Echo suppression device, echo suppression method, and echo suppression program

Abstract

An echo suppressing device (1G) comprises: an echo canceller (14) that suppresses a linear echo signal from an input signal acquired by a microphone (13); a spectrum envelope extraction unit (15) that extracts spectrum envelope information from a received talk signal outputted to a loudspeaker (12); a nonlinear echo estimation unit (17) that estimates spectrum envelope information of a nonlinear echo signal included in the input signal from the spectrum envelope information extracted from the received talk signal; and a nonlinear echo suppression unit (18) that suppresses a nonlinear echo from an output signal from the echo canceller (14) by using the estimated spectrum envelope information of the nonlinear echo signal.

Description

[Technical Field]

[0001] The present disclosure relates to a technique for suppressing linear and nonlinear echo signals contained in an input signal acquired by a microphone. [Background technology]

[0002] When a call is made using a speaker and a microphone in a hands-free call system, a video conference system, or the like, the voice of the speaker on the transmitting side is input to the microphone on the transmitting side and transmitted as a transmission signal to the device on the receiving side via a network line. The voice amplified from the speaker on the receiving side is picked up by the microphone on the receiving side and transmitted to the device on the transmitting side via the network line. At this time, the speaker on the transmitting side reproduces the voice that the speaker spoke, having passed the time it took to pass through the network line and the time it took to propagate through the space on the receiving side. The voice propagating between the speaker and the microphone on the receiving side in this way is called an echo, and can disrupt the call. For this reason, echo suppression technologies such as echo cancellers and echo suppressors have been proposed.

[0003] For example, in the echo suppression device shown in Patent Document 1, when a received signal is reproduced on a speaker, if the level of the received signal is high and distortion may occur in the reproduced sound, a gain that suppresses the signal more effectively than the gain that would be used if no distortion occurs is calculated for each frequency, and a value based on the picked-up signal in the frequency domain is multiplied by the gain.

[0004] Furthermore, for example, the echo suppression device shown in Patent Document 2 calculates, as the second gain coefficient, a value that approaches 0 as the gain coefficient corresponding to the m-times frequency value and its surrounding frequency values, when the power of the reproduced signal at any frequency value is greater than a predetermined threshold and the frequency value is m (m=2, 3, . . . , M) times that frequency value or a frequency value in the vicinity of the m-times frequency value, and calculates the gain coefficient as the second gain coefficient in all other cases.

[0005] However, with the above-mentioned conventional techniques, it is difficult to stably suppress nonlinear echo signals contained in input signals acquired by a microphone, and further improvements are needed. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2017-191992 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-103875 Summary of the Invention

[0007] The present disclosure has been made to solve the above problems, and aims to provide a technology that can stably suppress nonlinear echo signals contained in an input signal acquired by a microphone.

[0008] The echo suppression device according to the present disclosure includes a first linear echo suppression unit that estimates amplitude and phase components of a linear echo signal included in an input signal acquired by a microphone to suppress the linear echo signal from the input signal; a spectral envelope extraction unit that extracts spectral envelope information from at least one of a received signal output to a speaker, the input signal, and an output signal of the first linear echo suppression unit; and a spectral envelope extraction unit that extracts spectral envelope information included in the input signal from at least one of the spectral envelope information extracted from the received signal, the spectral envelope information extracted from the input signal, and the spectral envelope information extracted from the output signal of the first linear echo suppression unit. Non a nonlinear echo estimator for estimating spectral envelope information of a linear echo signal; and a nonlinear echo suppressor for extracting the nonlinear echo signal from an output signal of the first linear echo suppressor using the spectral envelope information of the nonlinear echo signal estimated by the nonlinear echo estimator. signal and a nonlinear echo suppressor that suppresses the nonlinear echo.

[0009] According to the present disclosure, it is possible to stably suppress nonlinear echo signals contained in an input signal acquired by a microphone. [Brief explanation of the drawings]

[0010] [Figure 1] 10A and 10B are diagrams illustrating a microphone signal, an echo canceller output signal, and an echo suppressor output signal when the input signal does not contain a nonlinear echo due to speaker distortion. [Figure 2] 10A and 10B are diagrams illustrating a microphone signal, an echo canceller output signal, and an echo suppressor output signal when a nonlinear echo due to speaker distortion is included in the input signal. [Figure 3] 1 is a diagram illustrating a configuration of a communication device according to a first embodiment of the present disclosure. [Figure 4] FIG. 2 is a diagram showing an example of the spectrum of a received signal and spectral envelope information of the received signal in the first embodiment. [Figure 5] FIG. 2 is a diagram showing an example of the spectrum of a nonlinear echo signal and spectral envelope information of the nonlinear echo signal in the first embodiment. [Figure 6] 4 is a flowchart illustrating an operation of the echo suppression device according to the first embodiment of the present disclosure. [Figure 7] FIG. 1 is a diagram illustrating a configuration of a learning device according to a first embodiment of the present disclosure. [Figure 8] 10 is a diagram showing the results of frequency analysis of an output signal from a conventional echo suppressor and an output signal from an echo suppressor according to the first embodiment. FIG. [Figure 9] FIG. 10 is a diagram illustrating a configuration of a communication device according to a second embodiment of the present disclosure. [Figure 10] FIG. 11 is a diagram illustrating a configuration of a communication device according to a third embodiment of the present disclosure. [Figure 11] FIG. 10 is a diagram illustrating a configuration of a communication device according to a fourth embodiment of the present disclosure. [Figure 12] FIG. 10 is a diagram illustrating a configuration of a learning device according to a fourth embodiment of the present disclosure. [Figure 13]FIG. 13 is a diagram illustrating a configuration of a communication device according to a fifth embodiment of the present disclosure. [Figure 14] FIG. 20 is a diagram illustrating a configuration of a communication device according to a sixth embodiment of the present disclosure. [Figure 15] FIG. 20 is a diagram illustrating a configuration of a communication device according to a seventh embodiment of the present disclosure. [Figure 16] FIG. 13 is a diagram illustrating a configuration of a communication device according to an eighth embodiment of the present disclosure. [Figure 17] 13 is a flowchart illustrating an operation of an echo suppression device according to the eighth embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0011] (Findings that formed the basis of this disclosure) Echo cancellers are a technology that removes echo by estimating the echo signal using an adaptive filter and subtracting the estimated echo signal from the signal picked up by a microphone. Echo is a superposition of the direct sound amplified from the speaker and the reflected sound. Therefore, the transfer characteristics between the speaker and microphone can be expressed by an FIR (Finite Impulse Response) filter. An FIR adaptive filter learns to approximate the transfer characteristics and generates a pseudo-echo signal, which is an estimated value of the echo, by convolving the filter coefficients with the received signal. Proposed adaptive filter learning algorithms include the Least Mean Square (LMS) method, the Normalized LMS (NLMS) method, and methods based on ICA (Independent Component Analysis).

[0012] On the other hand, an echo suppressor is a technology that suppresses echo by estimating the power spectrum of the echo in the frequency domain and subtracting the estimated power spectrum of the echo from the power spectrum of the signal picked up by a microphone. Echo suppressors suppress echo using, for example, the spectral subtraction method or the Wiener filter method. Because the aforementioned echo canceller takes time to train its adaptive filter, residual echo may occur immediately after powering on or when the echo path fluctuates. Furthermore, noise or transmission signals generated by the speaker or microphone may cause the adaptive filter to mis-train, resulting in estimation errors in the pseudo echo signal and an increase in residual echo. For this reason, echo suppressors are generally used after the echo canceller to supplement echo suppression.

[0013] Conventional echo cancellers and echo suppressors estimate echoes using a linear model, which makes it difficult to suppress nonlinear echoes that have been imparted with nonlinear noise such as speaker distortion. In devices used in laptop computers or portable video conferencing systems, large volumes of sound are amplified from small-diameter speakers, so the effects of nonlinear echoes caused by speaker distortion become prominent, potentially making conversations difficult.

[0014] Furthermore, in the above-mentioned Patent Document 1, it is difficult to suppress nonlinear echo signals of frequency components that are not included in the received signal, such as harmonic distortion.

[0015] Furthermore, in the above-mentioned Patent Document 2, it is difficult to suppress wideband distortion components, and it is also difficult to suppress distortion components occurring at frequency values other than integer multiple frequency values.

[0016] In order to solve the above problems, an echo suppression device according to one aspect of the present disclosure includes a first linear echo suppression unit that estimates an amplitude component and a phase component of a linear echo signal included in an input signal acquired by a microphone, thereby suppressing a linear echo signal from the input signal; a spectral envelope extraction unit that extracts spectral envelope information from at least one of a received signal output to a speaker, the input signal, and an output signal of the first linear echo suppression unit; and a spectral envelope extraction unit that extracts spectral envelope information included in the input signal from at least one of the spectral envelope information extracted from the received signal, the spectral envelope information extracted from the input signal, and the spectral envelope information extracted from the output signal of the first linear echo suppression unit. Non a nonlinear echo estimator for estimating spectral envelope information of a linear echo signal; and a nonlinear echo suppressor for extracting the nonlinear echo signal from an output signal of the first linear echo suppressor using the spectral envelope information of the nonlinear echo signal estimated by the nonlinear echo estimator. signal and a nonlinear echo suppressor that suppresses the nonlinear echo.

[0017] According to this configuration, the spectral envelope information of the nonlinear echo signal contained in the input signal is estimated from at least one of the spectral envelope information extracted from the received signal output to the speaker, the spectral envelope information extracted from the input signal, and the spectral envelope information extracted from the output signal of the first linear echo suppressor, and the nonlinear echo signal is suppressed from the output signal of the first linear echo suppressor using the estimated spectral envelope information of the nonlinear echo signal. Therefore, the nonlinear echo signal contained in the input signal acquired by the microphone can be stably suppressed.

[0018] In addition, since the number of dimensions of the extracted spectral envelope information can be made smaller than the number of dimensions of the signal before extraction, it is possible to reduce the amount of memory used when estimating the spectral envelope information of a nonlinear echo signal.Furthermore, since the amount of memory used can be reduced, it is possible to estimate the spectral envelope information of a nonlinear echo signal using multiple pieces of spectral envelope information extracted from multiple signals other than the received signal, thereby improving the estimation accuracy of the spectral envelope information of a nonlinear echo signal.

[0019] Furthermore, the above-described echo suppression device may further include a second linear echo suppression unit that estimates an amplitude component of the residual linear echo signal that was not suppressed by the first linear echo suppression unit, thereby suppressing the residual linear echo signal from the output signal of the nonlinear echo suppression unit.

[0020] According to this configuration, the second linear echo suppressor suppresses the residual linear echo signal from the output signal in which the nonlinear echo signal has been suppressed, thereby enabling the second linear echo suppressor to operate stably and improving the suppression performance of the linear echo signal.

[0021] Furthermore, in the above-described echo suppression device, the nonlinear echo estimation unit may estimate the spectral envelope information of the nonlinear echo signal contained in the input signal from at least one of the spectral envelope information extracted from the received signal, the spectral envelope information extracted from the input signal, and the spectral envelope information extracted from the output signal of the first linear echo suppression unit, using a nonlinear echo model that indicates a relationship between the spectral envelope information of the nonlinear echo signal and at least one of the spectral envelope information extracted from the received signal, the spectral envelope information extracted from the input signal, and the spectral envelope information extracted from the output signal of the first linear echo suppression unit.

[0022] According to this configuration, the spectral envelope information of the nonlinear echo signal contained in the input signal is estimated from at least one of the spectral envelope information extracted from the received signal output to the speaker, the spectral envelope information extracted from the input signal, and the spectral envelope information extracted from the output signal of the first linear echo suppressor, using a nonlinear echo model that indicates the relationship between the spectral envelope information of the nonlinear echo signal and at least one of the spectral envelope information extracted from the received signal output to the speaker, the spectral envelope information extracted from the input signal, and the spectral envelope information extracted from the output signal of the first linear echo suppressor, and the nonlinear echo signal is suppressed from the output signal of the first linear echo suppressor using the estimated spectral envelope information of the nonlinear echo signal. Therefore, the nonlinear echo signal contained in the input signal acquired by the microphone can be stably suppressed.

[0023] Furthermore, in the above echo suppression device, the nonlinear echo model may be trained using, as training data, at least one of the spectral envelope information extracted from the received signal, the spectral envelope information extracted from the input signal, and the spectral envelope information extracted from the output signal of the first linear echo suppression unit, and the spectral envelope information extracted from the output signal of the first linear echo suppression unit that suppresses a linear echo signal from the input signal, with the input being at least one of the spectral envelope information extracted from the received signal, the spectral envelope information extracted from the input signal, and the spectral envelope information extracted from the output signal of the first linear echo suppression unit, and the output being the spectral envelope information of the nonlinear echo signal.

