Multiple template speech recognition system

A method of recognizing an unknown utterance as one of a set of reference words comprising the steps of generating a set of feature signals representative of each of a plurality of utterances of each reference word;

• generating at least one template signal for each reference word responsive to the feature signal sets of said reference word, each template signal being representative of a group of said reference word feature signal sets;
• responsive to the unknown utterance, generating a set of signals representative of the features of said unknown utterance;
• jointly responsive to said unknown utterance feature signal set and each reference word template signal, forming a set of signals each representative of the similarity between said unknown utterance feature signal set and said template signal;
• characterized in that a plurality of similarity signals for each reference word is selected;
• a signal corresponding to the average of each reference word selected similarity signals is formed;
• and responsive to the average signals for all reference words, the unknown utterance is identified as the most similar reference word.

A speech recognition circuit for identifying an unknown utterance as one of a set of reference words comprising means responsive to each of a plurality of utterances of a reference word for generating a first signal representative of the prediction parameters of said utterance;

• means responsive to the first signals of each reference word for generating at least one template signal for said reference word, each template signal being representative of a group of the reference word first signals;
• means responsive to the unknown utterance for generating a second signal representative of the prediction parameters of said unknown utterance;
• means jointly responsive to the template signals of each reference word and the second signal for forming a set of signals each representative of the distance between said second signal and said reference word template signal;
• and means responsive to said reference word distance signals for identifying said unknown utterance as the reference word having the minimum distance signals characterized in that said template signal generating means (112) further comprises means (222, 224) responsive to the first signals of each reference word for generating and storing a set of signals each representative of the distance between a pair of said reference word first signals;
• means (222, 225, 226, 228, 230) responsive to said stored distance signals for successively partitioning the first signals of each reference word into clusters, the first signals of each cluster having a predetermined degree of similarity;
• and means (216, 230, 600) responsive to said distance signals for determining the centermost first signal of each cluster and for identifying said centermost first signal as the cluster template signal.

A method for identifying an unknown utterance as one of a set of reference words comprising the steps of generating a first signal representative of the prediction parameters of each of a plurality of utterances of a reference word;

• generating at least one template signal for each reference word responsive to the reference word first signals, each template signal being representative of a group of the reference word first signals;
• generating a second signal representative of the prediction parameters of said unknown utterance;
• jointly responsive to the template signals of each reference word and the second signal, forming a set of signals each representative of the distance between said second signal and said reference word template signal;
• responsive to the distance signals of all reference words, identifying the unknown utterance as the reference word having the minimum distance signals characterized in that said template signal generation for each reference word includes generating and storing a set of signals each representative of the distance between a pair of reference word first signals responsive to the first signals of said reference word;
• and successively partitioning the first signals of said reference word into clusters responsive to the stored reference word distance signals, the first signals of each cluster having a predetermined degree of similarity;
• determining the centermost first signal of each cluster responsive to said stored reference word distance signals;
• and identifying said centermost first signal as the cluster template signal.

A speech recognition circuit for identifying an unknown utterance as one of a set of reference words comprising:

• means responsive to each of a plurality of utterances of a reference word for generating a first signal representative of the prediction parameters of said utterance;
• means responsive to the first signals of each reference word for generating at least one template signal for each reference word, each template signal being representative of a group of reference word first signals;
• means responsive to the unknown utterance for generating a second signal representative of the prediction parameters of said unknown utterance;
• means jointly responsive to the template signals of each reference word and the second signal for forming a set of a signals each representative of the distance between the second signal and said reference word template signal;
• and means responsive to said reference word distance signals for identifying said unknown utterance as the reference word having the minimum distance signals;
• characterized in that said distance representative signal forming means (1803, 1806, 1810, 1815, 1817, 1820) further comprises means (205) responsive to said unknown utterance for determining the number of frames to the endpoint frame of the unknown utterance;
• means (880, 1806) for generating a third signal corresponding to the average frame distance between said second signal and said template prediction parameter signals until said endpoint frame of said unknown utterance, for determining the intermediate frame of the unknown utterance at which the speech signal energy of the unknown utterance from said intermediate frame to said endpoint frame is a predetermined portion of the total speech signal energy of the unknown utterance, and for generating a fourth signal corresponding to the average frame distance between said second signal and said template prediction parameter signals until said intermediate frame;
• and means (1817, 1820) for selecting the minimum of said third and fourth signals as said distance representative signal.

A method for identifying an unknown utterance as one of a set of reference words comprising the steps of generating a first signal representative of the prediction parameters of each of a plurality of utterances of each reference word;

• generating at least one template signal for each reference word responsive to the reference word first signals, each template signal being representative of a group of the reference word first signals;
• generating a second signal representative of the prediction parameters of said unknown utterance;
• jointly responsive to the template signals of each reference word and the second signal, forming a set of signals each representative of the distance between said second signal and said reference word template signal;
• responsive to the distance signals of all reference words, identifying the unknown utterance as the reference word having the minimum distance signals characterized in that the step of forming a set of signals each representative of the distance between said second signal and said reference template signal comprises the steps of determining the endpoint frame of the unknown utterance;
• generating a third signal corresponding to the average frame distance between said second signal and said template prediction parameter signals until said endpoint frame;
• determining the intermediate frame of said unknown utterance at which the unknown utterance speech signal energy from said intermediate frame to said endpoint frame is a predetermined portion of the total speech signal energy of said unknown utterance;
• generating a fourth signal corresponding to the average frame distance between the second signal and the template prediction parameter signals until said intermediate frame;
• and selecting the minimum of said third and fourth signals as said distance representative signal.