Patent Document ID: 4587670
Application ID: 06434516

Base Claim:
1. A speech analyzer for recognizing an utterance as one of a plurality of reference patterns each having a frame sequence of acoustic feature signals comprising: means for storing a set of K signals each representative of a prescribed acoustic feature of said plurality of reference patterns; means for storing a plurality of templates each representative of an identified spoken reference pattern, the template of each spoken reference pattern comprising signals representative of a first state, a last state and a preselected number N-2 intermediate states between said first and last states of a constrained hidden Markov model of said spoken reference pattern, N being independent of the number of acoustic feature frames in the acoustic feature frame sequence of the identified spoken reference pattern, a plurality of first type signals each representative of the likelihood of a prescribed acoustic feature signal of a reference pattern frame being in a predetermined one of said states, and a plurality of second type signals each representative of the likelihood of a transition from a prescribed acoustic feature signal in one of said states to another of said states of said template; means responsive to the utterance for forming a time frame sequence of acoustic feature signals representative of the speech pattern of the utterance; means responsive to said utterance feature signal sequence and said stored prescribed acoustic feature signals for selecting a sequence of said prescribed feature signals representative of the utterance speech pattern; means jointly responsive to said sequence of prescribed feature signals representative of the utterance and the reference pattern template N state constrained hidden Markov model signals for combining said utterance representative sequence of prescribed feature signal sequence with said reference pattern N state Markov model template signals to form a third type signal representative of the likelihood of the unknown utterance being the spoken reference pattern; and means responsive to the third type signals for the plurality of reference patterns for generating a signal to identify the utterance as one of the plurality of reference patterns.

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Claim 2:
2. A speech analyzer according to claim 1 wherein said third type signal generating means comprises: means for successively generating speech pattern frame processing interval signals for the sequence of prescribed acoustic feature signals; means operative in the current speech pattern frame processing interval responsive to the utterance representative prescribed feature signal of the current speech pattern frame and the reference pattern template N state constrained hidden Markov model signals for producing a set of signals representative of the likelihood of the utterance speech pattern being in a prescribed state of the Markov model template during said speech frame; and means operative in the speech pattern frame processing intervals responsive to the likelihood representative signal corresponding to the reference pattern Markov model template being in the last state during the last speech pattern frame for forming a signal representative of the probability of the speech pattern being obtained from the reference pattern N state Markov model template.