Abstract:
To analyze and compare the acoustic characteristics of the formant frequencies and durations of the Bangkok Thai monophthonds in the unstressed syllables of 2-syllable [sw] and 3-syllable [sw1w2] rhythmic units. The data was collected from ten native female speakers. All informants were asked to tell a few stories in order to obtain connected speech. The utterances were analyzed auditorily to search for 2-syllable and 3-syllable rhythmic units and then the nine short vowels and the nine long vowels occurring in the unstressed syllables were selected for measurement. The formant frequency and duration of the vowels was analyzed by using Pratt, version 4.2.31. It was found that the formant frequency values of the first and the second formants of the Thai mid central vowel are similar to those of the first and second formants of the centralized vowel. However, only the first formants of the mid front ; mid central ; mid back and low back, and only the second formants of the high central and low central are similar to those of the first and second formant of the centralized vowel respectively. It cannot be said exactly that the first and the second formants of the short and long vowels in the pairs w-w1 and w-w2 are higher or lower than each other. Both the first and the second formants of the shorts and long vowels in the pair w1-w2 are slightly different. In w1 and w2, the duration of the short and long vowels is shorter than that of the short and long vowels in w. The duration of the short and long vowels in the pair w1-w2 is a little different. In most vowels, the differences in the first and the second formants and in the duration of the short and long vowels is not statistically significant (p<0.05). However, in the three types of unstressed syllables (w, w1, w2), there are significant differences between the average duration of the short vowels and the long vowels. The results of the acoustical measurement indicate that in the unstressed syllables of all types, the length distinction is still preserved. Moreover, in the unstressed syllables, It has been found that short Thai vowels tend to be more centralized than long vowels. This indicates that long vowels are more robust than short ones. In conclusion, the formant frequency values and the duration values of the short and long vowels in w, w1, w2 are slightly different but this is largely insignificant. It seems that the structures of rhythmic units have less influence on both the formant frequency and duration of vowels on all types of unstressed syllables than expected.