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Speech recognition method and system using triphones, diphones, and phonemes

  • US 5,502,790 A
  • Filed: 12/21/1992
  • Issued: 03/26/1996
  • Est. Priority Date: 12/24/1991
  • Status: Expired due to Term
First Claim
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1. A speech recognition method for recognizing a target vocabulary of words, phrases, or sentences, comprising the steps of:

  • (a) selecting a training vocabulary;

    (b) listing in a table (8) all triphones, diphones, and phonemes occurring in said training vocabulary;

    (c) obtaining spoken samples of said training vocabulary;

    (d) reducing said spoken samples to training data comprising sequences of labels;

    (e) identifying, in said training data, segments corresponding to the triphones, diphones, and phonemes in said table (8);

    (f) using the labels obtained in step (d) and segments identified in step (e) to construct a triphone HMM for each triphone in said table (8), and diphone HMM for each diphone in said table (8), and a phoneme HMM for each phoneme in said table (8);

    (g) storing each triphone HMM, diphone HMM, and phoneme HMM constructed in step (f) in a first dictionary (9) consisting of the HMMs thus stored;

    (h) creating HMMs for the target vocabulary by concatenating HMMs from said first dictionary (9), using triphones HMMs if available in said first dictionary (9), using diphone HMMs when triphone HMMs are not available, and using phoneme HMMs when neither triphone nor diphone HMMs are available.(i) storing the HMMs created in step (h) in a second dictionary (10); and

    (j) recognizing an utterance by reducing the utterance to a sequence of labels, computing probabilities of producing said sequence of labels from each HMM in said second dictionary (10), and selecting an HMM giving maximum probability.

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