US6098038A
Expired / Lapsed
US
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Method and system for adaptive speech enhancement using frequency specific signal-to-noise ratio estimates
Assignee: Oregon Health & Science University
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Filing: 1996-09-27
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Granted: 2000-08-01
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Expires: 2016-09-27
Abstract
Abstract A method and system for adaptively filtering a speech signal in order to suppress noise in the signal. The method includes decomposing the signal into multiple frequency subbands, each having a center frequency, estimating a signal-to-noise ratio for each subband, and providing multiple filters, each filter designed for one of a number of selected signal-to-noise ratio independent of the center frequencies of the subbands. The method also includes selecting a filter for filtering each subband, where the filter selected depends on the signal-to-noise ratio estimated for the subband, filtering each subband according to the filter selected, and combining the filtered subbands to provide an estimated filtered speech signal. The system includes appropriate hardware and software for performing the method.
Inventors
- 👤 Hynek Hermansky
- 👤 Carlos M. Avendano
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 10:40
CPC Classifications
G; G10; G10L; G10L21/00; G10L21/02; G10L21/0208
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
108 words
A method for adaptively filtering a speech signal to suppress noise therein, the method comprising: decomposing the speech signal into a plurality of frequency subbands, each subband having a center frequency; estimating a signal-to-noise ratio for each subband; providing a plurality of filters, each filter designed for one of a plurality of selected signal-to-noise ratios independent of the center frequencies of the plurality of subbands; selecting one of the plurality of filters for each subband, wherein the filter selected depends on the signal-to-noise ratio estimated for the subband; filtering each subband according to the filter selected; and combining the filtered subbands to provide an estimated filtered speech signal.
Claim 2
Independent Claim
108 words
A method for adaptively filtering a speech signal to suppress noise therein, the method comprising: decomposing the speech signal into a plurality of frequency subbands, each subband having a center frequency; estimating a signal-to-noise ratio for each subband; providing a plurality of filters, each filter designed for one of a plurality of selected signal-to-noise ratios independent of the center frequencies of the plurality of subbands; selecting one of the plurality of filters for each subband, wherein the filter selected depends on the signal-to-noise ratio estimated for the subband; filtering each subband according to the filter selected; and combining the filtered subbands to provide an estimated filtered speech signal.
Claim 3
Dependent Claim
24 words
The method of claim 1 wherein decomposing the signal into a plurality of frequency subbands comprises performing a short-time Fourier transform on the signal.
Claim 4
Dependent Claim
27 words
The method of claim 2 wherein decomposing the signal into a plurality of frequency subbands further comprises computing a magnitude of each subband and a signal phase.
Claim 5
Dependent Claim
21 words
The method of claim 3 wherein estimating a signal-to-noise ratio for each subband comprises computing a histogram of the subband magnitudes.
Claim 6
Dependent Claim
29 words
The method of claim 1 wherein providing a plurality of filters comprises computing each filter based on parallel recordings of a clean speech signal and a noisy speech signal.
Claim 7
Dependent Claim
53 words
The method of claim 5 wherein providing a plurality of filters comprises: decomposing the noisy speech signal into a plurality of frequency subbands; determining a magnitude response at every subband for the plurality of selected signal-to-noise ratios; and averaging the magnitude responses determined for each one of the plurality of selected signal-to-noise ratios.
Claim 8
Dependent Claim
18 words
The method of claim 6 wherein each of the plurality of filters comprises a finite impulse response filter.
Claim 9
Dependent Claim
14 words
The method of claim 7 wherein the plurality of filters comprises a filter bank.
Claim 10
Dependent Claim
25 words
The method of claim 3 further comprising: compressing the magnitude of each subband prior to filtering; and de-compressing the magnitude of each subband after filtering.
Claim 11
Independent Claim
111 words
A system for adaptively filtering a speech signal to suppress noise therein, the system comprising: means for decomposing the speech signal into a plurality of frequency subbands, each subband having a center frequency; means for estimating a signal-to-noise ratio for each subband; a plurality of filters for filtering the subbands, each filter designed for one of a plurality of selected signal-to-noise ratios independent of the center frequencies of the plurality of subband; means for selecting one of the plurality of filters for each subband, wherein the filter selected depends on the signal-to-noise ratio estimated for the subband; and means for combining the filtered subbands to provide an estimated filtered speech signal.
Claim 12
Independent Claim
111 words
A system for adaptively filtering a speech signal to suppress noise therein, the system comprising: means for decomposing the speech signal into a plurality of frequency subbands, each subband having a center frequency; means for estimating a signal-to-noise ratio for each subband; a plurality of filters for filtering the subbands, each filter designed for one of a plurality of selected signal-to-noise ratios independent of the center frequencies of the plurality of subband; means for selecting one of the plurality of filters for each subband, wherein the filter selected depends on the signal-to-noise ratio estimated for the subband; and means for combining the filtered subbands to provide an estimated filtered speech signal.
Claim 13
Dependent Claim
29 words
The system of claim 10 wherein the means for decomposing the signal into a plurality of frequency subbands comprises means for performing a short-time Fourier transform on the signal.
Claim 14
Dependent Claim
32 words
The system of claim 11 wherein the means for decomposing the signal into a plurality of frequency subbands further comprises means for computing a magnitude of each subband and a signal phase.
Claim 15
Dependent Claim
26 words
The system of claim 12 wherein the means for estimating a signal-to-noise ratio for each subband comprises means for computing a histogram of the subband magnitudes.
Claim 16
Dependent Claim
28 words
The system of claim 10 further comprising means for computing the plurality of filters based on parallel recordings of a clean speech signal and a noisy speech signal.
Claim 17
Dependent Claim
62 words
The system of claim 14 wherein the means for computing the plurality of filters comprises: means for decomposing the noisy speech signal into a plurality of frequency subbands; means for determining a magnitude response at every subband for the plurality of selected signal-to-noise ratios; and means for averaging the magnitude responses determined for each one of the plurality of selected signal-to-noise ratios.
Claim 18
Dependent Claim
18 words
The system of claim 15 wherein each of the plurality of filters comprises a finite impulse response filter.
Claim 19
Dependent Claim
14 words
The system of claim 16 wherein the plurality of filters comprises a filter bank.
Claim 20
Dependent Claim
29 words
The system of claim 12 further comprising: means for compressing the magnitude of each subband prior to filtering; and means for de-compressing the magnitude of each subband after filtering.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2003-08-01 | 2004-01-31 | 2004-08-01 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2007-08-01 | 2008-01-31 | 2008-08-01 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2011-08-01 | 2012-01-31 | 2012-08-01 | $7700.00 | Window Closed / Lapsed |