The roles of vowel length and sentential context in onset pitch perturbations in Thai

Abstract

This study investigates the relationship between fundamental frequency at the onset of voicing (onset f0) and Voice Onset Time (VOT) in a tonal language with prevoiced, short-lag, and long-lag stops. Recent research on Thai and Vietnamese has suggested that higher f0 in the following vowel is conditioned by long-lag stops, but this effect occurs more in higher, not lower, tones and in words produced in isolation, not in a carrier phrase. An examination of previous studies, however, suggests that the effect may be moderated by vowel length and the type of carrier phrase. To determine whether this is true, this study compares onset f0 measured 40 ms after voicing onset in Thai low tone words with phonemically short and long vowels that occur in two types of carrier phrases and in isolation. The results show that prevoiced, not short- or long-lag, stops condition higher onset f0 in short, not long, vowels, and this effect takes place in words occurring in both types of carrier phrases, not in isolation. This suggests that vowel length may be a relevant factor. The results will be discussed further, and implications for onset f0 control will be offered.