by averaging the summed signal obtained by adding the first error signal and the second error signal.

The adaptive filter 611 uses the average signal from the average processing section 614 and the reproduced signal to generate a first pseudo echo signal indicating a component of the reproduced signal included in the average signal. The adaptive filter 611 modifies the filter coefficients based on the input average signal, and generates a first pseudo echo signal by convolving the modified filter coefficients and the reproduced signal. Adaptive filter 611 uses an adaptive algorithm to modify filter coefficients so that the average signal is minimized. As the adaptive algorithm, for example, a learning identification method, an affine projection method, or a recursive least squares method is used.

The first pseudo echo signal generated by the first echo canceller 61 is output to the third echo canceller 18 and the fourth echo canceller 19.

Note that in the third embodiment, the communication device includes two microphones, but the present disclosure is not particularly limited thereto, and may include three or more microphones. When the communication device includes three or more microphones, the first echo canceller 61 adds and averages each error signal between each input signal from the three or more microphones and the first pseudo echo signal, and A first pseudo echo signal is output to an echo canceller provided for each of the above microphones.

Further, in the third embodiment, the communication device includes one speaker, but the present disclosure is not particularly limited thereto, and may include two or more speakers. When the communication device includes a plurality of speakers, the communication device needs to include the same number of acoustic echo canceling devices 1D as the plurality of speakers.

Next, the operation of the acoustic echo canceling device 1D in Embodiment 3 of the present disclosure will be described.

FIG. 8 is a flowchart for explaining the operation of the acoustic echo canceling device in Embodiment 3 of the present disclosure.

First, in step S41, the adaptive filter 611 of the first echo canceller 61 generates a first pseudo echo signal indicating the component of the reproduced signal included in the average signal by convolving the filter coefficient and the reproduced signal.

Next, in step S42, the first error calculation unit 612 subtracts the first pseudo echo signal from the adaptive filter 611 from the first input signal from the first microphone 11. A first error signal, which is the difference between the input signal and the first pseudo echo signal, is calculated. The first error calculation unit 612 outputs the calculated first error signal to the second error calculation unit 613.

Next, in step S43, the second error calculation unit 613 subtracts the first pseudo echo signal from the adaptive filter 611 from the second input signal from the second microphone 12, thereby obtaining the second input signal from the second microphone 12. A second error signal, which is the difference between the input signal and the first pseudo echo signal, is calculated.

Next, in step S44, the second error calculation unit 613 adds the first error signal and the second error signal. The second error calculation unit 613 outputs a sum signal of the calculated first error signal and second error signal to the average processing unit 614.

Next, in step S45, the averaging processing unit 614 averages the sum signal of the first error signal and the second error signal. The average processing unit 614 outputs an average signal obtained by averaging the added signals to the adaptive filter 611.

Next, in step S46, the adaptive filter 611 modifies the filter coefficients based on the average signal input from the average processing unit 614. The adaptive filter 611 generates a first pseudo echo signal by convolving the modified filter coefficients and the reproduced signal.

Next, in step S47, the adaptive filter 611 outputs the generated first pseudo echo signal to the third echo canceller 18 and the fourth echo canceller 19.

Next, in step S48, the adaptive filter 181 of the third echo canceller 18 convolves the filter coefficients with the first pseudo echo signal to obtain a component of the first pseudo echo signal included in the first input signal. A third pseudo-echo signal indicating .

Next, in step S49, the error calculation unit 182 subtracts the third pseudo echo signal from the adaptive filter 181 from the first input signal from the first microphone 11, thereby making the first input signal A third error signal with respect to the third pseudo echo signal is calculated. The error calculation unit 182 outputs the calculated third error signal to the adaptive filter 181.

Next, in step S50, the adaptive filter 181 modifies the filter coefficients based on the third error signal input from the error calculation unit 182. The adaptive filter 181 generates a third pseudo echo signal by convolving the modified filter coefficients and the first pseudo echo signal.

Next, in step S51, the error calculation unit 182 outputs the first input signal with the acoustic echo component canceled to the first output terminal 20. That is, the error calculation unit 182 cancels the acoustic echo component from the first input signal by subtracting the third pseudo echo signal from the adaptive filter 181 from the first input signal from the first microphone 11. do.

