Diphthong formant transitions in four speaking tasks.

Abstract

Diphthongs have been demonstrated to have longer durations and to involve more extensive articulatory gestures, reflected as larger frequency changes, when compared to monophthongs [Lehiste, I., and Peterson, G. E., J. Acoust. Soc. Am. 33, 268–277 (1961); Holbrook, A. and Fairbanks, G., J. Speech Hear. Res. 5, 38–58 (1962)]. However, limited work has documented the nature of diphthong variability. This study describes and examines diphthong formant transitions in the speech production of ten healthy male native speakers of American English, with Wisconsin dialects, to identify and evaluate the pattern, if any, of diphthong variability in four speaking tasks: conversational speech, story reading, sentence in citation form, sentence in clear speech. The study is motivated by the phenomenon of vowel reduction [Lindblom, J. Acoust. Soc. Am. 35, 1773–1781 (1963)], which has been documented widely for monophthongs, as well as speaking rate-induced changes in diphthong formant transitions [Gay, T., J. Acoust. Soc. Am. 44, 1570–1573 (1968)]. Five diphthongs /eɪ/, /ɑɪ/, /ɑU/, /oU/, and /ɔɪ/ in American English are included, and formant transition measures, including transition duration, transition extent, and derived slope (i.e., transition extent/duration) are used for analysis. Findings are discussed within the framework of the acoustic theories of speech production.