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Method of using a dominant angle of incidence to reduce acoustic noise in a speech signal

  • US 5,539,859 A
  • Filed: 02/16/1993
  • Issued: 07/23/1996
  • Est. Priority Date: 02/18/1992
  • Status: Expired due to Term
First Claim
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1. Method of reducing acoustic noise in a received sound signal incorporating a speech signal by subtracting spectral components of noise from said received sound signal to reconstitute a speech signal spectrum, said method comprising the steps of:

  • applying Fourier transform processing to digital signals obtained by analog-to-digital conversion of signals supplied by two microphones spaced by a fixed distance and receiving said sound signal to produce two series of discrete data each discrete datum of which being associated with a respective frequency band of the spectrum of said sound signal and representing the energy magnitude and phase of said respective frequency band, said each of said two series being representative of both noise and speech components of said received sound signal spectrum, each individual difference in phase between the data of the two series associated with the same frequency band representing a respective individual angle of incidence of a respective portion of the received sound signal;

    determining a single dominant angle of incidence of said received sound signal from a plurality of the individual angles of incidence, said dominant angle of incidence representing an assumed angle of incidence of said speech signal;

    combining said two series to thereby obtain a single instantaneous spectrum of said received sound signal;

    for each frequency band of said instantaneous spectrum, comparing a respective tolerance threshold value with a respective absolute value of a respective difference between said dominant angle of incidence and said respective angle of incidence,forming a noise spectrum comprising the same frequency bands as the frequency bands of the instantaneous spectrum,updating the noise spectrum with the energy magnitude data associated with those frequency bands of the instantaneous spectrum for which the respective absolute value is greater than said respective tolerance threshold value to thereby form an updated noise spectrum; and

    subtracting said updated noise spectrum from said instantaneous spectrum to obtain an output spectrum approximating said speech signal spectrum.

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