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Apparatus for calculating a posterior probability of phoneme symbol, and speech recognition apparatus

  • US 6,041,299 A
  • Filed: 03/11/1998
  • Issued: 03/21/2000
  • Est. Priority Date: 03/11/1997
  • Status: Expired due to Fees
First Claim
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1. An apparatus for calculating a posteriori probabilities of phoneme symbols, comprising:

  • feature extracting means for extracting speech feature parameters from a speech signal of an uttered speech sentence composed of an inputted character series; and

    calculating means for calculating a a posteriori probability of a phoneme symbol of the speech signal, by using a bidirectional recurrent neural network,wherein said bidirectional recurrent neural network comprises;

    an input layer for receiving, as input signals, the speech feature parameters extracted by the feature extracting means and a plurality of hypothetical phoneme symbol series signals;

    an intermediate layer of at least one layer having a plurality of units; and

    an output layer for outputting a a posteriori probability of each phoneme symbol,wherein said input layer comprises;

    a first input neuron group having a plurality of units, for receiving, as input signals, a plurality of speech feature parameters and a plurality of phoneme symbol series signals;

    a forward module; and

    a backward module,wherein said forward module has a forward-in-time feedback connection, and generates and outputs to said intermediate layer, a plurality of parameters of a timing delayed by a predetermined unit time from a plurality of parameters outputted from said first input neuron group, based on a plurality of speech feature parameters and a plurality of phoneme symbol series signals, and wherein said backward module has a backward-in-time feedback connection, and generates and outputs to said intermediate layer, a plurality of parameters of a timing inversely delayed by a predetermined unit timing from a plurality of parameters outputted from said first input neuron group, based on a plurality of speech feature parameters.

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