Voice onset time in Thai alaryngeal speech.

The perception and production of voicing contrast was investigated in utterances spoken by Thai alaryngeal speakers. Thai exhibits a three-category voicing distinction for bilabial /b, p, ph/ and alveolar /d, t, th/ stops and a two-category distinction for velar [k, kh] stops. Voice onset time (VOT) was measured in word-initial stops of words produced in isolation by 2 Thai esophageal speakers and 1 Thai user of an electronic artificial larynx. These measurements were compared with published VOT values for the same words spoken by 5 normal Thai speakers. Both esophageal speakers were capable of signaling voicing distinctions for /b, d/ and /p, t, k/. The electrolaryngeal speaker was able to signal /p, t, k/ only. Thai alaryngeal speakers were generally unsuccessful in signaling /ph, th, kh/. A cross-linguistic comparison to VOT in English suggests that no more than two voicing categories can be distinguished in these two forms of alaryngeal speech. Findings are interpreted to illustrate that the realization of stop voicing contrasts in alaryngeal speech depends on the number of voicing categories in a language, the relative positions of the voicing categories on the VOT continuum, and the form of alaryngeal speech.