Interaction between duration, context, and speaking style in English stressed vowels

Acoustic observations are reported for English front vowels embedded in a /w—l/ frame and carrying constant main stress. The vowels were produced by five speakers in clear and citation-form styles at varying durations but at a constant speaking rate. The acoustic analyses revealed (i) that formant patterns were systematically displaced in the direction of the frequencies of the consonants of the adjacent pseudosymmetrical context; (ii) that those displacements depended in a lawful manner on vowel duration; (iii) that this context and duration dependence was more limited for clear than for citation-form speech, and that the smaller formant shifts of clear speech tended to be achieved by increases in the rate of formant frequency change. The findings are compatible with a revised, and biomechanically motivated, version of the vowel undershoot model Lindblom, J. Acoust. Soc. Am. 35, 1773–1781 (1963) that derives formant patterns from numerical information on three variables: The ‘‘locus-target’’ distance, vowel duration, and rate of formant frequency change. The results further indicate that the ‘‘clear’’ samples were not merely louder, but involved a systematic, undershoot-compensating reorganization of the acoustic patterns.