US5012519A
Expired / Lapsed
US
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Noise reduction system
Assignee: DSP Group Inc
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Filing: 1990-01-05
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Granted: 1991-04-30
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Expires: 2010-01-05
Abstract
Abstract Noise in a speech-plus-noise input signal is suppressed by splitting the input signal into spectral channels and decreasing the gain in the each channel which has a low signal-to-noise ratio (SNR). A voice operated switch (VOX) acts to detect noise-only input to gate a background noise (input signal) estimator and also to gate a residual noise (output signal) estimator. The gain in each of the channels is controlled by the current value (a posteriori) input signal SNR estimate, modified by the prior value (a priori) input signal SNR estimate, and smoothed as a function of the residual (output noise signal) estimate.
Inventors
- 👤 Shabtai Adlersberg
- 👤 Yoram Stettiner
- 👤 Mendel Aizner
- 👤 Alberto Berstein
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-06 20:13
CPC Classifications
G; G10; G10L; G10L21/00; G10L21/02; G10L21/0208; G10L21/0216; G10L2021/02168; G10L21/0232
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
142 words
A digital processing method for reducing the noise in noisy speech signals, including the steps of: (a) generating background noise estimates from noisy speech and storing said background noise estimates; (b) generating adaptive current noise estimates from current noisy speech signals and stored background noise estimates; (c) generating current gain estimates from adaptive current noise estimates and past speech estimates; and (d) using current gain estimates and current noisy speech to obtain current speech estimates, wherein said step of using adaptive current noise estimates and past speech estimates to obtain current gain estimates includes the step of limiting the lower limit of the gain estimate to eliminate musical noise, and wherein said step of generating adaptive current noise estimates includes employing results of a speech/no speech decision from information obtained from current signal input to distinguish said noisy speech from background noise.
Claim 2
Dependent Claim
142 words
A digital processing method for reducing the noise in noisy speech signals, including the steps of: (a) generating background noise estimates from noisy speech and storing said background noise estimates; (b) generating adaptive current noise estimates from current noisy speech signals and stored background noise estimates; (c) generating current gain estimates from adaptive current noise estimates and past speech estimates; and (d) using current gain estimates and current noisy speech to obtain current speech estimates, wherein said step of using adaptive current noise estimates and past speech estimates to obtain current gain estimates includes the step of limiting the lower limit of the gain estimate to eliminate musical noise, and wherein said step of generating adaptive current noise estimates includes employing results of a speech/no speech decision from information obtained from current signal input to distinguish said noisy speech from background noise.
Claim 3
Dependent Claim
50 words
A digital processing method according to claim 1 and wherein said step of using current gain estimates and current noisy speech to obtain current speech estimates comprise the step of applying an automatic gain control algorithm to estimated speech in order to restore the original energy envelope of the speech.
Claim 4
Dependent Claim
18 words
The digital method of claims 1 or 2 and wherein said current noise estimates are background noise estimates.
Claim 5
Dependent Claim
25 words
The invention of claim 1 further including the step of using a speech, no speech decision to select an algorithm when generating decision directed estimates.
Claim 6
Dependent Claim
67 words
A digital processing method for reducing the noise in noisy speech signal, comprising the steps of: (a) generating amplitude estimates from noisy speech; (b) generating residual noise estimates from said amplitude estimates by operation of a voice operated switch; and (c) generating adaptive residual noise estimates from said amplitude estimates when speech is not present; and (d) using said adaptive residual noise estimates for smoothing speech signals.
Claim 7
Dependent Claim
67 words
A digital processing method for reducing the noise in noisy speech signal, comprising the steps of: (a) generating amplitude estimates from noisy speech; (b) generating residual noise estimates from said amplitude estimates by operation of a voice operated switch; and (c) generating adaptive residual noise estimates from said amplitude estimates when speech is not present; and (d) using said adaptive residual noise estimates for smoothing speech signals.
Claim 8
Independent Claim
149 words
A method for reducing the noise in noisy signals containing speech, said method comprising the steps of: (a) generating, from Fourier expansion coefficients of said noisy signals, background noise estimates, and storing said background noise estimates; (b) generating thereafter, from Fourier expansion coefficients of said signals and said stored background noise estimates, adaptive current noise estimates; (c) generating thereafter, from said adaptive current noise estimates and past speech estimates, current gain estimates; and (d) producing thereafter, from said current gain estimates and current digitized noisy signals, current speech estimates, said current speech estimates for use thereafter as past speech estimates, wherein said step (c) includes the step of limiting the lower limit of said gain estimate to eliminate musical noise, and wherein said step (b) includes applying a speech/no speech decision to said noisy signals containing speech to identify said current speech estimates with a signal segment containing speech.
