Noise reduction system
First Claim
1. A system for reducing noise in a wideband signal having at least one narrow frequency component comprising:
- a filterbank comprising a first filter having a first frequency and a first output and a second filter having a second frequency and a second output, wherein the phases of said first frequency and said second frequency differ by 180 degrees about a third frequency;
a running cross-correlator interconnected to said first filterbank for comparing said first output of said first filter and said second output of said second filter; and
an analysis-synthesis filterbank for attenuating said wideband signal at said third frequency in response to said running cross-correlator.
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Accused Products
Abstract
A system for reducing noise in a wideband signal, such as speech, using a first filterbank and running cross-correlator to detect narrowband frequency components in the signal and an analysis-synthesis filterbank to attenuate the wideband signal in which narrowband frequency components are not detected. The narrowband frequency components are detected by performing a running cross-correlation of the outputs of two bandpass filters that have center frequencies that straddle the narrowband frequency and differ by 180 degrees relative to each other at the frequency to be detected. Relatively low value cross-correlations indicate that a signal is present in a given frequency band and high value cross-correlations indicate only noise is present. The wideband signal is processed by an analysis-synthesis filterbank to attenuate bands where narrowband frequency components have not been detected and to pass or amplify bands where narrowband frequency components have been detected.
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Citations
11 Claims
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1. A system for reducing noise in a wideband signal having at least one narrow frequency component comprising:
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a filterbank comprising a first filter having a first frequency and a first output and a second filter having a second frequency and a second output, wherein the phases of said first frequency and said second frequency differ by 180 degrees about a third frequency;
a running cross-correlator interconnected to said first filterbank for comparing said first output of said first filter and said second output of said second filter; and
an analysis-synthesis filterbank for attenuating said wideband signal at said third frequency in response to said running cross-correlator. - View Dependent Claims (2, 3, 4, 5)
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6. A method for reducing noise in a wideband signal, comprising the steps of:
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(a) filtering said wideband noise at a first frequency to produce a first filter output;
(b) filtering said wideband noise at a second frequency to produce a second filter output, wherein the phases of said first frequency and said second frequency differ by 180 degrees about an intermediate third frequency;
(c) performing a running cross-correlation of said first filter output and said second filter output; and
(d) attenuating said wideband signal at said third frequency according to said running cross-correlation. - View Dependent Claims (7, 8, 9, 10, 11)
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Specification