Dawn M. Behne
Linguist. Inst., Univ. of Trondheim, N-7055 Dragvoll, Norway
Lynne C. Nygaard
Indiana Univ., Bloomington, IN 47405
Speaking rate, focal stress, and sentence position can affect the duration and spectral characteristics of vowels [e.g., B. Lindblom, J. Acoust. Soc. Am. 35, 1773--1781 (1963)]. However prior research has been less than conclusive in characterizing effects of these factors [cf. e.g., T. Gay, J. Acoust. Soc. Am. 63, 223--230 (1978)]. Previous findings [D. M. Behne and L. C. Nygaard, J. Acoust. Soc. Am. 90, 2254(A) (1991)] have confirmed the combined effects of these factors on vowel duration and have shown that vowels can be independently affected by speaking rate, focal stress, and sentence position. The goal of this paper is to characterize the effects of these factors on formant frequencies of vowels and relate them to effects on vowel duration. Using the vowels /(small capital eye), o, a, (ae ligature)/, conversations were developed with /kVt/ and /kVd/ as target words. In each conversation a target word occurred in initial and in final sentence position and was either focused or nonfocused by the discourse. Twelve subjects produced each conversation at three speaking rates. The present results demonstrated no effect of either speaking rate or focal stress on the spectral characteristics of the vowels, but relatively high first formant frequency and low second formant frequencies for vowels in final sentence position compared to initial sentence position. These findings verify that speaking rate, focal stress, and sentence position can concurrently influence syllable-internal timing with distinct acoustic effects. The results will be discussed in terms of vowel reduction and undershoot.