[0024] According to this configuration, the first linear echo suppression unit suppresses only the linear echo signal and does not suppress the nonlinear echo signal, so the signal in which the linear echo signal has been suppressed by the first linear echo suppression unit can be used as the training data as the nonlinear echo signal.

[0025] Furthermore, the spectral envelope information of the nonlinear echo signal is learned using, as training data, at least one of the spectral envelope information extracted from the received signal, the spectral envelope information extracted from the input signal, and the spectral envelope information extracted from the output signal of the first linear echo suppressor. Therefore, it is possible to accurately model the complex distortion caused by the speaker, and to improve the estimation accuracy of the nonlinear echo signal.

[0026] Furthermore, in the above-described echo suppression device, the nonlinear echo estimation unit may estimate the spectral envelope information of the nonlinear echo signal contained in the input signal from the spectral envelope information extracted from the received signal, using the nonlinear echo model that indicates the relationship between the spectral envelope information extracted from the received signal and the spectral envelope information of the nonlinear echo signal.

[0027] According to this configuration, the spectral envelope information of the nonlinear echo signal is estimated from the spectral envelope information extracted from the received signal using a nonlinear echo model that indicates the relationship between the spectral envelope information extracted from the received signal and the spectral envelope information of the nonlinear echo signal. Therefore, the spectral envelope information of the nonlinear echo signal can be easily estimated from the spectral envelope information extracted from the received signal.

[0028] Furthermore, in the above-described echo suppression device, the nonlinear echo estimation unit may estimate the spectral envelope information of the nonlinear echo signal contained in the input signal from the spectral envelope information extracted from the received signal and the spectral envelope information extracted from the input signal, using the nonlinear echo model that indicates the relationship between the spectral envelope information extracted from the received signal and the spectral envelope information extracted from the input signal and the spectral envelope information of the nonlinear echo signal.

[0029] According to this configuration, the spectral envelope information of the nonlinear echo signal is estimated not only from the spectral envelope information extracted from the received signal, but also from the spectral envelope information extracted from the received signal and the spectral envelope information extracted from the input signal, thereby improving the accuracy of estimating the spectral envelope information of the nonlinear echo signal.

[0030] Furthermore, in the above-described echo suppression device, the nonlinear echo estimation unit may estimate the spectral envelope information of the nonlinear echo signal contained in the input signal from the spectral envelope information extracted from the received signal and the spectral envelope information extracted from the output signal of the first linear echo suppression unit, using the nonlinear echo model indicating the relationship between the spectral envelope information extracted from the received signal and the spectral envelope information extracted from the output signal of the first linear echo suppression unit, and the spectral envelope information of the nonlinear echo signal.

[0031] According to this configuration, the spectral envelope information of the nonlinear echo signal is estimated not only from the spectral envelope information extracted from the received signal, but also from the spectral envelope information extracted from the received signal and the spectral envelope information extracted from the output signal of the first linear echo suppression unit, thereby improving the estimation accuracy of the spectral envelope information of the nonlinear echo signal.

[0032] Furthermore, in the above-described echo suppression device, the nonlinear echo estimation unit may estimate the spectral envelope information of the nonlinear echo signal contained in the input signal from the spectral envelope information extracted from the received signal, the spectral envelope information extracted from the input signal, and the spectral envelope information extracted from the output signal of the first linear echo suppression unit, using the nonlinear echo model indicating the relationship between the spectral envelope information extracted from the received signal, the spectral envelope information extracted from the input signal, and the spectral envelope information extracted from the output signal of the first linear echo suppression unit and the spectral envelope information of the nonlinear echo signal.

[0033] According to this configuration, the spectral envelope information of the nonlinear echo signal is estimated not only from the spectral envelope information extracted from the received signal, but also from the spectral envelope information extracted from the received signal, the spectral envelope information extracted from the input signal, and the spectral envelope information extracted from the output signal of the first linear echo suppression unit, thereby improving the accuracy of estimating the spectral envelope information of the nonlinear echo signal.

[0034] Furthermore, in the above-described echo suppression device, the first linear echo suppression unit may include an adaptive filter that generates a pseudo-linear echo signal indicating a component of the received signal included in the input signal by convolving a filter coefficient with the received signal, and a subtraction unit that subtracts the pseudo-linear echo signal from the input signal, and the nonlinear echo estimation unit may estimate spectral envelope information of the nonlinear echo signal included in the input signal from the spectral envelope information extracted from the received signal and the spectral envelope information extracted from the pseudo-linear echo signal from the adaptive filter, using the nonlinear echo model that indicates the relationship between the spectral envelope information extracted from the received signal and the spectral envelope information extracted from the pseudo-linear echo signal from the adaptive filter, and the spectral envelope information of the nonlinear echo signal.

[0035] According to this configuration, the spectral envelope information of the nonlinear echo signal is estimated not only from the spectral envelope information extracted from the received signal, but also from the spectral envelope information extracted from the received signal and the spectral envelope information extracted from the pseudo-linear echo signal from the adaptive filter of the first linear echo suppression unit, thereby improving the estimation accuracy of the spectral envelope information of the nonlinear echo signal.

[0036] Furthermore, in the above-described echo suppression device, the nonlinear echo estimation unit may estimate the spectral envelope information of the nonlinear echo signal contained in the input signal from the spectral envelope information extracted from the input signal, using the nonlinear echo model that indicates the relationship between the spectral envelope information extracted from the input signal and the spectral envelope information of the nonlinear echo signal.

[0037] According to this configuration, the spectral envelope information of the nonlinear echo signal is estimated from the spectral envelope information extracted from the input signal using a nonlinear echo model that shows the relationship between the spectral envelope information extracted from the input signal and the spectral envelope information of the nonlinear echo signal, so that the spectral envelope information of the nonlinear echo signal can be easily estimated from the spectral envelope information extracted from the input signal.

[0038] In the above echo suppression device, the spectral envelope extraction unit may extract spectral envelope information from at least one of the received signal, the input signal, and the output signal of the first linear echo suppression unit by linear predictive analysis.

[0039] With this configuration, spectral envelope information is extracted from at least one of the received signal, the input signal, and the output signal of the first linear echo suppressor by linear predictive analysis, thereby making it possible to compress the amount of information in at least one of the received signal, the input signal, and the output signal of the first linear echo suppressor. Furthermore, with linear predictive analysis, spectral envelope information is extracted that emphasizes the peaks of the original signal, making it possible to accurately represent the spectrum of the original signal even with a small number of dimensions.

[0040] In addition, in the above echo suppression device, the spectral envelope extraction unit may convert at least one linear prediction coefficient of the received signal, the input signal, and the output signal of the first linear echo suppression unit, which have been analyzed by a linear prediction analysis method, into PARCOR (Partial Autocorrelation) coefficients, and extract spectral envelope information represented by the converted PARCOR coefficients.

[0041] This configuration has the advantage that the PARCOR coefficients have a value range of -1 to +1, eliminating the need to normalize the neural network training data. Furthermore, since the PARCOR coefficients do not vary in coefficient sensitivity depending on the number of dimensions, they are less susceptible to the effects of neural network prediction errors than linear prediction coefficients. Furthermore, since the dynamic range of the PARCOR coefficients is fixed, they can be easily converted to fixed-point numbers during implementation.

[0042] Furthermore, the present disclosure can be realized not only as an echo suppression device having the above-described characteristic configuration, but also as an echo suppression method that executes characteristic processing corresponding to the characteristic configuration of the echo suppression device. Furthermore, the present disclosure can also be realized as a computer program that causes a computer to execute characteristic processing included in such an echo suppression method. Therefore, the following other aspects can also achieve the same effects as the above-described echo suppression device.

[0043] An echo suppression method according to another aspect of the present disclosure includes: a first linear echo suppressor estimating an amplitude component and a phase component of a linear echo signal included in an input signal acquired by a microphone, thereby suppressing the linear echo signal from the input signal; a spectral envelope extractor extracting spectral envelope information from at least one of a received signal output to a speaker, the input signal, and an output signal of the first linear echo suppressor; and a nonlinear echo estimator estimating a nonlinear echo signal included in the input signal from at least one of the spectral envelope information extracted from the received signal, the spectral envelope information extracted from the input signal, and the spectral envelope information extracted from the output signal of the first linear echo suppressor. Non a nonlinear echo suppressor for estimating spectral envelope information of the linear echo signal, and a nonlinear echo suppressor for extracting the nonlinear echo signal from the output signal of the first linear echo suppressor by using the spectral envelope information of the nonlinear echo signal estimated by the nonlinear echo estimator; signal to suppress.

[0044] An echo suppression program according to another aspect of the present disclosure includes a first linear echo suppression unit that suppresses a linear echo signal from an input signal acquired by a microphone by estimating an amplitude component and a phase component of the linear echo signal included in the input signal; a spectral envelope extraction unit that extracts spectral envelope information from at least one of a received signal output to a speaker, the input signal, and an output signal of the first linear echo suppression unit; and a spectral envelope extraction unit that extracts spectral envelope information included in the input signal from at least one of the spectral envelope information extracted from the received signal, the spectral envelope information extracted from the input signal, and the spectral envelope information extracted from the output signal of the first linear echo suppression unit. Non a nonlinear echo estimator for estimating spectral envelope information of a linear echo signal; and a nonlinear echo suppressor for extracting the nonlinear echo signal from an output signal of the first linear echo suppressor using the spectral envelope information of the nonlinear echo signal estimated by the nonlinear echo estimator. signal The computer functions as a nonlinear echo suppressor that suppresses the

[0045] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. Note that the following embodiments are examples of specific embodiments of the present disclosure and are not intended to limit the technical scope of the present disclosure.

[0046] (Embodiment 1) First, the causes of nonlinear echoes will be described.

[0047] Nonlinear distortion is a general term for distortion that occurs when the input and output of a system are not proportional. For example, if a two-tone sine wave with frequencies f1 and f2 is input to a system with input / output characteristics in which the output amplitude clips as the input amplitude increases, nonlinear distortion will occur in the amplitude spectrum of the output waveform at frequency components that do not exist in the input signal. Nonlinear distortion can be broadly divided into harmonic distortion that occurs at frequencies that are integer multiples of the input signal, such as 2f1 and 2f2, and intermodulation distortion that occurs at the sum and difference frequencies of the input signals, such as f1 + f2 and f2 - f1.

[0048] In actual systems, nonlinear distortion of the loudspeaker's amplified sound is the cause of nonlinear echo. In commonly used electrodynamic loudspeakers, the displacement of the diaphragm increases in the frequency range near the lowest resonance frequency (f0). Nonlinear distortion occurs due to the nonlinearity of the driving force caused by the voice coil moving beyond the range of the magnetic flux generated by the permanent magnet, or the mechanical nonlinearity of the support system, such as the cone edge or damper. Furthermore, in small-diameter loudspeakers, the sound pressure near the lowest resonance frequency (f0) is sometimes boosted by pre-processing to compensate for the decrease in low-frequency sound pressure. In this case, the displacement of the diaphragm increases, causing further nonlinear distortion.

[0049] Next, the influence of nonlinear echoes on conventional echo suppression techniques will be described, with reference to a system equipped with an echo canceller and an echo suppressor.

[0050] The echo canceller calculates an estimated echo value, i.e., a pseudo echo signal, using an adaptive filter, and removes the echo by subtracting the calculated pseudo echo signal from the microphone signal. In other words, the received signal is x(k), and the coefficients of the adaptive filter are w n (k) and the number of taps of the adaptive filter is N, the pseudo echo y(k) is expressed by the following equation (1).

[0051]

number

[0052] The above equation (1) means that the pseudo echo is expressed by a linear sum in which the phase and amplitude of the received signal are changed, and it cannot express a nonlinear echo regardless of the adaptive algorithm used for coefficient learning.

[0053] The echo suppressor is placed after the echo canceller. The echo suppressor suppresses the residual echo by estimating the power spectrum of the residual echo that was not suppressed by the echo canceller. In the widely used echo suppressor based on the Wiener filter method, the short-time spectrum X(ω) of the received signal and the short-time spectrum Y of the residual echo are calculated as EC Amount of acoustic coupling between (ω) and E (ω) is estimated and the Wiener filter G wiener (ω) is calculated.

