The Glottal Fricative and Schwa Deletion in Hindi : Implications for Speech Synthesis

Abstract

Hindi is known to have a general process of schwa deletion, whereby unstressed schwas in open syllables are dropped when preceded by stressed syllables, as in /ʧa:həte:/ >[ʧa:hte:] ‘like- OBL’, /kəhəna:/ >[keɦna:] ‘say- INF’, but not in /ʃəhər/ [ˈʃəhər] ‘city’ (closed syllable), and /bəhəttər/ > [bəˈhəttər] ‘seventy-two’ (stressed). It has been found by the present authors that although the schwa following a /h/ may be ‘heard’ to be deleted, in speech synthesis based on trained data, the deletion of the schwa leads to problems. Along with the schwa, /h/ too gets dropped. The acoustic features of /h/ in relation to the presence of flanking vowels and a following consonant after the deletion of the following schwa need examining. In the present study a total number of 22 words including content words (nouns, verbs, adjectives) and grammatical words (pronouns, auxiliary verbs) were recorded in the speech of 8 speakers- four female and 4 male. Thus, the total number of tokens analyzed for the data were 22x8 =176. An attempt is made in the paper to account for the merger of /h/ with schwa in intervocalic unstressed contexts. It is shown that speech synthesis programmes must treat these contexts of schwa deletion as exceptions.