Spectral distribution of prosodic information

Prosodic speech cues for rhythm, stress, and intonation are related primarily to variations in intensity, duration, and fundamental frequency. Because these cues make use of temporal properties of the speech waveform they are likely to be represented broadly across the speech spectrum. In order to determine the relative importance of different frequency regions for the recognition of prosodic cues, identification of four prosodic features, syllable number, syllabic stress, sentence intonation, and phrase boundary location, was evaluated under six filter conditions spanning the range from 200-6100 Hz. Each filter condition had equal articulation index (AI) weights, AI = 0.10; p(C)_{isolated words} ≈ 0.40. Results obtained with normally hearing subjects showed that there was an interaction between filter condition and the identification of specific prosodic features. For example, information from high-frequency regions of speech was particularly useful in the identification of syllable number and stress, whereas information from low-frequency regions was helpful in identifying intonation patterns. In spite of these spectral differences, overall listeners performed remarkably well in identifying prosodic patterns, although individual differences were apparent. For some subjects, equivalent levels of performance across the six filter conditions were achieved. These results are discussed in relation to auditory and auditory-visual speech recognition.