Speech recognition system which creates acoustic models by concatenating

Abstract

A computerized speech recognition system creates acoustic models of phrases by concatenating acoustic models for individual words. The system stores an acoustic word model and spelling for each of its vocabulary words. When it receives the spelling of a multi-word phrase to be treated as a new vocabulary word, it stores that multi-word spelling as the spelling of the new vocabulary word, and a new acoustic model created by concatenating the acoustic word models of previous vocabulary words whose spellings correspond to words in the multi-word spelling as the acoustic model for the new word. The system can then perform speech recognition by comparing acoustic signals against the word models of stored vocabulary words, including those representing such multi-word phrases. Preferably when a multi-word model is formed, the individual acoustic models concatenated are modified to represent the coarticulation which takes place between words spoken continuously. This can be done by representing word models as sequences of individual phonemes, individual phonemes by phoneme-in-context models, and coarticulation by modifying the phoneme-in-context models of phonemes adjacent the boundary between concatenated words models to reflect the context of the phonemes on the other side of such word boundaries. The system can be a discrete word recognizer. The multi-word phrases can be selected by a user or be obtained from other programs running on the same computer as the speech recognizer, such as from one or more commands available in another program.