An Approach to syntactic recognition without phonemics

Linguistic and perceptual arguments suggest that, in speech recognition systems, syntactic hypotheses should be formed before phonemic segments are identified. Prosodic features can provide some cues to constituent structure. In a variety of texts and excerpts from conversations, spoken by several talkers, a decrease in voice fundamental frequency (F0) usually occurred at the end of each major syntactic constituent, and an increase in F0occurred near the beginning of the following constituent. A computer program based on this regularity correctly detected over 80 percent of all syntactically predicted boundaries. Some boundaries between minor constituents were also detected by the fall-rise patterns in F0. False boundary detections resulted from F0variations at boundaries between vowels and consonants, but most such false alarms could be eliminated by setting a minimum percent variation in F0for a boundary detection. Sentence boundaries were accompanied by large F0increases and substantial pauses. The categories of constituents affect boundary detection results, with noun phrase-verbal sequences showing particularly infrequent detection. Prosodic cues to stress patterns and stress-to-syntax rules may be used to detect other aspects of syntactic structure. Syntactic structure hypotheses might then be used to guide phonetic recognition procedures within constituents.