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.

Abstract: In the speech recognizer disclosed herein, alignment of an unknown speech sediment, represented by a finely gradiated sequence of frames, with a model sediment represented by a sequence of states is performed by first preparing respective coarse sequences representing the unknown and model segments thereby to define a coarse matrix representing possible alignments. The fine sequences correspondingly define a fine matrix. A best alignment of the coarse sequences is determined thereby to define a coarse path through the coarse matrix. The coarse path is overlaid on the fine matrix and a corridor is defined which includes fine matrix locations which lie within a preselected metric of the coarse path. Only transitions within the corridor are calculated in determining the fine alignment of the unknown speech segment with the model segment, thereby significantly reducing the number of computations required.

Abstract: A speech recognition method and apparatus take into account a system transfer function between the speaker and the recognition apparatus. The method and apparatus update a signal representing the transfer function on a periodic basis during actual speech recognition. The transfer function representing signal is updated about every fifty words as determined by the speech recognition apparatus. The method and apparatus generate an initial transfer function representing signal and generate from the speech input, successive input frames which are employed for modifying the value of the current transfer function signal so as to eliminate error and distortion. The error and distortion occur, for example, as a speaker changes the direction of his profile relative to a microphone, as the speaker's voice changes or as other effects occur that alter the spectra of the input speech frames. The method is automatic and does not require the knowledge of the input words or text.