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Method of distinguishing voice from noise

  • US 4,920,568 A
  • Filed: 10/11/1988
  • Issued: 04/24/1990
  • Est. Priority Date: 07/16/1985
  • Status: Expired due to Term
First Claim
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1. A method of distinguishing voice from noise in a sound signal comprising the steps ofsampling a sound signal periodically at a fixed frequency over a sampling period to obtain sampled values,dividing said sampling period equally into a plural N-number of intervals,identifying each of said intervals as a vowel interval, a noise interval or a no-sound interval by a predefined identification procedure,obtaining an N1 -number which is the total number of said intervals identified as a vowel interval, and an N2 -number which is the total number of said intervals identified as a noise interval, andconcluding that said sampling period is a voice period if (N1 +N2)/N is greater than a predetermined first critical number r1 and N1 /(N1 +N2) is greater than a predetermined second critical number r2,said predefined procedure for each of said intervals including the steps ofcalculating a power value from the absolute squares of said sampled values,calculating a cepstrum sum from the absolute values of linear predictive (LPC) cepstrum coefficients obtained from said sampled values, andidentifying said interval to be a vowel interval if said power value is greater than an empirically predetermined first threshold value and said cepstrum sum is greater than an empirically predetermined second threshold value.

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