Tone Splits and Voicing Shifts in Thai: Phonetic Plausibility*

TLDR: This article showed that the pitch factors can influence phonemic judgments of voicing in a number of languages, such as Thai and Mandarin, leading to a claim that pitch factors are responsible for tone splitting.

Abstract: It has been shown for a number of languages that right after the release of a voiced stop consonant the fundamental frequency (FO) of the voice is likely to be lower than after the release of a voiceless stop and that such FO perturbations can influence phonemic judgments of voicing. This led to the designing of two experiments to test the phonetic plausibility of the argument: (1) CV syllables were synthesized with three values of voice onset time (VOT) acceptable as Thai Ib p phi. Each of these was combined with a continuum of FO contours that had previously been divided perceptually into the high, mid and low tones. These syllables were played to native speakers of Thai for tonal identification. (2) Labial stops with nine values of VOT separable into Ib p phi categories were coupled on synthetic mid-tone and low-tone CV syllables with upward and downward FO onsets varying in extent and duration. The resulting syllables were played for iden­ tification of the initial consonants. The historical argument receives modest support, especially from the second experiment, suggesting that during a period of tone splitting, under the influence of audible FO perturbations, speaken could have brought about the rephonemicization of the old consonant categories. Thus, these results give direct support to the argument that pitch factors led to voicing shifts but only indirect support to the claim that they gave rise to tone splits.