Adaptive LPC noise reduction system
First Claim
Patent Images
1. A noise suppression system comprising:
- a sampling circuit adapted to sample an audio input signal at a predetermined sampling rate;
a low-pass filter coupled with the sampling circuit and configured to pass low-frequency components of the sampled audio input signal;
a plurality of delay circuits configured to sequentially delay the low-frequency components of the sampled audio input signal to provide sequentially delayed signals;
an adaptive processor configured to process the sequentially delayed signals and update a plurality of linear predictive coefficient (LPC) values on a sample-by-sample basis, based on an error signal, where the error signal is based on a difference between an output of the low-pass filter and an output of the adaptive processor; and
a decision logic device coupled with the adaptive processor and configured to inhibit an update of the LPC values applied to a portion of the sampled audio input signal based on a determination that a wind buffet is not present in the portion of the sampled audio input signal;
a high-pass filter coupled with the sampling circuit and configured to pass high-frequency components of the sampled audio input signal; and
an adder configured to sum the error signal and an output of the high-pass filter to generate an output signal.
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Abstract
A noise suppression system reduces low-frequency noise in a speech signal using linear predictive coefficients in an adaptive filter. A digital filter may update or adapt a limited set of linear predictive coefficients on a sample-by-sample basis. The linear predictive coefficients may be used to provide an error signal based on a difference between the speech signal and a delayed speech signal. The error signal represents an enhanced speech signal having attenuated and normalized low-frequency noise components.
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Citations
19 Claims
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1. A noise suppression system comprising:
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a sampling circuit adapted to sample an audio input signal at a predetermined sampling rate; a low-pass filter coupled with the sampling circuit and configured to pass low-frequency components of the sampled audio input signal; a plurality of delay circuits configured to sequentially delay the low-frequency components of the sampled audio input signal to provide sequentially delayed signals; an adaptive processor configured to process the sequentially delayed signals and update a plurality of linear predictive coefficient (LPC) values on a sample-by-sample basis, based on an error signal, where the error signal is based on a difference between an output of the low-pass filter and an output of the adaptive processor; and a decision logic device coupled with the adaptive processor and configured to inhibit an update of the LPC values applied to a portion of the sampled audio input signal based on a determination that a wind buffet is not present in the portion of the sampled audio input signal; a high-pass filter coupled with the sampling circuit and configured to pass high-frequency components of the sampled audio input signal; and an adder configured to sum the error signal and an output of the high-pass filter to generate an output signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A noise suppression system comprising:
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a sampling circuit adapted to sample an input signal at a predetermined sampling rate; a low-pass filter coupled with the sampling circuit and configured to pass low-frequency components of the sampled input signal; an adaptive processor coupled with the low-pass filter and configured to update a plurality of linear predictive coefficient (LPC) values on a sample-by-sample basis, based on an error signal; where the error signal is based on a difference between an output of the low-pass filter and an output of the adaptive processor, and where the LPC values are configured to flatten the error signal across a frequency region of interest to provide the error signal as an enhanced speech signal having reduced low-frequency components; a wind buffet detector configured to detect whether wind buffets are present in the sampled input signal; a decision logic device coupled with the wind buffet detector and configured to inhibit adaptation of the LPC values in response to a determination by the wind buffet detector that a wind buffet is not present in the sampled input signal; a high-pass filter coupled with the sampling circuit and configured to pass high-frequency components of the sampled input signal; and an adder configured to sum the error signal and an output of the high-pass filter to generate an output signal. - View Dependent Claims (12, 13)
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14. A method for enhancing a signal provided to a user device, the method comprising:
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sampling an audio input signal at a predetermined sample rate; filtering the sampled audio input signal through a low-pass filter to pass low-frequency components of the sampled audio input signal; delaying the low-frequency components of the sampled audio input signal by multiple levels of delays to provide sequentially delayed signals; processing the sequentially delayed signals in an adaptive filter; adaptively updating linear predictive coefficient (LPC) values on a sample-by-sample basis based on an error signal, where the error signal is based on a difference between an output of the low-pass filter and an output of the adaptive filter; determining whether a portion of the sampled audio input signal includes wind buffets; inhibiting an update of the LPC values applied to the portion of the sampled audio input signal in response to a determination that the portion of the sampled audio input signal does not include a wind buffet; filtering the sampled audio input signal through a high-pass filter to pass high-frequency components of the sampled audio input signal; and adding the error signal and an output of the high-pass filter to generate an output signal. - View Dependent Claims (15, 16, 17, 18)
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19. A non-transitory computer-readable storage medium having processor executable instructions to provide a noise-reduced signal by performing the acts of:
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sampling an audio input signal at a predetermined sample rate; filtering the sampled audio input signal through a low-pass filter to pass low-frequency components of the sampled audio input signal; delaying the low-frequency components of the sampled audio input signal by multiple levels of delays to provide sequentially delayed signals; processing the sequentially delayed signals in an adaptive filter; adaptively updating linear predictive coefficient (LPC) values on a sample-by-sample basis based on an error signal, where the error signal is based on a difference between an output of the low-pass filter and an output of the adaptive filter; determining whether a portion of the sampled audio input signal includes wind buffets; inhibiting an update of the LPC values applied to the portion of the sampled audio input signal in response to a determination that the portion of the sampled audio input signal does not include a wind buffet; filtering the sampled audio input signal through a high-pass filter to pass high-frequency components of the sampled audio input signal; and adding the error signal and an output of the high-pass filter to generate an output signal.
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Specification