[0054]

number

[0055] And the echo suppressor is a Wiener filter G wiener (ω) is expressed as the short-time spectrum Y of the residual echo as shown in the following equation (3). EC By multiplying (ω), the echo-suppressed signal Y ES (ω) is obtained.

[0056] Y ES (ω)=G wiener (ω)Y EC (ω)···(3)

[0057] In other words, the echo suppressor uses the acoustic coupling amount A estimated for each frequency component. E The residual echo is estimated using the received signal X(ω) and the received signal X(ω). Therefore, the echo suppressor cannot estimate frequency components that do not exist in the received signal, such as nonlinear echoes.

[0058] To support the above findings, the inventors conducted an experiment to evaluate the impact of nonlinear echoes. A conventional echo suppression device was used in the evaluation experiment. The conventional echo suppression device includes a speaker that amplifies a received signal, a microphone, an echo canceller that suppresses echo signals from an input signal acquired by the microphone, and an echo suppressor that suppresses echo signals from an output signal from the echo canceller. The evaluation experiment also used 1 / 3 octave band noise with a center frequency of 400 Hz, which is near the lowest resonance frequency f0 of the speaker used for amplification.

[0059] FIG. 1 is a diagram showing a microphone signal, an echo canceller output signal, and an echo suppressor output signal when the input signal does not contain a nonlinear echo due to speaker distortion, and FIG. 2 is a diagram showing a microphone signal, an echo canceller output signal, and an echo suppressor output signal when the input signal contains a nonlinear echo due to speaker distortion.

[0060] 1 and 2, the solid line represents the microphone signal (input signal) output from the microphone, the dashed line represents the echo canceller output signal, and the dashed-dotted line represents the echo suppressor output signal. In Fig. 1 and Fig. 2, the horizontal axis represents frequency, and the vertical axis represents amplitude level.

[0061] In Figure 2, the second to fourth harmonics of the input signal appear, and as mentioned above, this shows that conventional echo cancellers and echo suppressors are completely unable to suppress nonlinear echoes. Furthermore, if we focus on the fundamental tone around 400 Hz in Figures 1 and 2, we can see that the echo canceller suppresses echoes by about 35 dB when no nonlinear echo is included, whereas when a nonlinear echo is included, the amount of echo canceller suppression deteriorates to about 20 dB. This is thought to be because the adaptive filter continues to forcibly update the filter coefficients in an attempt to simulate nonlinear echoes that it is not supposed to be able to represent, causing erroneous learning and resulting in errors in echo estimation.

[0062] An essential problem with conventional echo suppression technology is that it cannot represent nonlinear echoes because it estimates echoes using a linear model. Therefore, the echo suppression device in this embodiment 1 estimates nonlinear echoes using a neural network that can approximate any nonlinear function. There are two possible methods for introducing a neural network: one is to estimate the amplitude and phase of the nonlinear echo and apply it to an echo canceller, and the other is to estimate only the amplitude of the nonlinear echo and apply it to an echo suppressor. The former requires higher estimation accuracy than the latter, and has the problem of increasing the amount of calculation. Therefore, the echo suppression device in this embodiment 1 suppresses nonlinear echoes using an echo suppressor method that can be implemented with low power consumption, low cost, and a small amount of calculation.

[0063] 3 is a diagram showing a configuration of a communication device according to the first embodiment of the present disclosure. The communication device is used in a loudspeaker type hands-free communication system, a loudspeaker type two-way communication conference system, an intercom system, and the like.

[0064] The communication device shown in FIG. 3 includes an echo suppression device 1, an input terminal 11, a speaker 12, a microphone 13, and an output terminal 20.

[0065] The input terminal 11 outputs to the echo suppressing device 1 a received signal received from a communication device (not shown) on the receiving side.

[0066] The speaker 12 outputs the input received signal to the outside. Here, when the voice output from the speaker 12 is picked up by the microphone 13, the voice uttered by the speaker on the receiving side is reproduced from the speaker on the receiving side with a delay, and so-called acoustic echo occurs. Therefore, the echo suppression device 1 suppresses the acoustic echo signal included in the input signal output from the microphone 13. At this time, the acoustic echo signal includes a linear echo signal and a nonlinear echo signal.

[0067] The microphone 13 is placed in a space where the speaker is present, and picks up the speaker's voice. The microphone 13 outputs an input signal indicating the picked-up voice to the echo suppressing device 1.

[0068] The output terminal 20 outputs the input signal in which the linear echo signal and the nonlinear echo signal have been suppressed by the echo suppression device 1.

[0069] The input terminal 11 and the output terminal 20 are connected to a communication unit (not shown). The communication unit transmits an input signal to a call device (not shown) on the receiving side via a network, and receives a call signal from the call device (not shown) on the receiving side via the network. The network is, for example, the Internet.

[0070] The echo suppression device 1 includes an echo canceller 14 , a spectral envelope extraction unit 15 , a nonlinear echo model storage unit 16 , a nonlinear echo estimation unit 17 , a nonlinear echo suppression unit 18 , and an echo suppressor 19 .

[0071] The input terminal 11 outputs a received signal to a speaker 12 , an echo canceller 14 , a spectrum envelope extractor 15 and an echo suppressor 19 .

[0072] The echo canceller 14 suppresses the linear echo signal from the input signal acquired by the microphone 13 by estimating the amplitude component and phase component of the linear echo signal included in the input signal. The echo canceller 14 is an example of a first linear echo suppression unit. The echo canceller 14 suppresses only the linear echo signal included in the input signal output from the microphone 13.

[0073] The echo canceller 14 includes an adaptive filter and a subtraction unit (not shown).

[0074] The adaptive filter generates a pseudo echo signal that indicates the component of the received signal contained in the input signal acquired by the microphone 13 by convolving the filter coefficient with the received signal.

[0075] The subtractor calculates an error signal between the input signal from the microphone 13 and the pseudo echo signal from the adaptive filter, and outputs the calculated error signal to the adaptive filter. The adaptive filter modifies the filter coefficients based on the input error signal, and generates a pseudo echo signal by convolving the modified filter coefficients with the received signal. The adaptive filter modifies the filter coefficients using an adaptive algorithm so as to minimize the error signal. Examples of the adaptive algorithm that can be used include 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).

[0076] The subtraction unit also suppresses the linear echo signal from the input signal by subtracting the pseudo echo signal from the adaptive filter from the input signal from the microphone 13. The subtraction unit then outputs the input signal with the linear echo signal suppressed to the nonlinear echo suppression unit 18.

[0077] The spectral envelope extraction unit 15 extracts spectral envelope information from at least one of the received signal output to the speaker 12, the input signal acquired by the microphone 13, and the output signal of the echo canceller 14. The spectral envelope extraction unit 15 in the first embodiment extracts the spectral envelope information from the received signal output to the speaker 12.

[0078] The spectral envelope extraction unit 15 uses Linear Predictive Coding (LPC) analysis to extract spectral envelope information from at least one of the received signal, the input signal, and the output signal of the echo canceller 14. The spectral envelope extraction unit 15 in the first embodiment extracts spectral envelope information from the received signal using linear predictive analysis. Using linear predictive analysis, the spectral envelope extraction unit 15 predicts future values of the discrete signal as a linear mapping of the values of the sample group up to that point.

[0079] A linear prediction model (LPC model) is a method for calculating spectral envelope information. The linear prediction model predicts a certain sample value s(n) of a speech waveform from n previous sample values, and is expressed by the following equation (4).

[0080]

number

[0081] The spectral envelope extraction unit 15 performs linear prediction analysis on the received signal to calculate linear prediction coefficients of the received signal, and calculates spectral envelope information of the received signal using the calculated linear prediction coefficients. The pth-order linear prediction coefficient α for n sample values can be calculated using the autocorrelation method, the covariance method, or the like. Using the calculated linear prediction coefficient α, the input speech signal can be generated using the following equation (5).

[0082] Y(z)={1 / A(z)}U(z) (5)

[0083] In the above equation (5), Y(z) is the z-transform of the audio signal y(n), 1 / A(z) is a transfer function, and U(z) is the z-transform of the sound source signal u(n) and corresponds to white noise.

[0084] Fig. 4 is a diagram showing an example of the spectrum of a received signal and spectral envelope information of the received signal in the present embodiment 1. In Fig. 4, the horizontal axis represents frequency bins, and the vertical axis represents power. Also in Fig. 4, the solid line represents the spectrum of the received signal, and the dashed line represents the spectral envelope information of the received signal.

[0085] 4 has a number of dimensions of, for example, 6 to 20. The number of dimensions of the spectral envelope information is smaller than the number of dimensions of the received signal. Therefore, the spectral envelope extraction unit 15 can compress the amount of information of the received signal by extracting the spectral envelope information of the received signal.

[0086] Furthermore, the spectral envelope information extracted from the received signal by linear prediction emphasizes the peaks of the received signal, so the spectrum of the received signal can be accurately represented even with a small number of dimensions. Furthermore, as the number of dimensions of linear prediction increases, the spectral envelope information can more precisely represent the spectrum of the received signal.

[0087] The spectral envelope extraction unit 15 outputs the spectral envelope information extracted from the received signal to the nonlinear echo estimation unit 17 .

[0088] In the first embodiment, the spectral envelope extraction unit 15 may convert at least one linear prediction coefficient of the received signal, the input signal, and the output signal of the echo canceller 14, which have been analyzed by linear prediction analysis, into PARCOR (Partial Auto-Correlation) coefficients, and extract spectral envelope information represented by the converted PARCOR coefficients. PARCOR coefficients are known to have better interpolation characteristics than linear prediction coefficients. Furthermore, PARCOR coefficients can be calculated using the Levinson-Durbin-Itakura algorithm. Since the range of PARCOR coefficients is −1 to +1, there is an advantage in that normalization of neural network training data is unnecessary. Furthermore, since PARCOR coefficients do not differ in coefficient sensitivity depending on the number of dimensions, they can be less susceptible to the influence of neural network prediction errors compared to linear prediction coefficients. Furthermore, since the dynamic range of PARCOR coefficients is fixed, they can be easily converted to fixed-point notation during implementation.

[0089] The spectral envelope information may be expressed using line spectral pairs (LSPs) other than linear predictive coefficients and PARCOR coefficients. The spectral envelope extraction unit 15 may convert at least one linear predictive coefficient of the received signal, the input signal, and the output signal of the echo canceller 14, which have been analyzed by linear predictive analysis, into a line spectral pair.

[0090] In the first embodiment, the spectral envelope extraction unit 15 extracts spectral envelope information of at least one of the received signal, the input signal, and the output signal of the echo canceller 14 by linear predictive analysis, but the present disclosure is not particularly limited to this. The spectral envelope extraction unit 15 may also extract spectral envelope information of at least one of the received signal, the input signal, and the output signal of the echo canceller 14 by, for example, cepstrum analysis.

[0091] The nonlinear echo model storage unit 16 stores in advance a nonlinear echo model indicating the relationship between at least one of spectral envelope information extracted from the received signal output to the speaker 12, spectral envelope information extracted from the input signal acquired by the microphone 13, and spectral envelope information extracted from the output signal of the echo canceller 14, and the spectral envelope information of the nonlinear echo signal. Note that the nonlinear echo model storage unit 16 in the first embodiment stores in advance a nonlinear echo model indicating the relationship between the spectral envelope information extracted from the received signal and the spectral envelope information of the nonlinear echo signal. The nonlinear echo model is, for example, a neural network.

[0092] The nonlinear echo model is trained using as training data at least one of the spectral envelope information extracted from the received signal, the spectral envelope information extracted from the input signal, and the spectral envelope information extracted from the output signal of the echo canceller 14, and the spectral envelope information extracted from the output signal of an echo canceller that suppresses a linear echo signal from the input signal, with the input being at least one of the spectral envelope information extracted from the received signal, the spectral envelope information extracted from the input signal, and the spectral envelope information extracted from the output signal of the echo canceller 14, and the output being the spectral envelope information of the nonlinear echo signal. The nonlinear echo model in the first embodiment is trained using as training data the spectral envelope information extracted from the received signal and the spectral envelope information extracted from the output signal of an echo canceller that suppresses a linear echo signal from the input signal, with the input being the spectral envelope information extracted from the received signal, and the output being the spectral envelope information of the nonlinear echo signal.

