Abstract: In the speech recognition system disclosed herein, an input utterance is submitted to both a large vocabulary isolated word speech recognition module and a small vocabulary continuous speech recognition module. The two recognition modules generate respective scores for identified large vocabulary models and for sequences of small vocabulary models. The score provided by the continuous speech recognizer is normalized on the basis of the length of the speech input utterance and an arbitration algorithm selects among the candidates identified by the recognition modules. Preferably, the competing scores from the two recognizers are scaled by a factor or factors empirically trained to minimize incursion by each of the vocabularies on correct results from the other vocabulary.

Abstract: Preliminary screening of vocabulary models is provided by successively applying two different high speed distance measuring functions which provide progressively increasing measurement accuracy. Both distance measuring functions utilize subsampled representations of the unknown speech segment and the vocabulary models. The initial screening function achieves very high speed by eliminating certain usual time warping constraints and by precalculating a table of distance values which can be used for all vocabulary models. The second screening function yields improved accuracy in spite of possible endpointing errors by comparing extra frames, preceding and following the presumed unknown word, with noise models appended to each vocabulary model.