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Parametric speech codec for representing synthetic speech in the presence of background noise

  • US 7,092,881 B1
  • Filed: 07/26/2000
  • Issued: 08/15/2006
  • Est. Priority Date: 07/26/1999
  • Status: Active Grant
First Claim
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1. A system for processing an audio signal comprising:

  • means for dividing the audio signal into segments, each segment representing a portion of the audio signal occurring in one of a succession of time intervals;

    means for detecting for each segment the presence of a fundamental frequency;

    means responsive to the detecting means for determining the voicing probability for each segment by computing a ratio between voiced and unvoiced components of the audio signal, the determining means comprising;

    means for windowing each segment of the audio signal;

    means for computing the spectrum of the windowed segment;

    means for computing correlation coefficients of each segment using at least the spectrum;

    means for estimating a voicing threshold for each segment, comprising;

    means for dividing the spectrum into a plurality of non-linear bands, wherein the low bands of the spectrum have a higher resolution than the high bands of the spectrum;

    means for evaluating at least one voice measurement for each of the plurality of bands; and

    means for determining the voicing threshold for each segment using the at least one voice measurement; and

    means for comparing the correlation coefficients with the voicing threshold for each segment;

    means for separating the signal in each segment into a voiced portion and an unvoiced portion on the basis of the voicing probability, wherein the voiced portion of the signal occupies the low end of the spectrum and the unvoiced portion of the signal occupies the high end of the spectrum for each segment; and

    means for separately encoding the voiced portion and the unvoiced portion of the audio signal.

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