Relationship between discourse structure and dynamic speech rate

This paper regards one specific element of a larger research project on the acoustic determinants of information structure in spontaneous and read discourse in Dutch. From a previous experiment within that project it turned out that listeners used two main cues (viz. speaking rate and intonation) to differentiate between spontaneous and read speech. The aim of the present experiment is to investigate the role of one of these prosodic cues, i.e., the local variability in speaking rate, and to study the relationship between the information structure of a spoken discourse on the one hand, and dynamic speaking rate measurements of that discourse on the other hand. Results show that there is a large variability in average syllable duration over the various interpausal speech runs for each of the eight speakers. No straightforward relation is found between the number of syllables within a run and the average syllable duration. We hypothesize that, at least in spontaneous speech, variations in speaking rate are related to the (global and/or local) information structures in the discourse. Global analysis of the discourse structure in paragraphs and clauses reveals that for each of the speakers the average syllable duration of the first run of a paragraph is longer than the overall mean value per speaker in more than 60% of the cases. Inspection of the quartiles of runs with highest ASD-values and those with lowest ASD-values for each of the speakers shows quite different structures, which can be explained on the basis of partly local and partly global discourse characteristics.