Claim 9
Independent Claim
149 words
A method for reducing the noise in noisy signals containing speech, said method comprising the steps of: (a) generating, from Fourier expansion coefficients of said noisy signals, background noise estimates, and storing said background noise estimates; (b) generating thereafter, from Fourier expansion coefficients of said signals and said stored background noise estimates, adaptive current noise estimates; (c) generating thereafter, from said adaptive current noise estimates and past speech estimates, current gain estimates; and (d) producing thereafter, from said current gain estimates and current digitized noisy signals, current speech estimates, said current speech estimates for use thereafter as past speech estimates, wherein said step (c) includes the step of limiting the lower limit of said gain estimate to eliminate musical noise, and wherein said step (b) includes applying a speech/no speech decision to said noisy signals containing speech to identify said current speech estimates with a signal segment containing speech.
Claim 10
Independent Claim
95 words
A method for reducing noise in noisy signals containing speech, said noisy signals being divided into time invariant segments, said method including the steps of: (a) generating, from Fourier expansion coefficients of said segments of said noisy signals, amplitude estimates; (b) thereafter generating, from said amplitude estimates, (i) residual noise estimates from said amplitude estimates where speech is present in a current segment, and (ii) adaptive residual noise estimates where speech is not present in a current segment; and (e) smoothing said noisy signal containing speech with said adaptive residual noise estimates to suppress noise.
Claim 11
Independent Claim
95 words
A method for reducing noise in noisy signals containing speech, said noisy signals being divided into time invariant segments, said method including the steps of: (a) generating, from Fourier expansion coefficients of said segments of said noisy signals, amplitude estimates; (b) thereafter generating, from said amplitude estimates, (i) residual noise estimates from said amplitude estimates where speech is present in a current segment, and (ii) adaptive residual noise estimates where speech is not present in a current segment; and (e) smoothing said noisy signal containing speech with said adaptive residual noise estimates to suppress noise.
Claim 12
Dependent Claim
138 words
A digital processing method for reducing the noise in noisy speech signals, including the steps of: (a) generating, from Fourier expansion coefficients of segments of said noisy speech signals as amplitude estimates; (b) generating background noise estimates from said amplitude estimates, including employing results of a speech/no speech decision (Y/N) from information obtained from current signal input to distinguish signals containing speech from background noise; (c) generating first signal-to-noise estimates from said background noise estimates and said amplitude estimates (a posteriori SNR); (d) generating decision directed signal-to-noise estimates recursively from said background noise estimates updated on the basis of previous speech amplitude estimates (a priori SNR); (e) generating current gain estimates from said first signal-to-noise estimate and said decision directed signal-to-noise estimates; and (e) using current gain estimates and current noisy speech to obtain current speech amplitude estimates.
Claim 13
Dependent Claim
138 words
A digital processing method for reducing the noise in noisy speech signals, including the steps of: (a) generating, from Fourier expansion coefficients of segments of said noisy speech signals as amplitude estimates; (b) generating background noise estimates from said amplitude estimates, including employing results of a speech/no speech decision (Y/N) from information obtained from current signal input to distinguish signals containing speech from background noise; (c) generating first signal-to-noise estimates from said background noise estimates and said amplitude estimates (a posteriori SNR); (d) generating decision directed signal-to-noise estimates recursively from said background noise estimates updated on the basis of previous speech amplitude estimates (a priori SNR); (e) generating current gain estimates from said first signal-to-noise estimate and said decision directed signal-to-noise estimates; and (e) using current gain estimates and current noisy speech to obtain current speech amplitude estimates.
Claim 14
Dependent Claim
30 words
The method according to claim 8 wherein said step of using current estimates further includes the step of limiting the gain estimates to gain limited estimates to eliminate musical noise.
Claim 15
Dependent Claim
49 words
The method according to claim 8 further including the steps of employing said current speech amplitude estimates using current estimates and results of a speech/no speech decision (Y/N) from information obtained from current signal input to generate a threshold signal for adaptive residual noise for obtaining smoothed amplitude estimates.
References Cited (Backward Citations)
US3431355A
Cited
US3403224A
Cited
US3743787A
Cited
US3878337A
Cited
US3855423A
Cited
US3989897A
Cited
US4000369A
Cited
US4048443A
Cited
US4227046A
Cited
US4133976A
Cited
US4283601A
Cited
US4286116A
Cited
US4227049A
Cited
US4380824A
Cited
US4573188A
Cited
US4538295A
Cited
US4628529A
Cited
US4630304A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1994-04-29 | 1994-10-29 | 1995-04-30 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1998-04-29 | 1998-10-29 | 1999-04-30 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2002-04-29 | 2002-10-29 | 2003-04-30 | $7700.00 | Window Closed / Lapsed |