Prosodic realizations of global and local structure and rhetorical relations in read aloud news reports

The aim of this research is to study effects of global and local structure of texts and of rhetorical relations between sentences on the prosodic realization of sentences in read aloud text. Twenty texts were analyzed using Rhetorical Structure Theory. Based on these analyses, the global structure in terms of hierarchical level, the local structure in terms of the relative importance of text segments and the rhetorical relations between text segments were identified. The texts were read aloud. Pause durations preceding segments, F0-maxima and articulation rates of the segments were measured. It was found that speakers give prosodic indications about hierarchical level by means of variations in pause duration and pitch range: the higher the segments are connected in the text structure, the longer the preceding pauses and the higher the F0-maxima are realized. Also, it was found that speakers articulate important segments more slowly than unimportant segments, and that they read aloud causally related segments with shorter in-between pauses and at faster rate than non-causally related segments. We conclude that variation in pause duration and F0-maximum is a robust means for speakers to express the global structure of texts, although this does not apply to all speakers. Speakers also vary pause duration and articulation rate to indicate importance of sentences and meaning relations between sentences.