Next, in step S52, the adaptive filter 191 of the fourth echo canceller 19 convolves the filter coefficients with the first pseudo echo signal to obtain the component of the first pseudo echo signal included in the second input signal. A fourth pseudo-echo signal is generated.

Next, in step S53, the error calculation unit 192 subtracts the fourth pseudo echo signal from the adaptive filter 191 from the second input signal from the second microphone 12, thereby converting the second input signal to the second input signal. A fourth error signal with respect to the fourth pseudo echo signal is calculated. The error calculation unit 192 outputs the calculated fourth error signal to the adaptive filter 191.

Next, in step S54, the adaptive filter 191 modifies the filter coefficients based on the fourth error signal input from the error calculation unit 192. The adaptive filter 191 generates a fourth pseudo echo signal by convolving the modified filter coefficients and the first pseudo echo signal.

Next, in step S55, the error calculation unit 192 outputs the second input signal with the acoustic echo component canceled to the second output terminal 21. That is, the error calculation unit 192 cancels the acoustic echo component from the second input signal by subtracting the fourth pseudo echo signal from the adaptive filter 191 from the second input signal from the second microphone 12. do.

Note that at the initial stage when the acoustic echo canceling device 1D starts operating, the filter coefficients are not sufficiently modified, so that the acoustic echo component cannot be sufficiently canceled from the first input signal and the second input signal. However, by repeatedly performing the processing from step S41 to step S55, the filter coefficients are sufficiently modified so that the acoustic echo component can be sufficiently canceled from the first input signal and the second input signal. Become.

In this way, the first echo canceller 61 generates a first pseudo echo signal indicating the components of the reproduced signal contained in the input signals obtained from at least two microphones, and the second echo canceller 17 generates at least one pseudo echo signal. A second pseudo echo signal representing a component of the first pseudo echo signal included in the two input signals is generated, and the acoustic echo component of the at least one input signal is canceled using the generated second pseudo echo signal. Ru.

Therefore, since the second pseudo echo signal is generated using the already generated first pseudo echo signal, the filter length (tap length) of the adaptive filter used when generating the second pseudo echo signal This makes it possible to maintain communication performance and reduce the amount of calculation required to remove acoustic echoes.

In particular, the echo canceling process by the first-stage echo canceller (first echo canceller 61) has the same filter length (amount of calculation) as the conventional one; Since the echo canceller 18 and the fourth echo canceller 19) use the already generated first pseudo echo signal, the filter length can be made shorter than before, and as a result, the echo cancellation processing by the echo canceller 18 and the fourth echo canceller 19) The amount of calculation can be reduced. Therefore, as the number of microphones increases, the amount of calculation can be further reduced compared to the conventional method.

Furthermore, the plurality of microphones are arranged at different positions. Therefore, the waveform of the reflected wave (echo signal) input as an acoustic echo differs for each of the plurality of microphones. If the phase of the echo signal is opposite to the input signal, which is the speaker's voice, the echo signal is added to the input signal, causing the input signal to disappear and canceling the acoustic echo of the input signal. becomes difficult. However, in the third embodiment, since the error signals of the first input signal and the second input signal from at least two microphones are added and averaged, the effect of signal loss due to acoustic echo interference is can be reduced.

Note that in the third embodiment, the acoustic echo canceling device 1D may include a first delay section 81 between the first microphone 11 and the third echo canceller 18, and a first delay section 81 between the first microphone 11 and the third echo canceller 18. A second delay section 82 may be provided between the fourth echo canceller 19 and the second delay section 82 .

Note that in the third embodiment, the first echo canceller 61 receives a time-domain reproduction signal, a time-domain first input signal, and a time-domain second input signal; 17, a first input signal in the time domain, a second input signal in the time domain, and a first pseudo echo signal in the time domain are input, but the present disclosure is not particularly limited thereto; The echo canceller 61 receives a reproduction signal in the frequency domain, a first input signal in the frequency domain, and a second input signal in the frequency domain, and the second echo canceller 17 receives the first input signal in the frequency domain. , a frequency domain second input signal and a frequency domain first pseudo echo signal may be input. A modification of this third embodiment will be described below.

FIG. 9 is a diagram showing the configuration of a telephone communication device in a modification of the third embodiment of the present disclosure.

