Structure in talker-specific phonetic realization: Covariation of stop consonant VOT in American English

- Variation in phonetic realization across talkers is highly structured (patterned).
- Mean VOT values for word-initial stop consonants are correlated across talkers.
- Correlations are present in isolated speech and a large connected speech corpus.
- These patterns indicate a principle of uniformity that constrains phonetic systems.
- Patterned variation may underlie generalized perceptual adaptation to new talkers.

Variation across talkers in the acoustic-phonetic realization of speech sounds is a pervasive property of spoken language. The present study provides evidence that variation across talkers in the realization of American English stop consonants is highly structured. Positive voice onset time (VOT) was examined for all six word-initial stop categories in isolated productions of CVC syllables and in a multi-talker corpus of connected read speech. The mean VOT for each stop differed considerably across talkers, replicating previous findings, but importantly there were strong and statistically significant linear relations among the means (e.g., the mean VOTs of [pʰ] and [kʰ] were highly correlated across talkers, r>0.80). The pattern of VOT covariation was not reducible to differences in speaking rate or other factors known to affect the realization of stop consonants. These findings support a uniformity constraint on the talker-specific realization of a phonetic property, such as glottal spreading, that is shared by multiple speech sounds. Because uniformity implies mutual predictability, the findings also shed light on listeners׳ ability to generalize knowledge of a novel talker from one stop consonant to another. More broadly, structured variation of the kind investigated here indicates a relatively low-dimensional encoding of talker-specific phonetic realization in both speech production and speech perception.