Tonal Effects on Voice Onset Time

This study examines the influence of lexical tone on voice onset time (VOT) in Mandarin and Hakka spoken in Taiwan. The examination of VOT values for Mandarin and Hakka word-initial stops /p, t, k, p, t, k/ followed by three vowels /i, u, a/ in different lexical tones revealed that lexical tone has significant influence on the VOT values for stops. The results are important as they suggest that future studies should take the influence of lexical tone into account when studying VOT values and when designing wordlists for stops in tonal languages. In Mandarin, stops’ VOT values, from the longest to the shortest, are in MR, FR, HL, and HF tones. This sequence is the same as in Liu, Ng, Wan, Wang, and Zhang (2008). Later, however, it was found that it is very likely that the sequence results from the existence of non-words. In order to produce non-words correctly, participants tended to pronounce them at a slower speed, especially those in MR tone. Therefore, we further examined the data without non-words, in which no clear sequence was found. For Hakka, post-hoc tests (Scheffe) show that aspirated stops in entering tones, which are syllables ending with a stop, have significantly shorter VOT values than they have in other tones. Although the tonal effects on VOT values are not consistently found in different sets of data, probably due to a methodology problem, the possibility of tonal effect on VOT values could not be excluded. Tonal effect, thus, should be taken into consideration in designing word lists for VOT studies. Moreover, further studies should include both real words and non-words in separate sets of word lists to verify the current study results.