The communication device shown in FIG. 9 includes an acoustic echo canceling device 1E, a first microphone 11, a second microphone 12, an input terminal 14, a speaker 15, a first output terminal 20, and a second output terminal 21. In addition, in the modification of Embodiment 3, the same code|symbol is attached|subjected to the same structure as Embodiment 3, and description is abbreviate|omitted.

The acoustic echo canceling device 1E includes a first echo canceller 61, a second echo canceller 17, fast Fourier transform sections 64, 65, 66, and inverse fast Fourier transform sections 69, 70.

The fast Fourier transform units 64, 65, and 66 perform discrete Fourier transform at high speed. The fast Fourier transform unit 64 converts the time-domain reproduction signal input to the first echo canceller 61 into a frequency-domain reproduction signal. The fast Fourier transform unit 65 converts a first input signal in the time domain output from the first microphone 11 into a first input signal in the frequency domain. The fast Fourier transform unit 66 converts the second input signal in the time domain output from the second microphone 12 into a second input signal in the frequency domain.

The inverse fast Fourier transform units 69 and 70 perform inverse discrete Fourier transform at high speed. The inverse fast Fourier transform unit 69 converts the first input signal in the frequency domain input from the third echo canceller 18 to the first output terminal 20 into the first input signal in the time domain. The inverse fast Fourier transform unit 70 converts the second input signal in the frequency domain input from the fourth echo canceller 19 to the second output terminal 21 into the second input signal in the time domain.

The first echo canceller 61 generates a first pseudo echo signal in the frequency domain using the first input signal in the frequency domain, the second input signal in the frequency domain, and the reproduced signal in the frequency domain.

The third echo canceller 18 generates a third pseudo echo signal in the frequency domain using the first input signal in the frequency domain and the first pseudo echo signal in the frequency domain, and The third pseudo-echo signal is used to cancel the acoustic echo component of the first input signal in the frequency domain.

The fourth echo canceller 19 generates a fourth pseudo echo signal in the frequency domain using the second input signal in the frequency domain and the first pseudo echo signal in the frequency domain, and The fourth pseudo-echo signal is used to cancel the acoustic echo component of the second input signal in the frequency domain.

In the modified example of the third embodiment, the adaptive filters 611, 181, and 191 can use a frequency domain adaptive algorithm, and the convolution operation can be performed by multiplication, so that the amount of calculation can be further reduced. .

Note that in a modification of the third embodiment, the acoustic echo canceling device 1E may include a first delay section 81 between the first microphone 11 and the third echo canceller 18, and a second delay section 81 between the first microphone 11 and the third echo canceller 18. A second delay section 82 may be provided between the microphone 12 and the fourth echo canceller 19. In this case, the fast Fourier transform unit 65 is arranged between the branch point between the first microphone 11 and the error calculation unit 182 and the first error calculation unit 612, and the fast Fourier transform unit 65 is arranged between the branch point and the error calculation unit 182. A first delay section 81 and a fast Fourier transform section are arranged in between. Further, a fast Fourier transform unit 66 is arranged between the branch point between the second microphone 12 and the error calculation unit 192 and the second error calculation unit 613, and a fast Fourier transform unit 66 is arranged between the branch point and the error calculation unit 192. A second delay section 82 and a fast Fourier transform section are arranged at.

Note that in each of the above embodiments, each component may be configured with dedicated hardware, or may be realized by executing a software program suitable for each component. Each component may be realized by a program execution unit such as a CPU or a processor reading and executing a software program recorded on a recording medium such as a hard disk or a semiconductor memory.

Part or all of the functions of the device according to the embodiments of the present disclosure are typically realized as an LSI (Large Scale Integration), which is an integrated circuit. These may be integrated into one chip individually, or may be integrated into one chip including some or all of them. Further, circuit integration is not limited to LSI, and may be realized using a dedicated circuit or a general-purpose processor. An FPGA (Field Programmable Gate Array) that can be programmed after the LSI is manufactured, or a reconfigurable processor that can reconfigure the connections and settings of circuit cells inside the LSI may be used.

Further, some or all of the functions of the device according to the embodiment of the present disclosure may be realized by a processor such as a CPU executing a program.

