Voice onset time as a perceptual cue in voicing contrast in Tulu language

Voice onset time (VOT) is a perceptual cue in voicing contrast of stops in the word initial position. The current study aims to acoustically and perceptually characterize VOT in one of the major South Indian languages - Tulu. Stimuli consisted of 2 pairs of meaningful words with velar [/p/-/b/] and bilabial stops and [/k/-g/] in the initial position. These words were uttered by 8 normal native speakers of Tulu and recorded using Praat software. Both spectrogram and waveform views were used to identify the VOT. For perceptual experiment, 4 adult native speakers of Tulu were asked to identify the stimulus from where voicing was truncated in steps of 5 to 7 ms till lead VOT was 0 and silence was added after the burst in 5 msec steps till the lag VOT was 50 msec. The reaction time and the accuracy in identification were measured. Results of acoustic measurement showed no significant mean difference between lead VOTs of two voiced consonants. However, there was a significant difference between means of lag VOTs of voiceless consonants. Results of Perceptual measurement showed that as lead VOT reduces, probability of indentification of /g/ responses reduces; whereas changing VOT had little effect on reaction time and identification of /b/ responses. These results probably indicate that VOT is not necessary to perceive voiceles constants in Tulu but is necessary in the perception of voiced consonants. Thus VOT is a constant specific cue in Tulu.