Preservation of vocal tract length in speech. A negative finding

A primary determinant of vowel quality is vocal tract shape; one aspect of which is vocal tract length. It has been suggested [Perkell, Physiology of Speech Production (MIT, Cambridge, 1969); Riordan, J. Acoust. Soc. Am. 62, 998-1002 (1977)] that vocal tract length is controlled directly, and that one mechanism for its regulation is a coordination between labial and laryngeal gestures. Riordan (1977) observed compensatory changes in the vertical position of the larynx when the characteristic lip protrusion of a rounded vowel was impeded. Although subjects in this study accurately produced the vowels /i/, /a/, /u/, and /delta/ with different amounts of lip protrusion, no compensatory larynx height adjustments were observed.