Moreover, all the numbers used above are exemplified to specifically explain the present disclosure, and the present disclosure is not limited to the illustrated numbers.

Further, the order in which the steps shown in the above flowchart are executed is for illustrative purposes to specifically explain the present disclosure, and an order other than the above may be used as long as the same effect can be obtained. . Further, some of the above steps may be executed simultaneously (in parallel) with other steps.

The acoustic echo canceling device, the acoustic echo canceling method, and the acoustic echo canceling program according to the present disclosure can maintain communication performance and reduce the amount of calculation for removing acoustic echoes, so that the acoustic echo canceling device, the acoustic echo canceling method, and the acoustic echo canceling program can output from the microphone. The present invention is useful as an acoustic echo canceling device, an acoustic echo canceling method, and an acoustic echo canceling program for canceling acoustic echo components of an input signal.

1, 1A, 1B, 1C, 1D, 1E, 1F Acoustic echo cancellation device 11 First microphone 12 Second microphone 13 Adder 14 Input terminal 15 Speaker 16, 41, 61 First echo canceller 17, 42 Second echo canceller 18 third echo canceller 19 fourth echo canceller 20 first output terminal 21 second output terminal 24, 25, 28, 29, 45, 46, 49, 64, 65, 66 Fast Fourier transform section 30, 31, 50, 51, 69, 70 inverse fast Fourier transform section 80 delay section 81 first delay section 82 second delay section 161, 181, 191, 411, 421, 611 adaptive filter 162, 182, 192, 412, 422 Error calculation unit 612 First error calculation unit 613 Second error calculation unit 614 Average processing unit

Claims (11)

