# US 2017/0287501 A1 · Noise suppressing apparatus, speech recognition apparatus, and noise suppressing method

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- Number: US 2017/0287501 A1
- Document ID: US20170287501A1
- Status: Published application
- Kind: A1
- Application number: 15/468,373
- Filed: 2017-03-24
- Published: 2017-10-05
- Earliest claimed: 2016-03-31
- Assignees: Fujitsu Limited
- Applicants: Fujitsu Limited
- Inventors: Chikako Matsumoto
- Web page: https://patentgrep.com/patent/US20170287501A1

## CPC

- G10L 21/0232: Processing in the frequency domain
- G10L 21/028: using properties of sound source
- G10L 15/20: Speech recognition techniques specially adapted for robustness in adverse environments, e.g. in noise, of stress induced speech (G10L21/02 takes precedence)
- G10L 25/78: Detection of presence or absence of voice signals (switching of direction of transmission by voice frequency in two-way loud-speaking telephone systems H04M9/10)
- G10L 25/87: Detection of discrete points within a voice signal
- G10L 2021/02165: {Two microphones, one receiving mainly the noise signal and the other one mainly the speech signal}
- G10L 2021/02166: {Microphone arrays; Beamforming}
- H04R 3/005: {for combining the signals of two or more microphones (specially adapted for hearing aids H04R25/407)}
- H04R 2201/403: Linear arrays of transducers
- H04R 2430/03: Synergistic effects of band splitting and sub-band processing
- H04R 2430/20: Processing of the output signals of the acoustic transducers of an array for obtaining a desired directivity characteristic (H04R2203/12 takes precedence)
- H04R 2499/13: Acoustic transducers and sound field adaptation in vehicles
- G10L: SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING
- H04R: LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; ELECTRIC HEARING AIDS; PUBLIC ADDRESS SYSTEMS (producing sounds with frequency not determined by supply frequency G10K)

## Abstract

A noise suppressing apparatus calculates a phase difference on the basis of a first and second sound signal obtained by a microphone array; calculates a first sound arrival rate on the basis of a first phase difference area and the phase difference and a second sound arrival rate on the basis of a second phase difference area and the phase difference; calculates a dissimilarity that represents a level of difference between the first sound arrival rate and the second sound arrival rate; determines whether the pickup target sound is included in the first sound signal on the basis of the dissimilarity; and determines a suppression coefficient to be applied to the frequency spectrum of the first sound signal, on the basis of a result of the determination of whether the pickup target sound is included and on the basis of the phase difference.

## Claims

### Claim 1

A noise suppressing apparatus that suppresses noise included in a sound signal, the noise suppressing apparatus comprising:
a memory; and
a processor configured to be connected to the memory and to perform processing of suppressing the noise included in the sound signal, wherein
the processing of suppressing the noise includes:
calculating a phase difference on the basis of frequency spectra of a first sound signal and a second sound signal obtained by picking up a pickup target sound using a microphone array;
calculating a first sound arrival rate on the basis of a first phase difference area and the phase difference and calculating a second sound arrival rate on the basis of a second phase difference area and the phase difference, wherein the first phase difference area is set on the basis of a direction of arrival of the pickup target sound which arrives at the microphone array, and the second phase difference area is different from the first phase difference area;
calculating a dissimilarity that represents a level of difference between the first sound arrival rate and the second sound arrival rate;
determining whether the pickup target sound is included in the first sound signal on the basis of the dissimilarity; and
determining a suppression coefficient to be applied to the frequency spectrum with respect to the first sound signal, on the basis of a result of the determination of whether the pickup target sound is included and on the basis of the phase difference.

### Claim 2 (depends on 1)

The noise suppressing apparatus according to claim 1, wherein
the processor further sets the second phase difference area on the basis of a relationship between a direction of arrival of the noise, the direction of arrival of the pickup target sound, and the first phase difference area.

### Claim 3 (depends on 2)

The noise suppressing apparatus according to claim 2, wherein
the processor sets the second phase difference area which is adjacent to the first phase difference area.

### Claim 4 (depends on 2)

The noise suppressing apparatus according to claim 2, wherein
the processor sets the second phase difference area which is situated away from the first phase difference area.

