Constraints on articulation rate: utterance length, age, and gender across North American and British Isles Englishes

This study examines how articulation rate is structured across a large and heterogeneous set of English varieties with respect to both speech production constraints and social factors. Through Bayesian distributional regression modelling of articulation rate mean and variance across 33 varieties of British and North American English drawn from 16 spontaneous speech corpora collected as part of the SPeech Across Dialects of English (SPADE) project, we observe that the within-speaker utterance length effect on articulation rate (whereby longer utterances are produced at a faster rate and with less between-utterance variance) is large and broadly consistent across varieties. Specifically, the effect on mean rate exhibits modest variability across varieties, and between-utterance variance shows high cross-variety consistency. Small but consistent effects of speaker gender and age on articulation rate are observed across all varieties in both size and direction, and neither effect can be attributed to differences in the length of utterances, indicating that the source of these social differences lies outside of any systematic variability in utterance length. These findings across 33 hetereogeneous varieties show that the constraints imposed by utterance length on articulation rate are largely invariant across the regional and stylistic diversity of naturally-occurring English speech, while social factors exert consistent, independent influences.