Fricativization of Voiceless Aspirates in Bangla: a sound change in progress?

One of the ways of investigating the phonetic factors that lead to sound change is to investigate similar factors as a source of phonetic variation in a contemporary language. This papers reports on an acoustic study of voiceless aspirates in Bangla, which was conceived as part of a larger investigation into possible phonetic factors underlying the diachronic change of voiceless aspirates to fricatives in Ancient Greek. The Bangla evidence is directly relevant for an understanding of the phonetic factors that underlie fricativization, as Bangla exhibits a phonemic contrast between voiceless aspirated and plan stops, as in Ancient Greek. This paper reports on acoustic results from a production experiment involving Bangla speakers reading texts in two styles: in slow, careful speech and in fast, casual speech. The results offer strong evidence of the fricativization of voiceless aspirates in Bangla in the fast speech condition, although similar patterns of fricativization are not observed in careful speech. Furthermore, even in those forms where fricativization does not occur in either speaking style, the stop closure interval of the aspirate is proportionately shorter relative to the aspiration interval; i.e., there is a temporal reduction of the stop closure interval. As a secondary finding, we also observed that a sequence of plain stop + /h/ across a word boundary is realized differently in fast and careful speech; the fast speech forms are non-distinct from the single segment voiceless aspirate. Taken together, these results provide evidence of style-dependent variation of voiceless aspirates in Bangla. The further observation that the speakers in this study differ in the frequency and extent of fricativization suggests the possibility of a sound change in progress, perhaps towards an allophonic variation of voiceless aspirates that yields fricatives in intervocalic position. These findings provide interesting evidence of variation in the phonetic realization of Bangla voiceless aspirates, and thus contribute to the descriptive phonetics of this language. In addition, the findings, if confirmed with a larger number of subjects, have implications for the roots of sound change affecting voiceless aspirates, as occurred in Ancient Greek dialects.