Perception of stress in Thai

Abstract

This study assesses the relative contribution of four parameters—duration, amplitude, fundamental frequency and vowel quality—to the perception of stress in Thai. Previous acoustic studies [e.g., S. Potisuk et al., Phonetica 53, 200–220 (1996)] have identified these four parameters as varying with stress, but perceptual tests in which these parameters are independently controlled have been needed. For this experiment, stimuli were created by digitally manipulating the four parameters in minimal pairs (compounds versus phrases) that differ only in stress pattern. Subjects were asked to choose between two contexts signaling whether the stimuli they heard contained a compound or a phrase token. Duration was found to be the strongest perceptual cue to stress. Sometimes, stress was signaled by the combination of duration and vowel quality. Results also showed an effect of subjects bias to judge noun–verb tokens as phrases and noun–noun tokens as compounds. If the bias conflicted with decision signaled by duration and vowel quality, effects caused by amplitude variation were observed. Finally, fundamental frequency did not appear to play any role in signifying stress. The results thus support the following hierarchy of perceptual correlates to stress in Thai: duration, vowel quality/ bias, amplitude, and fundamental frequency.