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Decision-directed frame-synchronous adaptive equalization filtering of a speech signal by implementing a hidden markov model

  • US 5,864,806 A
  • Filed: 05/05/1997
  • Issued: 01/26/1999
  • Est. Priority Date: 05/06/1996
  • Status: Expired due to Fees
First Claim
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1. A method of equalizing a speech signal constituted by an observed sequence of successive input sound frames, which speech signal is liable to be affected by disturbances, said method comprising a preliminary step of modelizing the speech signal by a hidden Markov model and, at each instant t, the further steps of:

  • (a) forming a plurality of equalization filters associated with paths in the Markov sense at instant t, on the basis of a plurality of earlier sound frames and on the basis of a plurality of parameters of the Markov model;

    (b) applying at least a plurality of said equalization filters to said frames to obtain, at instant t, a plurality of filtered sound frames sequences and an utterance probability for each of the paths respectively associated with the equalization filters applied;

    (c) selecting that one of said equalization filters which corresponds to a most probable path, in the Markov sense, which is that of said paths which has a highest utterance probability of the sequence of sound frames filtered by the corresponding applied equalization filter; and

    (d) selecting as an equalized frame the filtered frame supplied by the selected equalization filter.

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