[0093] The nonlinear echo estimation unit 17 estimates the spectral envelope information of the nonlinear echo signal included in the input signal from at least one of the spectral envelope information extracted from the received signal output to the speaker 12, the spectral envelope information extracted from the input signal acquired by the microphone 13, and the spectral envelope information extracted from the output signal of the echo canceller 14. More specifically, the nonlinear echo estimation unit 17 estimates the spectral envelope information of the nonlinear echo signal included in the input signal from at least one of the spectral envelope information extracted from the received signal, the spectral envelope information extracted from the input signal, and the spectral envelope information extracted from the output signal of the echo canceller 14, using a nonlinear echo model that indicates the relationship between the spectral envelope information of the nonlinear echo signal and at least one of the spectral envelope information extracted from the received signal, the spectral envelope information extracted from the input signal, and the spectral envelope information extracted from the output signal of the echo canceller 14.

[0094] Fig. 5 is a diagram showing an example of the spectrum of a nonlinear echo signal and spectral envelope information of the nonlinear echo signal in the first embodiment. In Fig. 5, the horizontal axis represents frequency bins, and the vertical axis represents power. Also in Fig. 5, the solid line represents the spectrum of the nonlinear echo signal, and the dashed line represents the spectral envelope information of the nonlinear echo signal.

[0095] The number of dimensions of the spectral envelope information shown in Fig. 5 is, for example, 6 to 20. The number of dimensions of the spectral envelope information is smaller than the number of dimensions of the nonlinear echo signal. Therefore, the nonlinear echo estimation unit 17 can reduce the amount of memory used by estimating the spectral envelope information of the nonlinear echo signal from the spectral envelope information extracted from the received signal.

[0096] As described above, in the first embodiment, the received signal and the nonlinear echo signal are expressed by spectral envelope information, thereby reducing the number of dimensions of the input signal and the output signal handled by the nonlinear echo model. On the other hand, the time-domain received signal and the nonlinear echo signal are expressed by the frequency-domain received signal and the nonlinear echo signal, thereby also reducing the number of dimensions of the input signal and the output signal handled by the nonlinear echo model. In this case, the received signal is subjected to a fast Fourier transform, thereby converting the time-domain received signal into a frequency-domain received signal, and the frequency-domain received signal is used as an input signal to the nonlinear echo model, and a frequency-domain nonlinear echo signal is output from the nonlinear echo model.

[0097] However, the number of dimensions of a signal that has undergone fast Fourier transform is, for example, 64, 128, 256, 512, or 1024, whereas the number of dimensions of spectral envelope information is, for example, 6 to 20. In this way, the amount of information can be significantly compressed with spectral envelope information compared to signals that have been transformed into the frequency domain, and the amount of memory used can be significantly reduced.

[0098] Furthermore, the spectral envelope information of the nonlinear echo signal estimated by the nonlinear echo estimation unit 17 emphasizes the peaks of the nonlinear echo signal, so that the spectrum of the nonlinear echo signal can be accurately expressed even with a small number of dimensions. Furthermore, as the number of dimensions of the linear prediction increases, the spectral envelope information can more precisely express the spectrum of the nonlinear echo signal.

[0099] The nonlinear echo estimation unit 17 reads out the nonlinear echo model from the nonlinear echo model storage unit 16. The nonlinear echo estimation unit 17 acquires the spectral envelope information of the nonlinear echo signal from the nonlinear echo model by inputting the spectral envelope information of the received signal output from the spectral envelope extraction unit 15 to the nonlinear echo model. The nonlinear echo estimation unit 17 outputs the spectral envelope information of the nonlinear echo signal estimated using the spectral envelope information of the received signal to the nonlinear echo suppression unit 18.

[0100] The nonlinear echo suppressor 18 suppresses the nonlinear echo signal from the input signal by using the spectral envelope information of the nonlinear echo signal estimated by the nonlinear echo estimator 17. More specifically, the nonlinear echo suppressor 18 suppresses the nonlinear echo signal from the output signal of the echo canceller 14 by using the spectral envelope information of the nonlinear echo signal estimated by the nonlinear echo estimator 17.

[0101] The nonlinear echo suppressor 18 calculates the spectral envelope information x of the estimated nonlinear echo signal based on the following equation (6): NN (k) and the output signal (input signal) y from the echo canceller 14 EC (k) and the Wiener filter G NN Calculate (k).

[0102]

number

[0103] The nonlinear echo suppressor 18 uses a Wiener filter G NN (k) is expressed as the input signal y EC (k) to suppress the nonlinear echo signal. NL-ES Obtain (k).

[0104] y NL-ES (k)=G NN (k)y EC (k) (7)

[0105] The nonlinear echo suppressor 18 outputs the input signal in which only the nonlinear echo signal has been suppressed to the echo suppressor 19 .

[0106] The echo suppressor 19 suppresses the residual linear echo signal by estimating the amplitude component of the residual linear echo signal that was not suppressed by the echo canceller 14. More specifically, the echo suppressor 19 suppresses the residual linear echo signal from the output signal of the nonlinear echo suppressor 18 by estimating the amplitude component of the residual linear echo signal that was not suppressed by the echo canceller 14. The echo suppressor 19 is an example of a second linear echo suppressor.

[0107] The echo suppressor 19 suppresses the residual linear echo signal by the spectral subtraction method or the Wiener filter method. The echo suppressor 19 estimates the acoustic coupling amount for each frequency using the spatial or coherence function of only the echo signal. The echo suppressor 19 calculates a suppression gain using the estimated acoustic coupling amount, the output signal of the nonlinear echo suppressor 18, and the received signal. The echo suppressor 19 suppresses the residual linear echo signal that was not suppressed by the echo canceller 14 by multiplying the output signal of the nonlinear echo suppressor 18 by the calculated suppression gain. The echo suppressor 19 outputs the input signal from which only the residual linear echo signal has been suppressed to the output terminal 20.

[0108] Next, the operation of the echo suppressing device 1 according to the first embodiment of the present disclosure will be described.

[0109] FIG. 6 is a flowchart illustrating the operation of the echo suppressing device 1 according to the first embodiment of the present disclosure.

[0110] First, in step S1, the echo canceller 14 estimates the amplitude and phase components of a linear echo signal contained in the input signal acquired by the microphone 13, thereby suppressing the linear echo signal from the input signal.

[0111] Next, in step S2, the spectrum envelope extraction unit 15 extracts spectrum envelope information from the received signal to be output to the speaker 12.

[0112] Next, in step S3, the nonlinear echo estimation unit 17 estimates the spectral envelope information of the nonlinear echo signal contained in the input signal from the spectral envelope information extracted from the received signal, using a nonlinear echo model that indicates the relationship between the spectral envelope information extracted from the received signal and the spectral envelope information of the nonlinear echo signal.

[0113] Next, in step S 4 , the nonlinear echo suppressor 18 suppresses the nonlinear echo signal from the output signal of the echo canceller 14 using the spectral envelope information of the nonlinear echo signal estimated by the nonlinear echo estimator 17 .

[0114] Next, in step S5, the echo suppressor 19 suppresses the residual linear echo signal from the output signal of the nonlinear echo suppressor 18 by estimating the amplitude component of the residual linear echo signal that was not suppressed by the echo canceller 14. The echo suppressor 19 outputs the input signal, from which only the residual linear echo signal has been suppressed, to the output terminal 20 as a transmitting signal.

[0115] As described above, the spectral envelope information of the nonlinear echo signal contained in the input signal is estimated from at least one of the spectral envelope information extracted from the received signal output to the speaker 12, the spectral envelope information extracted from the input signal acquired by the microphone 13, and the spectral envelope information extracted from the output signal of the echo canceller 14, using a nonlinear echo model that indicates the relationship between the spectral envelope information of the nonlinear echo signal and at least one of the spectral envelope information extracted from the received signal, the spectral envelope information extracted from the input signal, and the spectral envelope information extracted from the output signal of the echo canceller 14, and the nonlinear echo signal is suppressed from the output signal of the echo canceller 14 using the estimated spectral envelope information of the nonlinear echo signal. Therefore, the nonlinear echo signal contained in the input signal acquired by the microphone 13 can be stably suppressed.

[0116] Furthermore, residual linear echo signals are suppressed from the output signal in which nonlinear echo signals have been suppressed by the echo suppressor 19. This makes it possible to stabilize the operation of the echo suppressor 19 and improve the performance of suppressing linear echo signals.

[0117] Furthermore, the number of dimensions of the spectral envelope information extracted from the received signal is smaller than the number of dimensions of the original received signal, and the number of dimensions of the spectral envelope information of the nonlinear echo signal is smaller than the number of dimensions of the nonlinear echo signal. Therefore, by expressing the received signal and the nonlinear echo signal using spectral envelope information, it is possible to reduce memory usage.

[0118] Next, a method for learning the nonlinear echo model in the first embodiment will be described.

[0119] FIG. 7 is a diagram illustrating a configuration of a learning device according to the first embodiment of the present disclosure.

[0120] The learning device shown in FIG. 7 includes a nonlinear echo model creating device 2, an input terminal 31, a speaker 32, and a microphone 33.

[0121] The input terminal 31 receives a call signal from a call device (not shown) on the receiving side. Nonlinear echo model creation device 2 Output to.

[0122] The speaker 32 outputs the received signal to the outside.

[0123] The microphone 33 is placed in a space where the speaker is present, and picks up the speaker's voice. The microphone 33 outputs an input signal representing the picked-up voice to the nonlinear echo model creating device 2.

[0124] The configurations of the input terminal 31, the speaker 32, and the microphone 33 are the same as the configurations of the input terminal 11, the speaker 12, and the microphone 13 in FIG.

[0125] The nonlinear echo model creating device 2 includes an echo canceller 34, spectral envelope extracting units 35 and 36, a nonlinear echo model learning unit 37, and a nonlinear echo model storage unit 38.

[0126] The echo canceller 34 suppresses the linear echo signal from the input signal by estimating the amplitude component and phase component of the linear echo signal included in the input signal acquired by the microphone 33. The configuration of the echo canceller 34 is the same as the configuration of the echo canceller 14 shown in Fig. 3. The echo canceller 34 outputs the input signal with the linear echo signal suppressed to the spectrum envelope extraction unit 35.

[0127] The spectral envelope extraction unit 35 extracts spectral envelope information from the output signal of the echo canceller 34. The spectral envelope extraction unit 35 outputs the spectral envelope information extracted from the output signal of the echo canceller 34 to the nonlinear echo model learning unit 37.

[0128] The spectral envelope extraction unit 36 extracts spectral envelope information from the received signal to be output to the speaker 32. The spectral envelope extraction unit 36 outputs the spectral envelope information extracted from the received signal to the nonlinear echo model learning unit 37.

[0129] The nonlinear echo model learning unit 37 uses as training data at least one of the spectral envelope information extracted from the received signal, the spectral envelope information extracted from the input signal, and the spectral envelope information extracted from the output signal of the echo canceller 34, and the spectral envelope information extracted from the output signal of the echo canceller 34 that suppresses a linear echo signal from the input signal, to learn a nonlinear echo model whose input is at least one of the spectral envelope information extracted from the received signal, the spectral envelope information extracted from the input signal, and the spectral envelope information extracted from the output signal of the echo canceller 34, and whose output is the spectral envelope information of a nonlinear echo signal.

[0130] The nonlinear echo model learning unit 37 in the first embodiment uses, as training data, the spectral envelope information extracted from the received signal and the spectral envelope information extracted from the output signal of the echo canceller 34, which suppresses a linear echo signal from an input signal. When the spectral envelope information extracted from the received signal by the spectral envelope extraction unit 36 is input, the nonlinear echo model learning unit 37 learns a nonlinear echo model so as to output the spectral envelope information of the nonlinear echo signal extracted from the output signal of the echo canceller 34 by the spectral envelope extraction unit 35.

[0131] The nonlinear echo model is a neural network that has been pre-trained using, as training data, the spectral envelope information extracted from the received signal and the spectral envelope information extracted from the output signal of the echo canceller 34. The echo canceller 34 can suppress only linear echo signals. Therefore, the output signal (residual echo signal) of the echo canceller 34 is approximately equal to the nonlinear echo signal. In this way, the nonlinear echo model training unit 37 can model the relationship between the spectral envelope information extracted from the received signal and the spectral envelope information of the nonlinear echo signal.

[0132] Examples of machine learning include supervised learning, which learns the relationship between input and output using training data in which labels (output information) are assigned to the input information; unsupervised learning, which builds data structures from unlabeled inputs only; semi-supervised learning, which handles both labeled and unlabeled data; and reinforcement learning, which learns behaviors that maximize rewards through trial and error. Specific machine learning techniques include neural networks (including deep learning using multilayer neural networks), as well as genetic programming, decision trees, Bayesian networks, and support vector machines (SVMs). Any of the above specific examples can be used in machine learning for nonlinear echo models.

