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Multiple variable threshold speech detector

  • US 4,277,645 A
  • Filed: 01/25/1980
  • Issued: 07/07/1981
  • Est. Priority Date: 01/25/1980
  • Status: Expired due to Term
First Claim
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1. Apparatus for indicating the occurrence of speech in a signal indicative of both speech and noise, the apparatus including:

  • means for generating (13) a representation of the average magnitude of the signal during a moving time interval;

    the apparatus being characterized by classifying means (19) for receiving said representation and a noise level estimate, said classifying means generating a first output to indicate when said representation has prescribed attributes indicative of speech and a second output to indicate when said representation has prescribed attributes indicative of noise;

    level estimator means (21) responsive to said first and second outputs and said representation, said level estimator means providing a noise level estimate using the portion of said representation identified by the occurrence of said second output, said level estimator means providing a first decision level output by combining said noise level estimate and the portion of said representation defined by the occurrence of said first output in excess of a prescribed amount of said first decision level output; and

    comparing means (16) for providing an output indicative of the occurrence of speech signal activity when said first decision level is exceeded by the signal.

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