DEREVERBERATION APPARATUS, DEREVERBERATION METHOD, DEREVERBERATION PROGRAM, AND RECORDING MEDIUM

• US 20110002473A1
• Filed: 02/27/2009
• Published: 01/06/2011
• Est. Priority Date: 03/03/2008
• Status: Active Grant

• Current Assignee: Nippon Telegraph and Telephone Corporation
• Original Assignee: Nippon Telegraph and Telephone Corporation
• Inventors: Miyoshi, Masato, Nakatani, Tomohiro, Yoshioka, Takuya, Kinoshita, Keisuke
• Granted Patent: US 8,467,538 B2
• Time in Patent Office: Days
• US Class Current: 381/66
• CPC Class Codes: G10L 2021/02082 the noise being echo, reverberation of the speech
• CPC Class Codes: G10L 21/02 Speech enhancement, e.g. noise reduction or echo cancellation reducing echo effects in line transmission systems H04B3/20; echo suppression in hands-free telephones H04M9/08
• CPC Class Codes: G10L 21/0208 Noise filtering
• CPC Class Codes: G10L 21/0232 Processing in the frequency domain
• CPC Class Codes: H04S 7/305 Electronic adaptation of stereophonic audio signals to reverberation of the listening space H04S7/301 takes precedence

Abstract

A sound source model storage section stores a sound source model that represents an audio signal emitted from a sound source in the form of a probability density function. An observation signal, which is obtained by collecting the audio signal, is converted into a plurality of frequency-specific observation signals each corresponding to one of a plurality of frequency bands. Then, a dereverberation filter corresponding to each frequency band is estimated by using the frequency-specific observation signal for the frequency band on the basis of the sound source model and a reverberation model that represents a relationship for each frequency band among the audio signal, the observation signal and the dereverberation filter. A frequency-specific target signal corresponding to each frequency band is determined by applying the dereverberation filter for the frequency band to the frequency-specific observation signal for the frequency band, and the resulting frequency-specific target signals are integrated.

Claims

1. A dereverberation apparatus that removes a reverberation signal from an observation signal by applying a dereverberation filter to the observation signal, the observation signal being obtained by collecting an audio signal emitted from a sound source, comprising:

a sound source model storage section that stores a sound source model that represents the audio signal in the form of a probability density function;

a dividing section that divides the observation signal into a plurality of frequency-specific observation signals each corresponding to one of a plurality of frequency bands;

an estimating section that determines a dereverberation filter for a corresponding frequency band by using the frequency-specific observation signal for the corresponding frequency band on the basis of the sound source model and a reverberation model that represents a relationship among the audio signal, the observation signal and the dereverberation filter for the corresponding frequency band;

a removing section that determines a frequency-specific target signal for a corresponding frequency band by applying the dereverberation filter for the corresponding frequency band determined by the estimating section to the frequency-specific observation signal for the corresponding frequency band; and

an integrating section that integrates the frequency-specific target signals.

2. The dereverberation apparatus according to claim 1, wherein the reverberation model is an autoregressive model that represents a current observation signal in the form of a signal obtained by adding the audio signal to a signal obtained by applying the dereverberation filter to a previous observation signal having a predetermined delay.

3. The dereverberation apparatus according to claim 1 or 2, wherein the sound source model is a time-varying complex normal distribution model that has an average of 0 and has no correlation between frequency bands.

4. The dereverberation apparatus according to claim 3, wherein the estimating section estimates a variance of the frequency-specific target signals and estimates the dereverberation filter by using a covariance matrix of the frequency-specific observation signals normalized with the estimated variance of the frequency-specific target signals.

10. A computer-readable recording medium in which a program that makes a computer operate as the dereverberation apparatus according to claim 1 is recorded.

5. A dereverberation method that removes a reverberation signal from an observation signal by applying a dereverberation filter to the observation signal, the observation signal being obtained by collecting an audio signal emitted from a sound source,

wherein a sound source model storage section stores a sound source model that represents the audio signal in the form of a probability density function, and the dereverberation method comprises:

a dividing step of dividing the observation signal into a plurality of frequency-specific observation signals each corresponding to one of a plurality of frequency bands;

an estimating step of determining dereverberation filters each corresponding to one of the plurality of frequency bands by using the frequency-specific observation signal for the one of the plurality of frequency bands on the basis of the sound source model and a reverberation model that represents a relationship among the audio signal, the observation signal and the dereverberation filter for each of the plurality of frequency bands;

a removing step of determining frequency-specific target signals each corresponding to one of the plurality of frequency bands by applying the dereverberation filter for the one of the plurality of frequency bands determined in the estimating step to the frequency-specific observation signal for the one of the plurality of frequency bands; and

an integrating step of integrating the frequency-specific target signals.

6. The dereverberation method according to claim 5, wherein the reverberation model is an autoregressive model that represents a current observation signal in the form of a signal obtained by adding the audio signal to a signal obtained by applying the dereverberation filter to a previous observation signal having a predetermined delay.

7. The dereverberation method according to claim 5 or 6, wherein the sound source model is a time-varying complex normal distribution model that has an average of 0 and has no correlation between frequency bands.

8. The dereverberation method according to claim 7, wherein the estimating step comprises a process of estimating a variance of the frequency-specific target signals, and the dereverberation filter is estimated by using a covariance matrix of the frequency-specific observation signals normalized with the estimated variance of the frequency-specific target signals.

9. (canceled)