Noise suppression system
First Claim
1. An improved noise suppression system for attenuating the background noise from a noisy input signal to produce a noise-suppressed output signal, said noise suppression system comprising:
- means for separating the input signal into a plurality of pre-processed signals representative of selected frequency channels;
means for modifying an operating parameter of each of said plurality of pre-processed signals provided by said signal separating means to provide a plurality of post-processed signals; and
means responsive to said plurality of pre-processed signals and said plurality of post-processed signals for generating a modification signal for application to said modifying means to enable the operating parameter to be modified.
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Accused Products
Abstract
An improved noise suppression system (400) is disclosed which performs speech quality enhancement upon speech-plus-noise signal available at the input (205) to generate a clean speech signal at the output (265) by spectral gain modification. The noise suppression system of the present invention includes a background noise estimator (420) which generates and stores an estimate of the background noise power spectral density based upon pre-processed speech (215), as determined by the detected minima of the post-processed speech energy level. This post-processed speech (255) may be obtained directly from the output of the noise suppression system, or may be simulated by multiplying the pre-processed speech energy (225) by the channel gain values of the modification signal (245). This technique of implementing post-processed signal to generate the background noise estimate (325) provides a more accurate measurement of the background noise energy since it is based upon much cleaner speech signal. As a result, the present invention performs acoustic noise suppression in high ambient noise backgrounds with significantly less voice quality degradation.
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Citations
51 Claims
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1. An improved noise suppression system for attenuating the background noise from a noisy input signal to produce a noise-suppressed output signal, said noise suppression system comprising:
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means for separating the input signal into a plurality of pre-processed signals representative of selected frequency channels; means for modifying an operating parameter of each of said plurality of pre-processed signals provided by said signal separating means to provide a plurality of post-processed signals; and means responsive to said plurality of pre-processed signals and said plurality of post-processed signals for generating a modification signal for application to said modifying means to enable the operating parameter to be modified. - View Dependent Claims (5, 6, 7, 8)
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2. An improved noise suppression system for attenuating the background noise from a noisy input signal to produce a noise-suppressed output signal, said noise suppression system comprising:
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means for separating the input signal into a plurality of pre-processed signals representative of selected frequency channels; means for modifying an operating parameter of each of said plurality of pre-processed signals provided by said signal separating means to provide a plurality of post-processed signals; means for generating a control signal representative of said post-processed signals; and means responsive to said plurality of pre-processed signals and said control signal for generating a modification signal for application to said modifying means to enable the operating parameter to be modified. - View Dependent Claims (3, 4)
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9. An improved noise suppression system for attenuating the background noise from a noisy input signal to produce a noise-suppressed output signal, said noise suppression system comprising:
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means for separating the input signal into a plurality of pre-processed signals representative of selected frequency channels; means for modifying the gain of each of said plurality of pre-processed signals in response to estimates of the signal-to-noise ratio (SNR) in each individual channel to provide a plurality of post-processed signals; and means for generating said SNR estimates in each individual channel based upon the current signal energy estimate of the pre-processed signal in each individual channel and the previous noise energy estimate of the pre-processed signal in each individual channel as determined by the detected minima of said plurality of post-processed signals. - View Dependent Claims (14, 17, 19)
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10. An improved noise suppression system for attenuating the background noise from a noisy input signal to produce a noise-suppressed output signal, said noise suppression system comprising:
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means for separating the input signal into a plurality of pre-processed signals representative of selected frequency channels; means for generating an estimate of the signal-to-noise ratio (SNR) in each individual channel based upon the current signal energy estimate of the pre-processed signal in each individual channel and the previous noise energy estimate of the pre-processed signal in each individual channel as determined by the detected minima of a simulated output signal energy level, said simulated output signal being obtained by multiplying said plurality of pre-processed signals by a predetermined gain value; means for producing said predetermined gain value in response to said SNR estimates; and means for modifying the gain of each of said plurality of pre-processed signals in response to said predetermined gain value to provide a plurality of post-processed signals. - View Dependent Claims (11, 12, 13, 15, 16, 18, 20, 21)
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22. An improved noise suppression system for attenuating the background noise from a noisy pre-processed input signal to produce a noise-suppressed post-processed output signal by spectral gain modification, said noise suppression system comprising:
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signal dividing means for separating the pre-processed input signal into a plurality of selected frequency bands, thereby producing a plurality of pre-processed channels; channel energy estimation means for generating an estimate of the energy in each of said plurality of pre-processed channels; background noise estimation means for generating and storing estimates of the background noise energy based upon said channel energy estimates, and for periodically detecting the minima of the post-processed signal energy level obtained from the output of said noise suppression system such that said background noise estimates are updated only during said minima; channel SNR estimation means for generating an estimate of the signal-to-noise ratio (SNR) of each individual channel based upon said channel energy estimates and said background noise estimates; channel gain controlling means for providing channel gain values corresponding to said channel SNR estimates; channel gain modifying means for adjusting the gain of each of said plurality of pre-processed channels provided by said signal dividing means according to said channel gain values, thereby producing a plurality of post-processed channels; and channel combination means for recombining said plurality of post-processed channels to produce said post-processed output signal. - View Dependent Claims (24, 25, 26, 27, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38)
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23. An improved noise suppression system for attenuating the background noise from a noisy pre-processed input signal to produce a noise-suppressed post-processed output signal by spectral gain modification, said noise suppression system comprising:
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signal dividing means for separating the pre-processed input signal into a plurality of selected frequency bands, thereby producing a plurality of pre-processed channels; channel energy estimation means for generating an estimate of the energy in each of said plurality of pre-processed channels; background noise estimation means for generating and storing estimates of the background noise energy based upon said channel energy estimates, and for periodically detecting the minima of a simulated post-processed signal energy level such that said background noise estimates are updated only during said minima, said simulated post-processed signal being obtained by multiplying said plurality of pre-processed channels by predetermined channel gain values; channel SNR estimation means for generating an estimate of the signal-to-noise ratio (SNR) of each individual channel based upon said channel energy estimates and said background noise estimates; channel gain controlling means for providing said channel gain values corresponding to said channel SNR estimates; channel gain modifying means for adjusting the gain of each of said plurality of pre-processed channels provided by said signal dividing means according to said channel gain values, thereby producing a plurality of post-processed channels; and channel combination means for recombining said plurality of post-processed channels to produce said post-processed output signal. - View Dependent Claims (28, 39)
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40. The method of attenuating the background noise from a noisy input signal to produce a noise-suppressed output signal in a noise suppression system comprising the steps of:
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separating the input signal into a plurality of pre-processed signals representative of selected frequency channels; modifying an operating parameter of each of said plurality of pre-processed signals to provide a plurality of post-processed signals; and generating a modification signal responsive to said plurality of pre-processed signals and said plurality of post-processed signals, whereby said modification signal enables the operating parameter of each of said plurality of pre-processed signals to be modified. - View Dependent Claims (43, 44)
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41. The method of attenuating the background noise from a noisy input signal to produce a noise-suppressed output signal in a noise suppression system comprising the steps of:
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separating the input signal into a plurality of pre-processed signals representative of selected frequency channels; modifying an operating parameter of each of said plurality of pre-processed signals to provide a plurality of post-processed signals; generating a control signal representative of said post-processed signals; and generating a modification signal responsive to said plurality of pre-processed signals and said control signal, whereby said modification signal enables the operating parameter of each of said plurality of pre-processed signals to be modified. - View Dependent Claims (42)
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45. The method of attenuating the background noise from a noisy input signal to produce a noise-suppressed output signal by spectral gain modification, comprising the steps of:
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separating the input signal into a plurality of pre-processed signals representative of selected frequency channels; modifying the gain of each of said plurality of pre-processed signals in response to estimates of the signal-to-noise ratio (SNR) in each individual channel to provide a plurality of post-processed signals; and generating said SNR estimates in each individual channel based upon the current signal energy estimate of the pre-processed signal in each individual channel and the previous noise energy estimate of the pre-processed signal in each individual channel as determined by the detected minima of said plurality of post-processed signals. - View Dependent Claims (47, 49, 50, 51)
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46. The method of attenuating the background noise from a noisy input signal to produce a noise-suppressed output signal by spectral gain modification, comprising the steps of:
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separating the input signal into a plurality of pre-processed signals representative of selected frequency channels; generating an estimate of the signal-to-noise ratio (SNR) in each individual channel based upon the current signal energy estimate of the pre-processed signal in each individual channel and the previous noise energy estimate of the pre-processed signal in each individual channel as determined by the detected minima of a simulated output signal energy level, said simulated output signal being obtained by multiplying said plurality of pre-processed signals by a predetermined gain value; producing said predetermined gain value in response to said SNR estimates; and the gain of each of said plurality of modifying the gain of each of said plurality of pre-processed signals in response to said predetermined gain value to provide a plurality of post-processed signals. - View Dependent Claims (48)
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Specification