This paper reports findings related to local changes in speech rate at the level of the phrase. It examines the tendency for local resets in speaking rate to align with boundaries delimiting groups of related words, and presents evidence for an overall slowing down of speaking rate throughout these phrase-sized chunks of speech. The durations of all segments in a phonetically-balanced two-hundred sentence database were normalised to facilitate comparison of the lengthening or shortening undergone by each, regardless of any differences in actual duration that may be attributable to differences in manner or place of articulation. The normalised data was fitted by a regression line having a positive slope that was steepest for shorter sentences. When longer sentences were divided into their component phrases, the slope of the regression lines increased. This indicates that segment durations tend to increase as a function of time within a phrase and are reset at phrase boundaries within the larger prosodic unit.
Bibliographic reference. Campbell, W. Nick (1991): "Phrase-level factors affecting timing in speech", In EUROSPEECH-1991, 629-632.