[0133] The nonlinear echo model learning unit 37 stores the learned nonlinear echo model in the nonlinear echo model storage unit .

[0134] The nonlinear echo model storage unit 38 stores the nonlinear echo model learned by the nonlinear echo model learning unit 37 .

[0135] 3 may include a spectral envelope extraction unit 35 and a nonlinear echo model learning unit 37. In this case, the echo suppression device 1 may further include a mode switching unit that switches between a learning mode and an echo suppression mode. When the mode switching unit switches to the learning mode, the echo canceller 14 outputs an output signal to the spectral envelope extraction unit 35. The nonlinear echo model learning unit 37 may learn a nonlinear echo model using, as training data, spectral envelope information extracted from the output signal in which the linear echo signal has been suppressed by the echo canceller 14 and spectral envelope information extracted from the received signal.

[0136] Furthermore, the nonlinear echo model learned by the learning device may be stored in advance in the nonlinear echo model storage unit 16 of the echo suppression device 1. Furthermore, the echo suppression device 1 may receive the nonlinear echo model learned by the learning device and update the nonlinear echo model stored in the nonlinear echo model storage unit 16.

[0137] The nonlinear echo model creating device 2 may further include an echo suppressor. In this case, the echo canceller 34 may suppress the linear echo signal from the input signal by estimating the amplitude component and phase component of the linear echo signal included in the input signal acquired by the microphone 33. The echo canceller 34 may output the input signal with the linear echo signal suppressed to the echo suppressor. The echo suppressor may suppress the residual linear echo signal from the input signal by estimating the amplitude component of the residual linear echo signal not suppressed by the echo canceller 34. The configuration of the echo suppressor is the same as the configuration of the echo suppressor 19 shown in FIG. 3. The echo suppressor may output the input signal with only the residual linear echo signal suppressed from the input signal to the spectral envelope extraction unit 35. The spectral envelope extraction unit 35 may extract spectral envelope information from the output signal of the echo suppressor. The spectral envelope extraction unit 35 echo Spectral envelope information extracted from the output signal of the suppressor may be output to the nonlinear echo model learning unit 37 .

[0138] The nonlinear echo model learning unit 37 calculates a nonlinear echo model based on at least one of the spectral envelope information extracted from the received signal, the spectral envelope information extracted from the input signal, and the spectral envelope information extracted from the output signal of the echo canceller 34, and the output signal of the echo suppressor that suppresses the residual linear echo signal from the output signal of the echo canceller 34 that suppresses the linear echo signal from the input signal. from The extracted spectral envelope information may be used as training data to train a nonlinear echo model in which the input is at least one of the spectral envelope information extracted from the received signal, the spectral envelope information extracted from the input signal, and the spectral envelope information extracted from the output signal of the echo canceller 34, and the output is the spectral envelope information of the nonlinear echo signal.

[0139] Fig. 8 is a diagram showing the results of frequency analysis of the output signal from a conventional echo suppression device and the output signal from echo suppression device 1 of Embodiment 1. In Fig. 8, the horizontal axis represents frequency, and the vertical axis represents amplitude level. In Fig. 8, the solid line represents the input signal from microphone 13, the dashed line represents the output signal from the conventional echo suppression device, and the dash-dotted line represents the output signal from echo suppression device 1 of Embodiment 1. The received signal is 1 / 3 octave band noise with a center frequency of 315 Hz.

[0140] As shown in Fig. 8, the echo suppression device 1 of this embodiment 1 achieves a suppression effect of 15 dB to 20 dB, which exceeds the target value, for harmonic distortion, which is a nonlinear echo signal. Furthermore, the echo suppression device 1 of this embodiment 1 achieves a suppression effect that is approximately 15 dB higher for a 315 Hz linear echo signal, compared to the conventional echo suppression device. This is thought to be because the nonlinear echo signal is suppressed by the nonlinear echo suppressor 18 of this embodiment 1, allowing the estimation of the acoustic coupling amount in the subsequent echo suppressor 19 to operate stably.

[0141] In this way, the echo suppressing device 1 of the first embodiment enables comfortable conversation even with a speaker that generates a lot of distortion, and can contribute to higher quality, smaller size and lower cost of notebook computers, web conferencing systems, mobile phones and the like.

[0142] In addition, by extracting the spectral envelope, the amount of information of the feature can be reduced, which makes it possible to increase the number of learning parameters of the nonlinear echo model. For example, if the nonlinear model is a neural network, it is possible to increase the number of intermediate layers.

[0143] (Embodiment 2) The nonlinear echo estimating unit 17 in the above-described first embodiment estimates the spectral envelope information of the nonlinear echo signal included in the input signal from the spectral envelope information extracted from the received signal, using a nonlinear echo model that indicates the relationship between the spectral envelope information extracted from the received signal and the spectral envelope information of the nonlinear echo signal. In contrast, the nonlinear echo estimating unit in the second embodiment estimates the spectral envelope information of the nonlinear echo signal included in the input signal from the spectral envelope information extracted from the received signal and the spectral envelope information extracted from the input signal, using a nonlinear echo model that indicates the relationship between the spectral envelope information extracted from the received signal and the spectral envelope information extracted from the input signal, and the spectral envelope information of the nonlinear echo signal.

[0144] FIG. 9 is a diagram illustrating a configuration of a communication device according to the second embodiment of the present disclosure.

[0145] 9 includes an echo suppression device 1A, an input terminal 11, a speaker 12, a microphone 13, and an output terminal 20. In the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted.

[0146] The echo suppression device 1A includes an echo canceller 14, spectral envelope extraction units 15 and 21, a nonlinear echo model storage unit 161, a nonlinear echo estimation unit 171, a nonlinear echo suppression unit 18, and an echo suppressor 19.

[0147] The microphone 13 outputs the input signal to the echo canceller 14 and also to the spectrum envelope extraction unit 21 .

[0148] The spectral envelope extraction unit 21 extracts spectral envelope information from the input signal acquired by the microphone 13. The spectral envelope extraction unit 21 extracts the spectral envelope information from the input signal by linear predictive analysis. The configuration of the spectral envelope extraction unit 21 is the same as the configuration of the spectral envelope extraction unit 15. The spectral envelope extraction unit 21 outputs the spectral envelope information extracted from the input signal to the nonlinear echo estimation unit 171.

[0149] The nonlinear echo model storage unit 161 in the second embodiment stores in advance a nonlinear echo model that indicates the relationship between the spectrum envelope information extracted from the received signal output to the speaker 12 and the spectrum envelope information extracted from the input signal acquired by the microphone 13, and the spectrum envelope information of the nonlinear echo signal. The nonlinear echo model is, for example, a neural network.

[0150] The nonlinear echo model in the second embodiment uses, as training data, spectral envelope information extracted from the received signal, spectral envelope information extracted from the input signal, and spectral envelope information extracted from the output signal of an echo canceller that suppresses a linear echo signal from the input signal, and is trained with the spectral envelope information extracted from the received signal and the spectral envelope information extracted from the input signal as input, and the spectral envelope information of the nonlinear echo signal as output.

[0151] In the learning method of the nonlinear echo model in the second embodiment, spectral envelope information extracted from the received signal and spectral envelope information extracted from the input signal are input to the nonlinear echo model learning unit 37 shown in Fig. 7. The nonlinear echo model learning unit 37 in the second embodiment uses, as training data, the spectral envelope information extracted from the received signal, the spectral envelope information extracted from the input signal, and the spectral envelope information extracted from the output signal of the echo canceller 34 that suppresses a linear echo signal from the input signal. When the spectral envelope information extracted from the received signal and the spectral envelope information extracted from the input signal are input, the nonlinear echo model learning unit 37 learns the nonlinear echo model so as to output the spectral envelope information of the nonlinear echo signal extracted from the output signal of the echo canceller 34.

[0152] The nonlinear echo estimation unit 171 estimates the spectral envelope information of the nonlinear echo signal contained in the input signal from the spectral envelope information extracted from the received signal and the spectral envelope information extracted from the input signal, using a nonlinear echo model that indicates the relationship between the spectral envelope information extracted from the received signal and the spectral envelope information extracted from the input signal and the spectral envelope information of the nonlinear echo signal.

[0153] The nonlinear echo estimation unit 171 reads out a nonlinear echo model from the nonlinear echo model storage unit 161. The nonlinear echo estimation unit 171 acquires spectral envelope information of the nonlinear echo signal from the nonlinear echo model by inputting into the nonlinear echo model the spectral envelope information extracted from the received signal output from the spectral envelope extraction unit 15 and the spectral envelope information extracted from the input signal output from the spectral envelope extraction unit 21. The nonlinear echo estimation unit 171 outputs to the nonlinear echo suppression unit 18 the spectral envelope information of the nonlinear echo signal estimated using the spectral envelope information extracted from the received signal and the spectral envelope information extracted from the input signal.

[0154] 6. That is, in the second embodiment, in step S2, the spectral envelope extraction unit 15 extracts spectral envelope information from the received signal output to the speaker 12, and the spectral envelope extraction unit 21 extracts spectral envelope information from the input signal acquired by the microphone 13. Then, in step S3, the nonlinear echo estimation unit 171 estimates the spectral envelope information of the nonlinear echo signal from the spectral envelope information extracted from the received signal and the spectral envelope information extracted from the input signal, using a nonlinear echo model that indicates the relationship between the spectral envelope information extracted from the received signal and the spectral envelope information extracted from the input signal, and the spectral envelope information of the nonlinear echo signal.

[0155] The number of dimensions of the spectral envelope information can be significantly reduced compared to the number of dimensions of the signal before extraction or the number of dimensions of the signal transformed into the frequency domain. Therefore, the number of input signals handled by the nonlinear echo model can be increased without increasing the amount of memory used. In the second embodiment, two signals (spectral envelope information of the received signal and spectral envelope information of the input signal) are input to the nonlinear echo model, so the estimation accuracy of the nonlinear echo signal can be further improved.

[0156] (Embodiment 3) The nonlinear echo estimating unit 17 in the above-described first embodiment estimates the spectral envelope information of the nonlinear echo signal included in the input signal from the spectral envelope information extracted from the received signal, using a nonlinear echo model that indicates the relationship between the spectral envelope information extracted from the received signal and the spectral envelope information of the nonlinear echo signal. In contrast, the nonlinear echo estimating unit in the third embodiment estimates the spectral envelope information of the nonlinear echo signal included in the input signal from the spectral envelope information extracted from the received signal and the spectral envelope information extracted from the output signal of the echo canceller, using a nonlinear echo model that indicates the relationship between the spectral envelope information extracted from the received signal and the spectral envelope information extracted from the output signal of the echo canceller, and the spectral envelope information of the nonlinear echo signal.

[0157] FIG. 10 is a diagram illustrating a configuration of a communication device according to the third embodiment of the present disclosure.

[0158] 10 includes an echo suppression device 1B, an input terminal 11, a speaker 12, a microphone 13, and an output terminal 20. In the third embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted.

[0159] The echo suppression device 1B includes an echo canceller 14, spectral envelope extraction units 15 and 22, a nonlinear echo model storage unit 162, a nonlinear echo estimation unit 172, a nonlinear echo suppression unit 18, and an echo suppressor 19.

[0160] The spectral envelope extraction unit 22 extracts spectral envelope information from the output signal of the echo canceller 14. The spectral envelope extraction unit 22 extracts the spectral envelope information from the output signal of the echo canceller 14 by linear predictive analysis. The configuration of the spectral envelope extraction unit 22 is the same as the configuration of the spectral envelope extraction unit 15. The spectral envelope extraction unit 22 outputs the spectral envelope information extracted from the output signal of the echo canceller 14 to the nonlinear echo estimation unit 172.

[0161] The nonlinear echo model storage unit 162 stores in advance a nonlinear echo model that indicates the relationship between the spectral envelope information extracted from the received signal output to the speaker 12, the spectral envelope information extracted from the output signal of the echo canceller, and the spectral envelope information of the nonlinear echo signal. The nonlinear echo model is, for example, a neural network.

[0162] The nonlinear echo model in the third embodiment uses, as training data, spectral envelope information extracted from the received signal, spectral envelope information extracted from the output signal of an echo canceller that suppresses a linear echo signal from an input signal, and spectral envelope information extracted from the output signal of the echo canceller, and learns with the spectral envelope information extracted from the received signal and the spectral envelope information extracted from the output signal of the echo canceller as input and the spectral envelope information of the nonlinear echo signal as output.

