Mechanisms of modal and nonmodal phonation

Modal and nonmodal phonation are contrasted from the perspective of voice production. It is shown that vocal fold vibrations from both types of phonation may be formed from just a few basic building blocks, called eigenmodes. Signi"cantly, modal and nonmodal phonation may be distinguished based on the entrainment (i.e., synchronization) of the eigenmodes, where modal phonation corresponds to a 1 : 1 entrainment, and nonmodal corresponds to all more complex patterns. Indirect and direct investigations of eigenmode entrainment are reviewed, citing investigations from computer models, excised larynx experiments, and in vivo investigations on human subjects. Resonance studies of the vocal folds provide an indirect investigation of eigenmode entrainment, indicating which eigenmodes are most likely to entrain based on their natural frequencies. Challenging previous interpretations of the vocal fold resonance structure derived from the two-mass model, continuum models and in vivo studies on human subjects are beginning to converge on a similar description of the composite resonance. In addition, "nite element models and highspeed imaging studies of the medial surface of the vocal folds provide powerful, direct evidence of eigenmode entrainment in vocal fold vibration. Applications of these techniques are suggested for exploring speci"c entrainment mechanisms used in language. ( 2001 Academic Press