Fluent speech prosody: Framework and modeling

The prosody of fluent connected speech is much more complicated than concatenating individual sentence intonations into strings. We analyzed speech corpora of read Mandarin Chinese discourses from a top-down perspective on perceived units and boundaries, and consistently identified speech paragraphs of multiple phrases that reflected discourse rather than sentence effects in fluent speech. Subsequent cross-speaker and cross-speaking-rate acoustic analyses of identified speech paragraphs revealed systematic cross-phrase prosodic patterns in every acoustic parameter, namely, F0 contours, duration adjustment, intensity patterns, and in addition, boundary breaks. We therefore argue for a higher prosodic node that governs, constrains, and groups phrases to derive speech paragraphs. A hierarchical multi-phrase framework is constructed to account for the governing effect, with complimentary production and perceptual evidences. We show how cross-phrase F0 and syllable duration patterns templates are derived to account for the tune and rhythm characteristic to fluent speech prosody, and argue for a prosody framework that specifies phrasal intonations as subjacent sister constituent subject to higher terms. Output fluent speech prosody is thus cumulative results of contributions from every prosodic layer. To test our framework, we further construct a modular prosody model of multiple-phrase grouping with four corresponding acoustic modules and begin testing the model with speech synthesis. To conclude, we argue that any prosody framework of fluent speech should include prosodic contributions above individual sentences in production, with considerations of its perceptual effects to on-line processing; and development of unlimited TTS could benefit most appreciably by capturing and including cross-phrase relationships in prosody modeling.