[0163] In the learning method of the nonlinear echo model in the third embodiment, spectral envelope information extracted from the received signal and spectral envelope information extracted from the output signal of the echo canceller 34 are input to the nonlinear echo model learning unit 37 shown in Fig. 7. Then, the nonlinear echo model learning unit 37 in the third embodiment uses, as training data, the spectral envelope information extracted from the received signal, the spectral envelope information extracted from the output signal of the echo canceller 34 that suppresses a linear echo signal from the input signal, and the spectral envelope information extracted from the output signal of the echo canceller 34. When the spectral envelope information extracted from the received signal and the spectral envelope information extracted from the output signal of the echo canceller 34 are input, the nonlinear echo model learning unit 37 learns the nonlinear echo model so as to output the spectral envelope information of the nonlinear echo signal extracted from the output signal of the echo canceller 34.

[0164] The nonlinear echo estimation unit 172 estimates the spectral envelope information of the nonlinear echo signal contained in the input signal from the spectral envelope information extracted from the received signal and the spectral envelope information extracted from the output signal of the echo canceller 14, using a nonlinear echo model that indicates the relationship between the spectral envelope information extracted from the received signal and the spectral envelope information extracted from the output signal of the echo canceller, and the spectral envelope information of the nonlinear echo signal.

[0165] The nonlinear echo estimation unit 172 reads out the nonlinear echo model from the nonlinear echo model storage unit 162. The nonlinear echo estimation unit 172 acquires the spectral envelope information of the nonlinear echo signal from the nonlinear echo model by inputting the spectral envelope information extracted from the received signal output from the spectral envelope extraction unit 15 and the spectral envelope information extracted from the output signal of the echo canceller 14 output from the spectral envelope extraction unit 22 to the nonlinear echo model. The nonlinear echo estimation unit 172 outputs the spectral envelope information of the nonlinear echo signal estimated using the spectral envelope information extracted from the received signal and the spectral envelope information extracted from the output signal of the echo canceller 14 to the nonlinear echo suppression unit 18.

[0166] 6. That is, in the third embodiment, in step S2, the spectral envelope extraction unit 15 extracts spectral envelope information from the received signal output to the speaker 12, and the spectral envelope extraction unit 22 extracts spectral envelope information from the output signal of the echo canceller 14. Then, in step S3, the nonlinear echo estimation unit 172 estimates the spectral envelope information of the nonlinear echo signal from the spectral envelope information extracted from the received signal and the spectral envelope information extracted from the output signal of the echo canceller 14, using a nonlinear echo model that indicates the relationship between the spectral envelope information extracted from the received signal and the spectral envelope information extracted from the output signal of the echo canceller 14, and the spectral envelope information of the nonlinear echo signal.

[0167] In the third embodiment, two signals (spectral envelope information of the received signal and spectral envelope information of the output signal of the echo canceller 14) are input to the nonlinear echo model, so that the estimation accuracy of the nonlinear echo signal can be further improved.

[0168] (Fourth embodiment) The nonlinear echo estimating unit 17 in the above-described first embodiment estimates the spectral envelope information of the nonlinear echo signal included in the input signal from the spectral envelope information extracted from the received signal, using a nonlinear echo model that indicates the relationship between the spectral envelope information extracted from the received signal and the spectral envelope information of the nonlinear echo signal. In contrast, the nonlinear echo estimating unit in the fourth embodiment estimates the spectral envelope information of the nonlinear echo signal included in the input signal from the spectral envelope information extracted from the received signal, the spectral envelope information extracted from the input signal, and the spectral envelope information extracted from the output signal of the echo canceller, using a nonlinear echo model that indicates the relationship between the spectral envelope information extracted from the received signal, the spectral envelope information extracted from the input signal, and the spectral envelope information extracted from the output signal of the echo canceller.

[0169] FIG. 11 is a diagram illustrating a configuration of a communication device according to the fourth embodiment of the present disclosure.

[0170] 11 includes an echo suppression device 1C, an input terminal 11, a speaker 12, a microphone 13, and an output terminal 20. In the fourth embodiment, the same components as those in the first to third embodiments are given the same reference numerals, and the description thereof will be omitted.

[0171] The echo suppression device 1C includes an echo canceller 14, spectral envelope extraction units 15, 21, and 22, a nonlinear echo model storage unit 163, a nonlinear echo estimation unit 173, a nonlinear echo suppression unit 18, and an echo suppressor 19.

[0172] The nonlinear echo model storage unit 163 stores in advance a nonlinear echo model that indicates the relationship between the spectral envelope information extracted from the received signal output to the speaker 12, the spectral envelope information extracted from the input signal acquired by the microphone 13, and the spectral envelope information extracted from the output signal of the echo canceller, and the spectral envelope information of the nonlinear echo signal. The nonlinear echo model is, for example, a neural network.

[0173] The nonlinear echo model in the fourth embodiment uses, as training data, the spectral envelope information extracted from the received signal, the spectral envelope information extracted from the input signal, the spectral envelope information extracted from the output signal of an echo canceller that suppresses a linear echo signal from the input signal, and the spectral envelope information extracted from the output signal of the echo canceller, and learns with the input being the spectral envelope information extracted from the received signal, the spectral envelope information extracted from the input signal, and the spectral envelope information extracted from the output signal of the echo canceller, and the output being the spectral envelope information of the nonlinear echo signal.

[0174] The nonlinear echo estimation unit 173 estimates the spectral envelope information of the nonlinear echo signal contained in the input signal from the spectral envelope information extracted from the received signal, the spectral envelope information extracted from the input signal, and the spectral envelope information extracted from the output signal of the echo canceller 14, using a nonlinear echo model that indicates the relationship between the spectral envelope information extracted from the received signal, the spectral envelope information extracted from the input signal, and the spectral envelope information extracted from the output signal of the echo canceller.

[0175] The nonlinear echo estimation unit 173 reads out a nonlinear echo model from the nonlinear echo model storage unit 163. The nonlinear echo estimation unit 173 acquires spectral envelope information of the nonlinear echo signal from the nonlinear echo model by inputting into the nonlinear echo model the spectral envelope information extracted from the received signal output from the spectral envelope extraction unit 15, the spectral envelope information extracted from the input signal output from the spectral envelope extraction unit 21, and the spectral envelope information extracted from the output signal of the echo canceller 14 output from the spectral envelope extraction unit 22. The nonlinear echo estimation unit 173 outputs to the nonlinear echo suppression unit 18 the spectral envelope information of the nonlinear echo signal estimated using the spectral envelope information extracted from the received signal, the spectral envelope information extracted from the input signal, and the spectral envelope information extracted from the output signal of the echo canceller 14.

[0176] 6. That is, in the fourth embodiment, in step S2, the spectral envelope extraction unit 15 extracts spectral envelope information from the received signal output to the speaker 12, the spectral envelope extraction unit 21 extracts spectral envelope information from the input signal acquired by the microphone 13, and the spectral envelope extraction unit 22 extracts spectral envelope information from the output signal of the echo canceller 14. Then, in step S3, the nonlinear echo estimating unit 172 estimates the spectral envelope information of the nonlinear echo signal from the spectral envelope information extracted from the received signal, the spectral envelope information extracted from the input signal, and the spectral envelope information extracted from the output signal of the echo canceller 14, using a nonlinear echo model that indicates the relationship between the spectral envelope information extracted from the received signal, the spectral envelope information extracted from the input signal, and the spectral envelope information extracted from the output signal of the echo canceller 14, and the spectral envelope information of the nonlinear echo signal.

[0177] Next, a method for learning the nonlinear echo model in the fourth embodiment will be described.

[0178] FIG. 12 is a diagram illustrating a configuration of a learning device according to the fourth embodiment of the present disclosure.

[0179] The learning device shown in FIG. 12 includes a nonlinear echo model creating device 2A, an input terminal 31, a speaker 32, and a microphone 33.

[0180] The nonlinear echo model creating device 2A includes an echo canceller 34, spectral envelope extracting units 35, 36, and 39, a nonlinear echo model learning unit 371, and a nonlinear echo model storage unit 381.

[0181] The spectral envelope extraction unit 39 extracts spectral envelope information from the input signal acquired by the microphone 33. The spectral envelope extraction unit 39 outputs the spectral envelope information extracted from the input signal to the nonlinear echo model learning unit 371.

[0182] In the nonlinear echo model learning method according to the fourth embodiment, the spectral envelope information extracted from the received signal, the spectral envelope information extracted from the input signal, and the spectral envelope information extracted from the output signal of the echo canceller 34 are input to the nonlinear echo model learning unit 371 shown in FIG.

[0183] The nonlinear echo model learning unit 371 uses, as training data, the spectral envelope information extracted from the received signal, the spectral envelope information extracted from the input signal, and the spectral envelope information extracted from the output signal of the echo canceller 34 that suppresses linear echo signals from the input signal, and learns a nonlinear echo model whose input is the spectral envelope information extracted from the received signal, the spectral envelope information extracted from the input signal, and the spectral envelope information extracted from the output signal of the echo canceller 34, and whose output is the spectral envelope information of the nonlinear echo signal.

[0184] In this fourth embodiment, the output signal of the echo canceller 34 includes a first output signal obtained by suppressing a linear echo signal from an input signal that does not contain audio information input by the microphone 33, and a second output signal obtained by suppressing a linear echo signal from an input signal that does contain audio information.

[0185] The nonlinear echo model learning unit 371 uses, as training data, the spectral envelope information extracted from the received signal, the spectral envelope information extracted from the input signal, and the spectral envelope information extracted from the first output signal of the echo canceller 34, which suppresses linear echo signals from input signals that do not contain voice information. When the spectral envelope information extracted from the received signal by the spectral envelope extraction unit 36, the spectral envelope information extracted from the input signal by the spectral envelope extraction unit 39, and the spectral envelope information extracted from the first output signal of the echo canceller 34 by the spectral envelope extraction unit 35 are input, the nonlinear echo model learning unit 371 learns a nonlinear echo model so as to output the spectral envelope information of the nonlinear echo signal extracted from the first output signal of the echo canceller 34 by the spectral envelope extraction unit 35.

[0186] Furthermore, the nonlinear echo model training unit 371 uses, as training data, the spectral envelope information extracted from the received signal, the spectral envelope information extracted from the input signal, the spectral envelope information extracted from the first output signal of the echo canceller 34 which has suppressed a linear echo signal from an input signal which does not contain voice information, and the spectral envelope information extracted from the second output signal of the echo canceller 34 which has suppressed a linear echo signal from an input signal which contains voice information. When the spectral envelope information extracted from the received signal by the spectral envelope extraction unit 36, the spectral envelope information extracted from the input signal by the spectral envelope extraction unit 39, and the spectral envelope information extracted from the second output signal of the echo canceller 34 by the spectral envelope extraction unit 35 are input, the nonlinear echo model training unit 371 trains a nonlinear echo model so as to output the spectral envelope information of the nonlinear echo signal extracted from the first output signal of the echo canceller 34 by the spectral envelope extraction unit 35.

[0187] That is, when the nonlinear echo model training unit 371 receives the spectral envelope information extracted from the received signal, the spectral envelope information extracted from the input signal, and the spectral envelope information extracted from the first output signal of the echo canceller 34 which has suppressed a linear echo signal from an input signal which does not contain voice information, the nonlinear echo model training unit 371 trains a nonlinear echo model so that the spectral envelope information extracted from the first output signal of the echo canceller 34 is output. Furthermore, when the nonlinear echo model training unit 371 receives the spectral envelope information extracted from the received signal, the spectral envelope information extracted from the input signal, and the spectral envelope information extracted from the second output signal of the echo canceller 34 which has suppressed a linear echo signal from an input signal which contains voice information, the nonlinear echo model training unit 371 trains a nonlinear echo model so that the spectral envelope information extracted from the first output signal of the echo canceller 34 is output.

[0188] This makes it possible to predict the first output signal of the echo canceller 34, which suppresses the linear echo signal from the input signal that does not contain audio information, i.e., the nonlinear echo component of the received signal, regardless of whether the input signal acquired by the microphone contains audio information.

[0189] The nonlinear echo model learning unit 371 stores the learned nonlinear echo model in the nonlinear echo model storage unit 381 .

[0190] The nonlinear echo model storage unit 381 stores the nonlinear echo model learned by the nonlinear echo model learning unit 371 .

