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US 8,942,975 B2Granted
Noise suppression in a Mel-filtered spectral domain
AssigneeBroadcom Corporation
InventorJonas Borgstrom
Life of this patent
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Abstract
Techniques are described herein that suppress noise in a Mel-filtered spectral domain. For example, a window may be applied to a representation of a speech signal in a time domain. The windowed representation in the time domain may be converted to a subsequent representation of the speech signal in the Mel-filtered spectral domain. A noise suppression operation may be performed with respect to the subsequent representation to provide noise-suppressed Mel coefficients.
Claims20
A method comprising:
- applying a window to a first representation of a speech signal in a time domain to provide a windowed representation of the speech signal;
- converting the windowed representation of the speech signal in the time domain to a second representation of the speech signal in a frequency domain;
- converting the second representation of the speech signal in the frequency domain to a third representation of the speech signal in a filtered spectral domain, wherein the third representation of the speech signal in the filtered spectral domain includes a plurality of Mel coefficients;
- performing, by one or more processors, a noise suppression operation with respect to the third representation of the speech signal in the filtered spectral domain to provide a noise-suppressed representation of the speech signal that includes a plurality of noise-suppressed coefficients, wherein the noise suppression operation comprises:
- determining a mean frame energy of the third representation of the speech signal, the mean frame energy being equal to a sum of the plurality of Mel coefficients divided by a number of the plurality of Mel coefficients;
- and
- for each Mel coefficient of the plurality of Mel coefficients that is less than a noise floor threshold, setting that Mel coefficient to be equal to the noise floor threshold, the noise floor threshold being equal to the mean frame energy multiplied by a designated constant that is less than one.
4 more elements
An automatic speech recognition system comprising:
- one or more processors;
- and
- a memory containing program code, which, when executed by at least one of the one or more processors, is configured to perform operations, the operations comprising:
- applying a window to a first representation of a speech signal in a time domain to provide a windowed representation of the speech signal;
- converting the windowed representation of the speech signal in the time domain to a second representation of the speech signal in a frequency domain, the conversion module further configured to convert the second representation of the speech signal in the frequency domain to a third representation of the speech signal in a filtered spectral domain, wherein the third representation of the speech signal in the filtered spectral domain includes a plurality of Mel coefficients;
- performing a noise suppression operation with respect to the third representation of the speech signal in the filtered spectral domain to provide a noise-suppressed representation of the speech signal that includes a plurality of noise-suppressed coefficients, wherein the noise suppression operation comprises:
- determining a mean frame energy of the third representation of the speech signal, the mean frame energy being equal to a sum of the plurality of Mel coefficients divided by a number of the plurality of Mel coefficients;
- and
- updating each Mel coefficient of the plurality of Mel coefficients that is less than a noise floor threshold to be equal to the noise floor threshold, the noise floor threshold being equal to the mean frame energy multiplied by a designated constant that is less than one.
6 more elements
A computer-readable storage device having computer program logic recorded thereon for enabling a processor-based system to perform noise suppression in a filtered spectral domain, the computer-readable storage device comprising:
- a first program logic that enables the processor-based system to apply a window to a first representation of a speech signal in a time domain to provide a windowed representation of the speech signal;
- a second program logic that enables the processor-based system to convert the windowed representation of the speech signal in the time domain to a second representation of the speech signal in a frequency domain;
- a third program logic that enables the processor-based system to convert the second representation of the speech signal in the frequency domain to a third representation of the speech signal in the filtered spectral domain, wherein the third representation of the speech signal in the filtered spectral domain includes a plurality of Mel coefficients;
- a fourth program logic that enables the processor-based system to perform a noise suppression operation with respect to the third representation of the speech signal in the filtered spectral domain to provide a noise-suppressed representation of the speech signal that includes a plurality of noise-suppressed coefficients, wherein the noise suppression operation comprises:
- a fifth program logic that enables the processor-based system to determine a mean frame energy of the third representation of the speech signal, the mean frame energy being equal to a sum of the plurality of Mel coefficients divided by a number of the plurality of Mel coefficients;
- and
- a sixth program logic that enables the processor-based system to update each Mel coefficient of the plurality of Mel coefficients that is less than a noise floor threshold to be equal to the noise floor threshold, the noise floor threshold being equal to the mean frame energy multiplied by a designated constant that is less than one.
4 more elements
Dependencies are inferred from the claim text.