A study of vowel length in Thai

Abstract

In Thai, vowel length is contrastive (e.g., [cìp] ‘‘to sip’’–[ciìp] ‘‘to pleat’’). The main cue to distinguish short-long vowels in Thai is vowel duration [Abramson, 1962]. However, in some literature, there are other cues for vowel length in Thai, such as final nasal duration. This paper was aimed to see how important vowel duration and final nasal duration are as perceptual cues for Thai listeners. A perceptual experiment was conducted. Eighteen (near-) minimal pairs of Thai words were used, consisting of initial voiceless unaspirated stop [p], nine pairs of Thai vowels, a final voiceless velar stop [k] or an alveolar final nasal [n]. Short vowels were lengthened and long vowels were shortened at 10–30-ms steps, using LPC analysis and resynthesis. The same procedure was done for short and long final nasals at 10-ms steps. All 1148 tokens were put into a Thai frame sentence and randomized. Forty native Thai listeners listened to these tokens and judged whether each token had a short or a long vowel. The results are that vowel duration is the main perceptual cue to distinguish short and long vowels in Thai.