Echo suppressing device, echo suppressing method, and non-transitory computer readable recording medium storing echo suppressing program

1 . An echo suppressing device comprising:

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 to suppress the linear echo signal from the input signal;

a spectrum envelope extraction unit that extracts spectrum envelope information from at least one of a reception signal to be output to a loudspeaker, the input signal, and an output signal of the first linear echo suppression unit;

a nonlinear echo estimation unit that estimates spectrum envelope information of a nonlinear echo signal included in the input signal from at least one of spectrum envelope information extracted from the reception signal, spectrum envelope information extracted from the input signal, and spectrum envelope information extracted from the output signal of the first linear echo suppression unit; and

a nonlinear echo suppression unit that suppresses the nonlinear echo signal from the output signal of the first linear echo suppression unit by using the spectrum envelope information of the nonlinear echo signal estimated by the nonlinear echo estimation unit.

2 . The echo suppressing device according to claim 1 , further comprising:

a second linear echo suppression unit that estimates an amplitude component of a residual linear echo signal that has not been suppressed by the first linear echo suppression unit to suppress the residual linear echo signal from the output signal of the nonlinear echo suppression unit.

3 . The echo suppressing device according to claim 1 , wherein

using a nonlinear echo model indicating a relationship between at least one of the spectrum envelope information extracted from the reception signal, the spectrum envelope information extracted from the input signal, and the spectrum envelope information extracted from the output signal of the first linear echo suppression unit, and the spectrum envelope information of the nonlinear echo signal, the nonlinear echo estimation unit estimates spectrum envelope information of the nonlinear echo signal included in the input signal from at least one of the spectrum envelope information extracted from the reception signal, the spectrum envelope information extracted from the input signal, and the spectrum envelope information extracted from the output signal of the first linear echo suppression unit.

4 . The echo suppressing device according to claim 3 , wherein

the nonlinear echo model is learned by using, as teacher data, at least one of the spectrum envelope information extracted from the reception signal, the spectrum envelope information extracted from the input signal, and the spectrum envelope information extracted from the output signal of the first linear echo suppression unit, and the spectrum envelope information extracted from the output signal of the first linear echo suppression unit that suppresses the linear echo signal from the input signal, using, as an input, at least one of the spectrum envelope information extracted from the reception signal, the spectrum envelope information extracted from the input signal, and the spectrum envelope information extracted from the output signal of the first linear echo suppression unit, and using the spectrum envelope information of the nonlinear echo signal as an output.

5 . The echo suppressing device according to claim 3 , wherein

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

6 . The echo suppressing device according to claim 3 , wherein

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

7 . The echo suppressing device according to claim 3 , wherein

using the nonlinear echo model indicating a relationship between the spectrum envelope information extracted from the reception signal and the spectrum envelope information extracted from the output signal of the first linear echo suppression unit, and the spectrum envelope information of the nonlinear echo signal, the nonlinear echo estimation unit estimates spectrum envelope information of the nonlinear echo signal included in the input signal from the spectrum envelope information extracted from the reception signal and the spectrum envelope information extracted from the output signal of the first linear echo suppression unit.

8 . The echo suppressing device according to claim 3 , wherein

using the nonlinear echo model indicating a relationship between the spectrum envelope information extracted from the reception signal, the spectrum envelope information extracted from the input signal and the spectrum envelope information extracted from the output signal of the first linear echo suppression unit, and the spectrum envelope information of the nonlinear echo signal, the nonlinear echo estimation unit estimates spectrum envelope information of the nonlinear echo signal included in the input signal from the spectrum envelope information extracted from the reception signal, the spectrum envelope information extracted from the input signal, and the spectrum envelope information extracted from the output signal of the first linear echo suppression unit.

9 . The echo suppressing device according to claim 3 , wherein

the first linear echo suppression unit includes an adaptive filter that generates a pseudo linear echo signal indicating a component of the reception signal included in the input signal by convoluting a filter coefficient and the reception signal, and a subtractor that subtracts the pseudo linear echo signal from the input signal, and

using the nonlinear echo model indicating a relationship between the spectrum envelope information extracted from the reception signal and spectrum envelope information extracted from the pseudo linear echo signal from the adaptive filter, and the spectrum envelope information of the nonlinear echo signal, the nonlinear echo estimation unit estimates spectrum envelope information of the nonlinear echo signal included in the input signal from the spectrum envelope information extracted from the reception signal and the spectrum envelope information extracted from the pseudo linear echo signal from the adaptive filter.

10 . The echo suppressing device according to claim 3 , wherein

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

11 . The echo suppressing device according to claim 1 , wherein

the spectrum envelope extraction unit extracts spectrum envelope information from at least one of the reception signal, the input signal, and the output signal of the first linear echo suppression unit by a linear predictive coding analysis method.

12 . The echo suppressing device according to claim 1 , wherein

the spectrum envelope extraction unit converts at least one linear predictive coding coefficient of the reception signal, the input signal, and the output signal of the first linear echo suppression unit analyzed by a linear predictive coding analysis method into a partial auto-correlation (PARCOR) coefficient, and extracts spectrum envelope information represented by the converted PARCOR coefficient.

13 . An echo suppressing method comprising:

estimating, by a first linear echo suppression unit, an amplitude component and a phase component of a linear echo signal included in an input signal acquired by a microphone to suppress the linear echo signal from the input signal;

extracting, by a spectrum envelope extraction unit, spectrum envelope information from at least one of a reception signal to be output to a loudspeaker, the input signal, and an output signal of the first linear echo suppression unit;

estimating, by a nonlinear echo estimation unit, spectrum envelope information of a nonlinear echo signal included in the input signal from at least one of spectrum envelope information extracted from the reception signal, spectrum envelope information extracted from the input signal, and spectrum envelope information extracted from the output signal of the first linear echo suppression unit; and

suppressing, by a nonlinear echo suppression unit, the nonlinear echo signal from the output signal of the first linear echo suppression unit by using the spectrum envelope information of the nonlinear echo signal estimated by the nonlinear echo estimation unit.

14 . A non-transitory computer readable recording medium storing an echo suppressing program causing a computer to function as:

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 to suppress the linear echo signal from the input signal;

a spectrum envelope extraction unit that extracts spectrum envelope information from at least one of a reception signal to be output to a loudspeaker, the input signal, and an output signal of the first linear echo suppression unit;

a nonlinear echo estimation unit that estimates spectrum envelope information of a nonlinear echo signal included in the input signal from at least one of spectrum envelope information extracted from the reception signal, spectrum envelope information extracted from the input signal, and spectrum envelope information extracted from the output signal of the first linear echo suppression unit; and

a nonlinear echo suppression unit that suppresses the nonlinear echo signal from the output signal of the first linear echo suppression unit by using the spectrum envelope information of the nonlinear echo signal estimated by the nonlinear echo estimation unit.