Quantifying rhythm: Interspeaker variation in %V

Abstract

The long-standing intuition that languages differ systematically in speech rhythm received support from an acoustic measure, %V (the ratio of vocalic material to the total duration of an utterance), which seemed to separate languages according to their perceived rhythms. Across studies, however, computations of %V values for target languages differ, raising the possibility that %V reflects not language-specific rhythmic habits, but the syllable structure of the particular utterances selected for analysis, and individual speaker differences. This paper replicates the %V methodology (using new recordings), and seeks to explain the high variability in %V by explicitly testing the link between %V, phonotactics, and individual speaker behavior. A high positive correlation is found between %V and an utterance's proportion of open syllables, while %V correlates negatively with the number of complex onsets in an utterance; these results support the hypothesis that utterance-level variation in syllable structure contributes substantially to the computed value of %V. However, the strength of this relationship varies across speakers. The goal of this paper is to determine the relative effects of utterance-level phonotactics, and individual speaker variation, on %V results, e.g., by comparing results when the same sentence is spoken by different speakers of a single language.