[0191] 11 may include a nonlinear echo model learning unit 371. In this case, the echo suppression device 1C may further include a mode switching unit that switches between a learning mode and an echo suppression mode. When the mode switching unit switches to the learning mode, the nonlinear echo model learning unit 371 may learn a nonlinear echo model using, as training data, the spectral envelope information extracted from the received signal, the spectral envelope information extracted from the input signal, and the spectral envelope information extracted from the output signal of the echo canceller 14.

[0192] In the fourth embodiment, three signals (spectral envelope information of the received signal, spectral envelope information of the input signal, and spectral envelope information of the output signal of the echo canceller 14) are input to the nonlinear echo model, which can further improve the estimation accuracy of the nonlinear echo signal.

[0193] (Embodiment 5) The nonlinear echo estimating unit 17 in the above-mentioned first embodiment estimates the spectral envelope information of the nonlinear echo signal included in the input signal from the spectral envelope information extracted from the received signal, using a nonlinear echo model that indicates the relationship between the spectral envelope information extracted from the received signal and the spectral envelope information of the nonlinear echo signal.In contrast, the nonlinear echo estimating unit in the fifth embodiment estimates the spectral envelope information of the nonlinear echo signal included in the input signal from the spectral envelope information extracted from the received signal and the spectral envelope information extracted from the pseudo-linear echo signal from the adaptive filter of the echo canceller, using a nonlinear echo model that indicates the relationship between the spectral envelope information extracted from the received signal and the spectral envelope information extracted from the pseudo-linear echo signal from the adaptive filter of the echo canceller, and the spectral envelope information of the nonlinear echo signal.

[0194] FIG. 13 is a diagram illustrating a configuration of a communication device according to the fifth embodiment of the present disclosure.

[0195] 13 includes an echo suppression device 1D, an input terminal 11, a speaker 12, a microphone 13, and an output terminal 20. In the fifth embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted.

[0196] The echo suppression device 1D includes an echo canceller 14, spectral envelope extraction units 15 and 23, a nonlinear echo model storage unit 164, a nonlinear echo estimation unit 174, a nonlinear echo suppression unit 18, and an echo suppressor 19.

[0197] The echo canceller 14 includes an adaptive filter 141 and a subtraction unit 142. The adaptive filter 141 generates a pseudo-linear echo signal indicating the component of the received signal contained in the input signal by convolving a filter coefficient with the received signal. The subtraction unit 142 subtracts the pseudo-linear echo signal from the input signal.

[0198] The spectral envelope extraction unit 23 extracts spectral envelope information from the pseudo-linear echo signal from the adaptive filter 141. The spectral envelope extraction unit 23 outputs the spectral envelope information extracted from the pseudo-linear echo signal to the nonlinear echo estimation unit 174.

[0199] The nonlinear echo model storage unit 164 stores in advance a nonlinear echo model that indicates the relationship between the spectral envelope information extracted from the received signal output to the speaker 12, the spectral envelope information extracted from the pseudo-linear echo signal from the adaptive filter of the echo canceller, and the spectral envelope information of the nonlinear echo signal. The nonlinear echo model is, for example, a neural network.

[0200] The nonlinear echo model in the fifth embodiment uses, as training data, spectral envelope information extracted from the received signal, spectral envelope information extracted from a pseudo-linear echo signal from an adaptive filter of an echo canceller that suppresses a linear echo signal from an input signal, and spectral envelope information extracted from an output signal of the echo canceller, and is trained with the spectral envelope information extracted from the received signal and the spectral envelope information extracted from the pseudo-linear echo signal as inputs and the spectral envelope information of the nonlinear echo signal as output.

[0201] In the learning method of the nonlinear echo model in the fifth embodiment, spectral envelope information extracted from the received signal and spectral envelope information extracted from the pseudo-linear echo signal from the adaptive filter of the echo canceller 34 are input to the nonlinear echo model learning unit 37 shown in Fig. 7. Then, the nonlinear echo model learning unit 37 in the fifth embodiment uses the spectral envelope information extracted from the received signal, the spectral envelope information extracted from the pseudo-linear echo signal from the adaptive filter of the echo canceller 34, and the spectral envelope information extracted from the output signal of the echo canceller 34 as training data. When the spectral envelope information extracted from the received signal and the spectral envelope information extracted from the pseudo-linear echo signal are input, the nonlinear echo model learning unit 37 learns the nonlinear echo model so as to output the spectral envelope information of the nonlinear echo signal extracted from the output signal of the echo canceller 34.

[0202] The nonlinear echo estimation unit 174 estimates the spectral envelope information of the nonlinear echo signal contained in the input signal from the spectral envelope information extracted from the received signal and the spectral envelope information extracted from the pseudo-linear echo signal from the adaptive filter 141, using a nonlinear echo model that indicates the relationship between the spectral envelope information extracted from the received signal and the spectral envelope information extracted from the pseudo-linear echo signal from the adaptive filter, and the spectral envelope information of the nonlinear echo signal.

[0203] The nonlinear echo estimation unit 174 reads out the nonlinear echo model from the nonlinear echo model storage unit 164. The nonlinear echo estimation unit 174 acquires the spectral envelope information of the nonlinear echo signal from the nonlinear echo model by inputting the spectral envelope information extracted from the received signal output from the spectral envelope extraction unit 15 and the spectral envelope information extracted from the pseudo-linear echo signal output from the spectral envelope extraction unit 23 to the nonlinear echo model. The nonlinear echo estimation unit 174 outputs the spectral envelope information of the nonlinear echo signal estimated using the spectral envelope information extracted from the received signal and the spectral envelope information extracted from the pseudo-linear echo signal to the nonlinear echo suppression unit 18.

[0204] 6. That is, in this fifth embodiment, in step S2, the spectrum envelope extraction unit 15 extracts spectrum envelope information from the received signal output to the speaker 12, and the spectrum envelope extraction unit 23 extracts spectrum envelope information from the pseudo-linear echo signal output from the adaptive filter of the echo canceller 14. Then, in step S3, the nonlinear echo estimation unit 174 extracts spectrum envelope information from the received signal and the pseudo-linear echo signal output from the adaptive filter of the echo canceller 14 using a nonlinear echo model that indicates the relationship between the spectrum envelope information extracted from the received signal and the pseudo-linear echo signal from the adaptive filter of the echo canceller 14, and the spectrum envelope information of the nonlinear echo signal. 141 mosquito et al. The spectral envelope information of the nonlinear echo signal is estimated from the spectral envelope information extracted from the pseudo-linear echo signal.

[0205] In the fifth embodiment, two signals (spectral envelope information of the received signal and spectral envelope information of the pseudo-linear echo signal) are input to the nonlinear echo model, so that the estimation accuracy of the nonlinear echo signal can be further improved.

[0206] (Embodiment 6) The nonlinear echo estimating unit 17 in the above-described first embodiment estimates the spectral envelope information of the nonlinear echo signal included in the input signal from the spectral envelope information extracted from the received signal, using a nonlinear echo model that indicates the relationship between the spectral envelope information extracted from the received signal and the spectral envelope information of the nonlinear echo signal. In contrast, the nonlinear echo estimating unit in the sixth embodiment estimates the spectral envelope information of the nonlinear echo signal included in the input signal from the spectral envelope information extracted from the input signal, using a nonlinear echo model that indicates the relationship between the spectral envelope information extracted from the input signal and the spectral envelope information of the nonlinear echo signal.

[0207] FIG. 14 is a diagram illustrating a configuration of a communication device according to the sixth embodiment of the present disclosure.

[0208] 14 includes an echo suppression device 1E, an input terminal 11, a speaker 12, a microphone 13, and an output terminal 20. In the sixth embodiment, the same components as those in the first and second embodiments are denoted by the same reference numerals, and the description thereof will be omitted.

[0209] The echo suppression device 1 E includes an echo canceller 14 , a spectral envelope extraction unit 21 , a nonlinear echo model storage unit 165 , a nonlinear echo estimation unit 175 , a nonlinear echo suppression unit 18 , and an echo suppressor 19 .

[0210] The nonlinear echo model storage unit 165 in the sixth embodiment stores in advance a nonlinear echo model that indicates the relationship between the spectral envelope information extracted from the input signal acquired by the microphone 13 and the spectral envelope information of the nonlinear echo signal. The nonlinear echo model is, for example, a neural network.

[0211] The nonlinear echo model in the sixth embodiment uses, as training data, spectral envelope information extracted from the input signal and spectral envelope information extracted from the output signal of an echo canceller that suppresses a linear echo signal from the input signal, and is trained using the spectral envelope information extracted from the input signal as the input and the spectral envelope information of the nonlinear echo signal as the output.

[0212] In the learning method of the nonlinear echo model in the sixth embodiment, spectral envelope information extracted from an input signal is input to a nonlinear echo model learning unit 37 shown in Fig. 7. The nonlinear echo model learning unit 37 in the sixth embodiment uses, as training data, the spectral envelope information extracted from the input signal and the spectral envelope information extracted from the output signal of an echo canceller 34 that suppresses a linear echo signal from the input signal. When the spectral envelope information extracted from the input signal is input, the nonlinear echo model learning unit 37 learns a nonlinear echo model so as to output the spectral envelope information of the nonlinear echo signal extracted from the output signal of the echo canceller 34.

[0213] The nonlinear echo estimation unit 175 estimates the spectral envelope information of the nonlinear echo signal contained in the input signal from the spectral envelope information extracted from the input signal, using a nonlinear echo model that indicates the relationship between the spectral envelope information extracted from the input signal and the spectral envelope information of the nonlinear echo signal.

[0214] The nonlinear echo estimation unit 175 reads out the nonlinear echo model from the nonlinear echo model storage unit 165. The nonlinear echo estimation unit 175 acquires the spectral envelope information of the nonlinear echo signal from the nonlinear echo model by inputting the spectral envelope information extracted from the input signal output from the spectral envelope extraction unit 21 to the nonlinear echo model. The nonlinear echo estimation unit 175 outputs the spectral envelope information of the nonlinear echo signal estimated using the spectral envelope information extracted from the input signal to the nonlinear echo suppression unit 18.

[0215] Note that the operation of the echo suppression device 1E in the sixth embodiment differs in the processes of steps S2 and S3 shown in Fig. 6. That is, in the sixth embodiment, in step S2, the spectral envelope extraction unit 21 extracts spectral envelope information from the input signal acquired by the microphone 13. Then, in step S3, the nonlinear echo estimation unit 175 estimates the spectral envelope information of the nonlinear echo signal from the spectral envelope information extracted from the input signal, using a nonlinear echo model that indicates the relationship between the spectral envelope information extracted from the input signal and the spectral envelope information of the nonlinear echo signal.

[0216] In the sixth embodiment, the spectral envelope information of the nonlinear echo signal can be estimated only from the spectral envelope information extracted from the input signal acquired by the microphone 13.

[0217] (Embodiment 7) The nonlinear echo estimating unit 17 in the above-described first embodiment estimates the spectral envelope information of the nonlinear echo signal included in the input signal from the spectral envelope information extracted from the received signal, using a nonlinear echo model that indicates the relationship between the spectral envelope information extracted from the received signal and the spectral envelope information of the nonlinear echo signal.In contrast, the nonlinear echo estimating unit in the seventh embodiment estimates the spectral envelope information of the nonlinear echo signal included in the input signal from the spectral envelope information extracted from the output signal of the echo canceller 14, using a nonlinear echo model that indicates the relationship between the spectral envelope information extracted from the output signal of the echo canceller and the spectral envelope information of the nonlinear echo signal.

[0218] FIG. 15 is a diagram illustrating a configuration of a communication device according to the seventh embodiment of the present disclosure.

[0219] 15 includes an echo suppression device 1F, an input terminal 11, a speaker 12, a microphone 13, and an output terminal 20. In the seventh embodiment, the same components as those in the first and third embodiments are denoted by the same reference numerals, and the description thereof will be omitted.

[0220] The echo suppression device 1 F includes an echo canceller 14 , a spectral envelope extraction unit 22 , a nonlinear echo model storage unit 166 , a nonlinear echo estimation unit 176 , a nonlinear echo suppression unit 18 , and an echo suppressor 19 .

[0221] The nonlinear echo model storage unit 166 stores in advance a nonlinear echo model that indicates the relationship between the spectral envelope information extracted from the output signal of the echo canceller and the spectral envelope information of the nonlinear echo signal. The nonlinear echo model is, for example, a neural network.

[0222] The nonlinear echo model in the seventh embodiment uses, as training data, spectral envelope information extracted from the output signal of an echo canceller that suppresses a linear echo signal from an input signal, and spectral envelope information extracted from the output signal of the echo canceller, with the input being the spectral envelope information extracted from the output signal of the echo canceller, and the output being the spectral envelope information of the nonlinear echo signal, for training.

