Articulatory modeling of human and non-human vocal production

Abstract

This paper reviews two of the many questions that might be addressed by adapting articulatory models of vocal production across primate species. The first concerns vocal-fold shaping at phonation. The human folds have been modeled to have uniform cross-sectional shapes with round edges along the longitudinal axis, whereas MRI slices reveal an obvious vertical prominence of the mucosa near each vocal process. This shape, due to depressed vocal processes in adduction, somewhat resembles the pointed edges of the vocal membranes in nonhuman primates, which are incorporated in some models of chaotic phonation in those species. This suggests a model of vocal-fold vibration propagating back to the posterior glottis, or coupled oscillation for irregularities in human voices. The second concerns tongue-lip coordination. In human vowel inventories, tongue retraction typically accompanies rounding. In a case report, a trained Chimpanzee was able to produce back vowels /a, o, u/ in whispering, but could not coordinate these articulatory positions with voiced phonation. This suggests an innate neural circuit for patterned tongue-lip coordination as seen in sucking, and such a basic neural unit may be active in humans to simplify the articulatory control of back rounded vowels. [Work supported by NSFC No. 61573254.]