Explaining the intrinsic pitch of vowels

Abstract

High vowels have a higher intrinsic pitch of voice than low vowels all other things being equal. In order to find the cause for these intrinsic pitch differences, two experiments were performed. The first was a study of the movement of the larynx using a photocell/computer tracking technique. The most common pattern found for larynx position during vowel production was /i/ most superior and relatively anterior, /a/ intermediate and posterior, and /u/ always lowest and generally most anterior, relative to /i/ and /a/. These results may possibly suggest that changes in vocal fold length contribute to intrinsic pitch differences between vowels. The low larynx position for the vowel /u/ apparently helps to enlarge the pharyngeal cavity to meet the acoustic requirements for this vowel. Larynx lowering with pharyngeal wall expansion should increase vocal fold tension and elevate pitch slightly. Inferior pharyngeal muscle constriction may account for the posterior position and low intrinsic pitch of the vowel /a/. A second experiment was designed to shed light on this possible mechanism. The effects of Arabic pharyngeal approximates on vowel pitch vis-a-vis the effects of Arabic stops were investigated, since pharyngeal constriction is a key feature for their production. Arabic pharyngeal approximates were found to cause a significantly lower pitch on following vowels than Arabic bilabial, alveolar, and velar stops. This is evidence that pharyngeal constriction and tongue retraction lower pitch. If pharyngeal constriction and tongue retraction vary inversely with vowel height, the same forces may act to automatically lower vowel pitch. Other hypotheses to account for intrinsic pitch differences between vowels are reviewed in the light of these pitch and larynx movement results and in the light of the Arabic pharyngeal effects observed. [This research is supported by the National Science Foundation.]