Abstract:
To study the duration, formant frequencies (F1 and F2), vowel space and variation within their space of short and long vowels in Hmong, Mien and Mal and to investigate the relationship between duration and formant frequency in order to prove the hypothesis that the acoustic characteristics of short vowels are different from those of long vowels. The informants were three speakers of each language. The three sets of data consist of minimal and analogous pairs with short and long vowels. Twelve vowels (6 phonemes): [i] [i:] (/i/) [e] [e:] (/e/) [ɨ] [ɨ:] (/ɨ/) [a] [a:] (/a/) [u] [u:] (/u/) [ɔ] [ɔ:] (/ɔ/), were used for Hmong which does not have phonological length. Fourteen vowels (13 phonemes): /i/ /i:/ /e/ /e:/ /ɛ/ /ɛ:/ /a/ /a:/ /u/ /u:/ [o] [o:] (/o/) /ɔ/ /ɔ:/, were used for Mien. Nine short and long counterparts (18 phonemes): /i/ /i:/ /e/ /e:/ /ɛ/ /ɛ:/ /ɨ/ /ɨ:/ /ǝ/ /ǝ:/ /a/ /a:/ /u/ /u:/ /o/ /o:/ /ɔ/ /ɔ:/, were used for Mal which has vowel length distinction. The duration and formant frequency of all vowels were analyzed with Praat version 4.5.06 and tested by t-Test (0.05 level of significance) using SPSS version 13.0 for Windows. The results indicate that the distinction between the average duration of short and long vowels is statistically significant and the ratio of duration for long-to-short vowels is 2:1, even though vowel length in Hmong is not phonologically significant like Mien (some vowels) and Mal (all vowels). In Mien (all vowels) and Mal (except central vowels), as well as duration, first formant is the cue to distinguish short and long vowels, while second formant can be used as the cue for back vowels only. The vowel space of short vowels is smaller than that of their long counterparts but the variation within the space of each short vowel is more dispersed than that of long vowels. A cross language comparison shows that the vowel space of Mal, which has a large inventory, is the smallest, while the vowel space of Hmong, which has a smaller inventory, is the largest. Moreover, the variation of each vowel in the vowel space does not depend on vowel inventory size.