[0223] In the nonlinear echo model learning method of the seventh embodiment, spectral envelope information extracted from the output signal of the echo canceller 34 is input to the nonlinear echo model learning unit 37 shown in Fig. 7. The nonlinear echo model learning unit 37 of the seventh embodiment uses, as training data, the spectral envelope information extracted from the output signal of the echo canceller 34 that suppresses a linear echo signal from the input signal and the spectral envelope information extracted from the output signal of the echo canceller 34. When the spectral envelope information extracted from the output signal of the echo canceller 34 is input, the nonlinear echo model learning unit 37 learns a nonlinear echo model so as to output the spectral envelope information of the nonlinear echo signal extracted from the output signal of the echo canceller 34.

[0224] The nonlinear echo estimation unit 176 estimates the spectral envelope information of the nonlinear echo signal contained in the input signal from the spectral envelope information extracted from the output signal of the echo canceller 14, using a nonlinear echo model that indicates the relationship between the spectral envelope information extracted from the output signal of the echo canceller and the spectral envelope information of the nonlinear echo signal.

[0225] The nonlinear echo estimation unit 176 reads out the nonlinear echo model from the nonlinear echo model storage unit 166. The nonlinear echo estimation unit 176 acquires the spectral envelope information of the nonlinear echo signal from the nonlinear echo model by inputting the spectral envelope information extracted from the output signal of the echo canceller 14 output from the spectral envelope extraction unit 22 to the nonlinear echo model. The nonlinear echo estimation unit 176 outputs the spectral envelope information of the nonlinear echo signal estimated using the spectral envelope information extracted from the output signal of the echo canceller 14 to the nonlinear echo suppression unit 18.

[0226] 6. That is, in the operation of the echo suppression device 1F in the seventh embodiment, in step S2, the spectral envelope extraction unit 22 extracts spectral envelope information from the output signal of the echo canceller 14. Then, in step S3, the nonlinear echo estimation unit 176 estimates the spectral envelope information of the nonlinear echo signal from the spectral envelope information extracted from the output signal of the echo canceller 14, using a nonlinear echo model that indicates the relationship between the spectral envelope information extracted from the output signal of the echo canceller 14 and the spectral envelope information of the nonlinear echo signal.

[0227] In the seventh embodiment, the spectral envelope information of the nonlinear echo signal can be estimated only from the spectral envelope information extracted from the output signal of the echo canceller 14.

[0228] (Embodiment 8) The echo suppressing device 1 in the above-described first embodiment includes an echo suppressor 19. In contrast, the echo suppressing device in the eighth embodiment does not include the echo suppressor 19.

[0229] FIG. 16 is a diagram illustrating a configuration of a communication device according to the eighth embodiment of the present disclosure.

[0230] 16 includes an echo suppression device 1G, an input terminal 11, a speaker 12, a microphone 13, and an output terminal 20. In the eighth embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted.

[0231] The echo suppression device 1G includes an echo canceller 14, a spectral envelope extraction unit 15, a nonlinear echo model storage unit 16, a nonlinear echo estimation unit 17, and a nonlinear echo suppression unit 18.

[0232] The echo suppressing device 1G of the eighth embodiment differs from the echo suppressing device 1 of the first embodiment in that the echo suppressor 19 is not provided.

[0233] The nonlinear echo suppressor 18 outputs to an output terminal 20 the input signal in which only the nonlinear echo signal has been suppressed.

[0234] FIG. 17 is a flowchart illustrating the operation of the echo suppressing device 1G according to the eighth embodiment of the present disclosure.

[0235] The processing in steps S11 to S14 is the same as the processing in steps S1 to S4 shown in FIG. 6, and therefore a description thereof will be omitted.

[0236] Each of the echo suppressing devices according to the second to seventh embodiments may not include the echo suppressor 19, as in the eighth embodiment.

[0237] 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 that component. Each component may be realized by a program execution unit such as a CPU or processor reading and executing a software program recorded on a recording medium such as a hard disk or semiconductor memory. Furthermore, the program may be executed by another independent computer system by recording the program on a recording medium and transferring it, or by transferring the program via a network.

[0238] Some 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 implemented individually on a single chip, or some or all of them may be integrated on a single chip. Furthermore, the integrated circuit is not limited to an LSI, and may be realized using a dedicated circuit or a general-purpose processor. It is also possible to use an FPGA (Field Programmable Gate Array), which can be programmed after LSI manufacturing, or a reconfigurable processor, which allows the connections and settings of circuit cells within the LSI to be reconfigured.

[0239] Furthermore, 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.

[0240] Furthermore, all the numbers used above are merely examples to specifically explain the present disclosure, and the present disclosure is not limited to the numbers used as examples.

[0241] The order in which the steps are performed shown in the above flowchart is merely an example for specifically explaining the present disclosure, and other orders may be used as long as similar effects are obtained. Also, some of the steps may be performed simultaneously (in parallel) with other steps. [Industrial Applicability]

[0242] The technology disclosed herein can stably suppress nonlinear echo signals contained in an input signal acquired by a microphone, and is therefore useful as a technology for suppressing linear echo signals and nonlinear echo signals contained in an input signal acquired by a microphone.

Claims

1. a first linear echo suppressor configured to estimate an amplitude component and a phase component of a linear echo signal included in an input signal acquired by a microphone, thereby suppressing the linear echo signal from the input signal; a spectral envelope extraction unit that extracts spectral envelope information from at least one of a received signal output to a speaker, the input signal, and an output signal of the first linear echo suppression unit; a nonlinear echo estimator that estimates spectral envelope information of a nonlinear echo signal included in the input signal from at least one of spectral envelope information extracted from the received signal, spectral envelope information extracted from the input signal, and spectral envelope information extracted from the output signal of the first linear echo suppressor; a nonlinear echo suppressor that suppresses the nonlinear echo signal from the output signal of the first linear echo suppressor by using spectral envelope information of the nonlinear echo signal estimated by the nonlinear echo estimator; An echo suppression device comprising:

2. further comprising a second linear echo suppressor that estimates an amplitude component of a residual linear echo signal that has not been suppressed by the first linear echo suppressor, thereby suppressing the residual linear echo signal from the output signal of the nonlinear echo suppressor.

2. The echo suppression device according to claim 1.

3. the nonlinear echo estimation unit estimates spectral envelope information of the nonlinear echo signal included in the input signal from at least one of the spectral envelope information extracted from the received signal, the spectral envelope information extracted from the input signal, and the spectral envelope information extracted from the output signal of the first linear echo suppression unit, using a nonlinear echo model that indicates a relationship between at least one of the spectral envelope information extracted from the received signal, the spectral envelope information extracted from the input signal, and the spectral envelope information extracted from the output signal of the first linear echo suppression unit and the spectral envelope information of the nonlinear echo signal; 3. The echo suppression device according to claim 1.

4. the nonlinear echo model uses, as training data, at least one of spectral envelope information extracted from the received signal, spectral envelope information extracted from the input signal, and spectral envelope information extracted from the output signal of the first linear echo suppression unit, and spectral envelope information extracted from the output signal of the first linear echo suppression unit that suppresses a linear echo signal from the input signal, and is trained with an input being at least one of the spectral envelope information extracted from the received signal, spectral envelope information extracted from the input signal, and spectral envelope information extracted from the output signal of the first linear echo suppression unit, and an output being the spectral envelope information of the nonlinear echo signal.

4. The echo suppression device according to claim 3.

5. the nonlinear echo estimation unit estimates spectral envelope information of the nonlinear echo signal included in the input signal from the spectral envelope information extracted from the received signal, using the nonlinear echo model indicating a relationship between the spectral envelope information extracted from the received signal and the spectral envelope information of the nonlinear echo signal.

5. The echo suppression device according to claim 3 or 4.

6. the nonlinear echo estimation unit estimates spectral envelope information of the nonlinear echo signal included in the input signal from the spectral envelope information extracted from the received signal and the spectral envelope information extracted from the input signal, using the nonlinear echo model indicating a relationship between the spectral envelope information extracted from the received signal and the spectral envelope information extracted from the input signal and the spectral envelope information of the nonlinear echo signal.

5. The echo suppression device according to claim 3 or 4.

7. the nonlinear echo estimation unit estimates spectral envelope information of the nonlinear echo signal included in the input signal from the spectral envelope information extracted from the received signal and the spectral envelope information extracted from the output signal of the first linear echo suppression unit, using the nonlinear echo model indicating a relationship between the spectral envelope information extracted from the received signal and the spectral envelope information extracted from the output signal of the first linear echo suppression unit, and the spectral envelope information of the nonlinear echo signal; 5. The echo suppression device according to claim 3 or 4.

8. the nonlinear echo estimation unit estimates spectral envelope information of the nonlinear echo signal included in the input signal from the spectral envelope information extracted from the received signal, the spectral envelope information extracted from the input signal, and the spectral envelope information extracted from the output signal of the first linear echo suppression unit, using the nonlinear echo model indicating a relationship between the spectral envelope information extracted from the received signal, the spectral envelope information extracted from the input signal, and the spectral envelope information extracted from the output signal of the first linear echo suppression unit, and the spectral envelope information of the nonlinear echo signal; 5. The echo suppression device according to claim 3 or 4.

9. the first linear echo suppression unit includes an adaptive filter that generates a pseudo-linear echo signal indicating a component of the received signal included in the input signal by convolving a filter coefficient with the received signal, and a subtraction unit that subtracts the pseudo-linear echo signal from the input signal; the nonlinear echo estimation unit estimates spectral envelope information of the nonlinear echo signal included in the input signal from the spectral envelope information extracted from the received signal and the spectral envelope information extracted from the pseudo-linear echo signal from the adaptive filter, using the nonlinear echo model indicating a relationship between the spectral envelope information extracted from the received signal and the spectral envelope information extracted from the pseudo-linear echo signal from the adaptive filter, and the spectral envelope information of the nonlinear echo signal.

5. The echo suppression device according to claim 3 or 4.

10. the nonlinear echo estimation unit estimates spectral envelope information of the nonlinear echo signal included in the input signal from the spectral envelope information extracted from the input signal, using the nonlinear echo model indicating a relationship between the spectral envelope information extracted from the input signal and the spectral envelope information of the nonlinear echo signal.

5. The echo suppression device according to claim 3 or 4.

11. the spectral envelope extraction unit extracts spectral envelope information from at least one of the received signal, the input signal, and the output signal of the first linear echo suppression unit by linear predictive analysis; The echo suppression device according to any one of claims 1 to 10.

12. the spectral envelope extraction unit converts at least one linear prediction coefficient of the received signal analyzed by a linear prediction analysis method, the input signal, and the output signal of the first linear echo suppression unit into a PARCOR (partial autocorrelation) coefficient, and extracts spectral envelope information represented by the converted PARCOR coefficient; The echo suppression device according to any one of claims 1 to 10.

13. a first linear echo suppressor estimating an amplitude component and a phase component of a linear echo signal included in an input signal acquired by a microphone, thereby suppressing the linear echo signal from the input signal; a spectral envelope extraction unit extracting spectral envelope information from at least one of a received signal output to a speaker, the input signal, and an output signal of the first linear echo suppression unit; a nonlinear echo estimating unit estimating spectral envelope information of a nonlinear echo signal included in the input signal from at least one of spectral envelope information extracted from the received signal, spectral envelope information extracted from the input signal, and spectral envelope information extracted from the output signal of the first linear echo suppressing unit; a nonlinear echo suppressor suppressing the nonlinear echo signal from the output signal of the first linear echo suppressor by using spectral envelope information of the nonlinear echo signal estimated by the nonlinear echo estimator; Echo suppression method.

14. a first linear echo suppressor configured to estimate an amplitude component and a phase component of a linear echo signal included in an input signal acquired by a microphone, thereby suppressing the linear echo signal from the input signal; a spectral envelope extraction unit that extracts spectral envelope information from at least one of a received signal output to a speaker, the input signal, and an output signal of the first linear echo suppression unit; a nonlinear echo estimator that estimates spectral envelope information of a nonlinear echo signal included in the input signal from at least one of spectral envelope information extracted from the received signal, spectral envelope information extracted from the input signal, and spectral envelope information extracted from the output signal of the first linear echo suppressor; causing a computer to function as a nonlinear echo suppressor that suppresses the nonlinear echo signal from the output signal of the first linear echo suppressor, using the spectral envelope information of the nonlinear echo signal estimated by the nonlinear echo estimator; Echo suppression program.

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