Control of vocal-tract length in speech.
Essential for the correct production of vowels is the accurate control of vocal-tract length. Perkell [Psychology of Speech Production (MIT, Cambridge, MA, 1969)] has suggested that two important determinants of vocal-tract length are vertical larynx position and lip spreading/protrusion, often acting together. The present study was designed to determine whether constraining lip spreading/protrusion induces compensatory vertical larynx displacements, particularly on rounded vowels. Upper lip and larynx movement were monitored photoelectrically while French and Mandarin native speakers produced the vowels /i,y,u/ first under normal-speech conditions and then with lip activity constrained. Significant differences were found in upper-lip protrusion and larynx position depending on the vowel uttered. Moreover, the generally low-larynx position of rounded vowels became even lower  when lip protrusion was constrained. These results imply that compensatory articulations contribute to a contrast-preserving strategy in speech production.
D000162:Acoustics; D000328:Adult; D006801:Humans; D007830:Larynx / Q000502:physiology*; D008046:Lip / Q000502:physiology*; D008297:Male; D010700:Phonetics; D013060:Speech