The relationship between fundamental frequency and within-speaker vowel reduction

Abstract

The contribution(s) of fundamental frequency (F0) to vowel production has potential theoretical and clinical implications. The sufficient contrast hypothesis [Diehl et al., J. Phon. 24, 187–208 (1996)] suggests that a high F0 is associated with effects of spectral undersampling, and thus may require more exaggerated formant frequencies to maintain the perceptual distinctiveness of vowels. Nonetheless, studies on the interplay between F0 and vowel acoustics would appear inconclusive [Byrd, J. Acoust. Soc. Am. 92, 593–596 (1992)] [Weirich & Simpson, J. Acoust. Soc. Am. 134, 2965–2974 (2013)]. This study evaluated the sufficient contrast hypothesis as a within-speaker mechanism, with an overarching hypothesis that formant frequency exaggeration associated with spectral undersampling, if any, occurs within a given production system (i.e., speaker). To this end, formant frequencies of vowels and F0 were obtained for the same speaker across different speaking tasks. Within speaker, it was hypothesized that vowel formant frequencies as well as F0 change across tasks. More importantly, average F0 is hypothesized to be negatively correlated with the degree of vowel formant frequency reduction within-speaker across tasks. That is, a vowel system produced with a higher F0 would be less prone to reduction because the spectral peaks are better defined. The contribution(s) of fundamental frequency (F0) to vowel production has potential theoretical and clinical implications. The sufficient contrast hypothesis [Diehl et al., J. Phon. 24, 187–208 (1996)] suggests that a high F0 is associated with effects of spectral undersampling, and thus may require more exaggerated formant frequencies to maintain the perceptual distinctiveness of vowels. Nonetheless, studies on the interplay between F0 and vowel acoustics would appear inconclusive [Byrd, J. Acoust. Soc. Am. 92, 593–596 (1992)] [Weirich & Simpson, J. Acoust. Soc. Am. 134, 2965–2974 (2013)]. This study evaluated the sufficient contrast hypothesis as a within-speaker mechanism, with an overarching hypothesis that formant frequency exaggeration associated with spectral undersampling, if any, occurs within a given production system (i.e., speaker). To this end, formant frequencies of vowels and F0 were obtained for the same speaker across different speaking tasks. Within speaker, it was hypothesized that vowe...