A first echo canceller that uses input signals obtained from at least two microphones and a reproduced signal output to a speaker to generate a first pseudo echo signal indicating a component of the reproduced signal included in the input signal. and,
Using at least one input signal output from the at least two microphones and the first pseudo echo signal generated by the first echo canceller, the first echo signal included in the at least one input signal is a second echo canceller that generates a second pseudo echo signal representing a component of the pseudo echo signal of the at least one input signal, and cancels an acoustic echo component of the at least one input signal using the generated second pseudo echo signal;
An acoustic echo cancellation device comprising: further comprising a delay unit that delays at least one input signal output from the at least two microphones,
The second echo canceller uses the delayed at least one input signal and the first pseudo-echo signal generated by the first echo canceller to generate the delayed at least one input signal. generating a second pseudo-echo signal indicating a component of the first pseudo-echo signal included in the at least one input signal, and using the generated second pseudo-echo signal to delay an acoustic echo component of the at least one input signal; cancel,
The acoustic echo canceling device according to claim 1. The at least two microphones include a first microphone that outputs a first input signal and a second microphone that outputs a second input signal,
The delay section includes a first delay section that delays the first input signal, and a second delay section that delays the second input signal,
further comprising an adder that adds the first input signal and the second input signal,
The first echo canceller uses the addition signal from the addition unit and the reproduction signal to generate the first pseudo echo signal indicating a component of the reproduction signal included in the addition signal,
The second echo canceller is
The first pseudo echo signal included in the delayed first input signal is generated using the delayed first input signal and the first pseudo echo signal generated by the first echo canceller. a third echo canceller that generates a third pseudo echo signal representing a component of an echo signal, and uses the generated third pseudo echo signal to cancel the delayed acoustic echo component of the first input signal; and,
The delayed second input signal and the first pseudo echo signal generated by the first echo canceller are used to generate the first pseudo echo signal included in the delayed second input signal. a fourth echo canceller that generates a fourth pseudo echo signal representing a component of an echo signal, and uses the generated fourth pseudo echo signal to cancel the delayed acoustic echo component of the second input signal; and,
including,
The acoustic echo canceling device according to claim 2. The at least two microphones include a first microphone that outputs a first input signal and a second microphone that outputs a second input signal,
further comprising an adder that adds the first input signal and the second input signal,
The first echo canceller uses the addition signal from the addition unit and the reproduction signal to generate the first pseudo echo signal indicating a component of the reproduction signal included in the addition signal,
The second echo canceller is
Using the first input signal and the first pseudo echo signal generated by the first echo canceller, a component of the first pseudo echo signal included in the first input signal is indicated. a third echo canceller that generates a third pseudo echo signal and cancels an acoustic echo component of the first input signal using the generated third pseudo echo signal;
Using the second input signal and the first pseudo echo signal generated by the first echo canceller, a component of the first pseudo echo signal included in the second input signal is indicated. a fourth echo canceller that generates a fourth pseudo echo signal and cancels an acoustic echo component of the second input signal using the generated fourth pseudo echo signal;
including,
The acoustic echo canceling device according to claim 1. The at least two microphones include a first microphone that outputs a first input signal and a second microphone that outputs a second input signal,
The first echo canceller uses the first input signal and the reproduced signal to generate the first pseudo echo signal indicating a component of the reproduced signal included in the first input signal, canceling the acoustic echo component of the first input signal using the generated first pseudo echo signal;
The second echo canceller uses the second input signal and the first pseudo echo signal generated by the first echo canceller to detect the first echo signal included in the second input signal. generating a second pseudo echo signal representing a component of a pseudo echo signal of the second input signal, and using the generated second pseudo echo signal to cancel the acoustic echo component of the second input signal;
The acoustic echo canceling device according to claim 1. The at least two microphones include a first microphone that outputs a first input signal and a second microphone that outputs a second input signal,
The first echo canceller includes:
a first calculation unit that calculates a first error signal indicating an error between the first input signal and the first pseudo echo signal;
a second calculation unit that calculates a second error signal indicating an error between the second input signal and the first pseudo echo signal;
an averaging processing unit that averages an added signal obtained by adding the first error signal and the second error signal;
a generation unit that uses the average signal from the average processing unit and the reproduction signal to generate the first pseudo echo signal indicating a component of the reproduction signal included in the average signal;
including;
The second echo canceller is
Using the first input signal and the first pseudo echo signal generated by the first echo canceller, a component of the first pseudo echo signal included in the first input signal is indicated. a third echo canceller that generates a third pseudo echo signal and cancels an acoustic echo component of the first input signal using the generated third pseudo echo signal;
Using the second input signal and the first pseudo echo signal generated by the first echo canceller, a component of the first pseudo echo signal included in the second input signal is indicated. a fourth echo canceller that generates a fourth pseudo echo signal and cancels an acoustic echo component of the second input signal using the generated fourth pseudo echo signal;
including,
The acoustic echo canceling device according to claim 1. a first conversion unit that converts the input signal in the time domain to an input signal in the frequency domain;
a second conversion unit that converts the reproduction signal in the time domain to a reproduction signal in the frequency domain;
a third transformation unit that transforms the at least one input signal in the time domain to at least one input signal in the frequency domain;
a fourth conversion unit that converts the first pseudo echo signal in the time domain to a first pseudo echo signal in the frequency domain;
further comprising,
The acoustic echo canceling device according to any one of claims 1 to 6. The filter length of the second echo canceller is shorter than the filter length of the first echo canceller.
The acoustic echo canceling device according to any one of claims 1 to 7. The first echo canceller generates the first pseudo echo signal to a microphone located closest to the speaker.
The acoustic echo canceling device according to any one of claims 1 to 8. An acoustic echo canceling method in an acoustic echo canceling device that cancels an acoustic echo component of an input signal output from a microphone, the method comprising:
Using input signals obtained from at least two microphones and a reproduced signal output to a speaker, a first pseudo echo signal indicating a component of the reproduced signal included in the input signal is generated,
Using at least one input signal output from the at least two microphones and the generated first pseudo echo signal, a component of the first pseudo echo signal included in the at least one input signal is generated. generate a second pseudo-echo signal indicating
canceling an acoustic echo component of the at least one input signal using the generated second pseudo echo signal;
Acoustic echo cancellation method. A first echo canceller that uses input signals obtained from at least two microphones and a reproduced signal output to a speaker to generate a first pseudo echo signal indicating a component of the reproduced signal included in the input signal. and,
Using at least one input signal output from the at least two microphones and the first pseudo echo signal generated by the first echo canceller, the first echo signal included in the at least one input signal is a computer as a second echo canceller that generates a second pseudo echo signal indicative of a component of a pseudo echo signal of the at least one input signal, and uses the generated second pseudo echo signal to cancel an acoustic echo component of the at least one input signal; Acoustic echo cancellation program that works.

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