Demisyllable-based isolated word recognition system

A speaker-dependent speech recognition system is described for recognizing isolated word utterances using reference templates created by concatenating demisyllable (half-syllable) prototypes. Each word in a vocabulary is specified by one or more entries in a user-supplied lexicon containing a sequence of demisyllables drawn from a corpus of some 1000 units. Experiments were carried out with two talkers using a 1109-word "Basic English" vocabulary to assess the overall effectiveness of demisyllable representations for words. Also, the effects on performance of some simple modifications in demisyllable specifications and adjustments of demisyllable durations were investigated. The recognition error rates obtained for this vocabulary using demisyllable prototypes were 18-33 percent compared with 6-15 percent using whole word prototypes. Although the performance is substantially poorer using demisyllable representations in place of whole words, the approach of using a fixed inventory of smaller-than-word recognition units capable of representing any spoken word in a simple concatenative scheme is clearly an attractive alternative to whole-word prototypes for large-size vocabularies. The approach also has the potential of being effective in representing and recognizing continuous spoken utterances.