### Claim 5 (depends on 2)

The noise suppressing apparatus according to claim 2, wherein
the processor sets the second phase difference area which has a portion overlapping the first phase difference area.

### Claim 6 (depends on 2)

The noise suppressing apparatus according to claim 2, wherein
the processor sets the second phase difference area which is included in the first phase difference area.

### Claim 7 (depends on 1)

The noise suppressing apparatus according to claim 1, wherein
the processor calculates, as the dissimilarity, a value obtained by dividing the first sound arrival rate by the second sound arrival rate.

### Claim 8 (depends on 1)

The noise suppressing apparatus according to claim 1, wherein
the processor calculates, as the dissimilarity, a value obtained by subtracting the second sound arrival rate from the first sound arrival rate.

### Claim 9 (depends on 1)

The noise suppressing apparatus according to claim 1, wherein
the processor calculates the suppression coefficient on the basis of the phase difference when the pickup target sound is included in the first sound signal, and determines, to be a suppression coefficient that is to be applied to the frequency spectrum, a minimum value of the suppression coefficient calculated on the basis of the phase difference when the pickup target sound is not included in the first sound signal.

### Claim 10 (depends on 1)

The noise suppressing apparatus according to claim 1, wherein
the processor further stores, in the memory, the result of the determination of whether the pickup target sound is included, wherein
when the processor determines whether the pickup target sound is included in the first sound signal which is a current processing target, the processor
reads the determination result stored in the memory,
determines, on the basis of the dissimilarity, whether the pickup target sound is included in the first sound signal which is the current processing target when the pickup target sound is not included in the first sound signal which is prior to the first sound signal which is the current processing target, and
determines, on the basis of the first sound arrival rate, whether the pickup target sound is included in the first sound signal which is the current processing target when the pickup target sound is included in the first sound signal which is prior to the first sound signal which is the current processing target.

### Claim 11

A speech recognition apparatus that suppresses noise included in a sound signal and performs speech recognition processing on a sound signal in which the noise has been suppressed, the speech recognition apparatus comprising:
a memory; and
a processor configured to be connected to the memory and to perform processing of suppressing the noise included in the sound signal, wherein
the processing of suppressing the noise includes:
calculating a phase difference on the basis of frequency spectra of a first sound signal and a second sound signal obtained by picking up a pickup target sound using a microphone array;
calculating a first sound arrival rate on the basis of a first phase difference area and the phase difference and calculating a second sound arrival rate on the basis of a second phase difference area and the phase difference, wherein the first phase difference area is set on the basis of a direction of arrival of the pickup target sound which arrives at the microphone array, and the second phase difference area is different from the first phase difference area;
calculating a dissimilarity that represents a level of difference between the first sound arrival rate and the second sound arrival rate;
determining whether the pickup target sound is included in the first sound signal on the basis of the dissimilarity;
determining a suppression coefficient to be applied to the frequency spectrum with respect to the first sound signal, on the basis of a result of the determination of whether the pickup target sound is included and on the basis of the phase difference;
applying the determined suppression coefficient to the frequency spectrum; and
transforming the frequency spectrum to which the suppression coefficient has been applied into a sound signal.

### Claim 12

A noise suppressing method for suppressing noise included in a sound signal, the noise suppressing method comprising:
calculating, by a computer, a phase difference on the basis of frequency spectra of a first sound signal and a second sound signal obtained by picking up a pickup target sound using a microphone array;
calculating, by the computer, a first sound arrival rate on the basis of a first phase difference area and the phase difference and calculating, by the computer, a second sound arrival rate on the basis of a second phase difference area and the phase difference, wherein the first phase difference area is set on the basis of a direction of arrival of the pickup target sound which arrives at the microphone array, and the second phase difference area is different from the first phase difference area;
calculating, by the computer, a dissimilarity that represents a level of difference between the first sound arrival rate and the second sound arrival rate;
determining, by the computer, whether the pickup target sound is included in the first sound signal on the basis of the dissimilarity; and
determining, by the computer, a suppression coefficient to be applied to the frequency spectrum with respect to the first sound signal, on the basis of a result of the determination of whether the pickup target sound is included and on the basis of the phase difference.