Method and apparatus for generating models of spoken words based on a small number of utterances

A method of modeling words, said method comprising the steps of:

• measuring the value of at least one feature of a first utterance of a word during each of a series of successive time intervals to produce a first series of feature vector signals representing the feature values of the first utterance;
• measuring the value of at least one feature of a second utterance of the same word during each of a series of successive time intervals to produce a second series of feature vector signals representing the feature values of the second utterance;
• storing two or more probabilistic word model signals, each probabilistic word model signal representing a probabilistic model of the word;
• calculating, for each probabilistic word model and for each utterance, a match score representing the closeness of a match between the probabilistic word model and the series of feature vector signals produced by the utterance;
• calculating, for each probabilistic word model, an average-model match score representing the average match score for the word model and all utterances;
• selecting a first probabilistic word model having the best average-model match score;
• selecting a second probabilistic word model;
• identifying, for each utterance, a best-of-set match score representing the best match score between the utterance and the first and second probabilistic word models;
• calculating a set-average match score representing the average best-of-set match score for the first and second probabilistic word models and all utterances;
• and
• modeling the word with both the first and second probabilistic word models if the set-average match score surpasses the best average-model match score by a nonzero threshold value.

An apparatus for modeling words, said apparatus comprising:

• means for measuring the value of at least one acoustic feature of each of at least two utterances of a word;
• means for storing a selection set of one or more probabilistic word model signals, each probabilistic word model signal in the selection set representing a probabilistic model of the word;
• means for calculating, for the selection set, a match score representing the closeness of a match between the probabilistic word models in the selection set and the value of the acoustic feature of each utterance;
• means for storing a candidate set of one or more probabilistic word model signals, each probabilistic word model signal in the candidate set representing a probabilistic model of the word, each probabilistic word model in the candidate set being different from each probabilistic word model in the selection set;
• means for storing an expansion set comprising the probabilistic word model signals in the selection set and one probabilistic word model signal from the candidate set;
• means for calculating, for the expansion set, a match score representing the closeness of a match between the probabilistic word models in the expansion set and the value of the acoustic feature of each utterance;
• and
• means for modeling the word with the word models in the expansion set if the expansion set match score surpasses the selection set match score by a nonzero threshold value.