The boundary-induced modulation of obstruents and tones in Thai

Limited studies have suggested that tones can be strengthened in domain-initial positions, suggesting that domain-initial strengthening (DIS) effects in a tone language extend beyond the first segment of a prosodic domain. However, these studies have yielded unclear results. This study investigated whether DIS causes boundary-induced changes in tones. This study analyzed the maximum fundamental frequency (f₀) of the falling, mid, and low tones in Thai along with acoustic measures of consonants, including the Voice Onset Times (VOTs) of /b/, /p/, and /pʰ/, frication duration of /f/, and consonant-induced f₀ perturbation effects associated with these four consonants in domain-initial and domain-medial positions. Some evidence of DIS effects on tones was found, suggesting that DIS effects in a tone language can extend to tone production realized with the vowel that is beyond the first segment. Additionally, the VOTs of /b/, /p/, and /pʰ/ were more negative, unchanged, and longer, respectively, the frication of /f/ was longer, and f₀ following /pʰ/ was raised in a domain-initial position compared to a domain-medial position. The findings contribute to the current understanding of the prosody-phonetics interface, particularly with respect to the relationship between DIS and the realization of tones.