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Reduction of search space in speech recognition using phone boundaries and phone ranking

  • US 5,729,656 A
  • Filed: 11/30/1994
  • Issued: 03/17/1998
  • Est. Priority Date: 11/30/1994
  • Status: Expired due to Term
First Claim
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1. A method of recognizing speech, comprising the steps of:

  • a) inputting a plurality of words of training data;

    b) training a plurality of first binary decision trees to ask a maximally informative question at each node based upon contextual information in the training data, wherein each first binary decision tree corresponds to a different time in a sequence of the training data;

    c) traversing one of the first binary decision trees for every time frame of an input sequence of speech to determine a probability distribution for every time frame, the probability distribution being the probability that a node is a phone boundary;

    d) comparing the probabilities associated with the time frames with a threshold for identifying some time frames as boundaries between phones;

    e) providing an acoustic score for all phones between every given pair of boundaries to generate a second binary decision tree of such acoustic scores;

    f) traversing the second binary decision tree of such acoustic scores for all phones to rank the phones from best to worst on the basis of this score; and

    g) outputting a recognition result in response to the score.

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