Multilevel modeling of speaker variation in cross-dialectal articulation rate.

Abstract

Articulation rate (excluding pause time) in spontaneous speech was examined for northern speakers of American English from Wisconsin and for southern speakers from western North Carolina. The corpus consisted of speech samples from 192 speakers, males and females, ranging from 8 to 90 years old. The focus of this study is to model statistically both the between‐speaker and within‐speaker variations. Within‐speaker changes in tempo depend primarily on phrase length so that longer phrases, containing more syllables, tend to be spoken faster than shorter phrases. To capture this type of variation, mixed‐effect models were used and the phrase length was included as a predictor. Fixed‐effect covariates of interest included dialect, gender, age, and phrase length. The results indicate that phrase length has a highly significant fixed effect on articulation rate. When the differences in phrase length were controlled, the speech tempo of Wisconsin speakers was found to be significantly faster than of North Carolina speakers and male speech was significantly faster than female. The effects of age were also significant showing that articulation rate increases with age achieving the peak at 46 years and decreases with age thereafter. [Work supported by NIH.]