Acoustic Differences Between English /t/ Glottalization and Phrasal Creak

In American English, the presence of creaky voice can derive from distinct linguistic processes, including phrasal creak (prolonged irregular voicing, often at edges of prosodic phrases) and coda /t/ glottalization (when the alveolar closure for syllablefinal /t/ is replaced by or produced simultaneously with glottal constriction). Previous work has shown that listeners can differentiate words in phrasal creak from those with /t/ glottalization, which suggests that there are acoustic differences between the creaky voice derived from phrasal creak and /t/ glottalization. In this study, we analyzed vowels preceding syllable-final /t/ in the Buckeye Corpus, which includes audio recordings of spontaneous speech from 40 speakers of American English. Tokens were coded for presence of phrasal creak (prolonged irregular voicing extending beyond the target syllable) and /t/ glottalization (whether the /t/ was produced only with glottal constriction). Eleven spectral measures of voice quality, including both harmonic and noise measures, were extracted automatically and discriminant analyses were performed. The results indicate that the discriminant functions can classify these sources of creaky voice above chance, and that Cepstral Peak Prominence, a measure of harmonics-to-noise ratio, is important for distinguishing phrasal creak from glottalization.