Towards models of phonation

Abstract

The earliest models of phonation were based on the assumption that the glottis is closed during a part of the vibration cycle, that is, the phonation is modal. Nonmodal phonation, however, commonly occurs not only for disordered voice but also for normal voices, which often exhibit a breathy quality or irregular vibration. In this paper, we review recent work that examines acoustic data and models of nonmodal phonation in both normal and disordered voice. We first describe acoustic models that predict how the glottal source varies from modal phonation to phonation resulting from glottal configurations that are partially abducted, including a posterior glottal opening. These models are applied first to vowels of nondisordered adults, and, later in the paper, to vowels produced by adults with dysarthria. We also present results from a study in which a modified version of the two-mass model is used to resolve a seeming conflict among aerodynamic and acoustic data collected from adult female subjects with vocal-fold nodules. Some discussion of nonmodal phenomena that occur due to prosodic and emotional influences is included. Overall, it appears that current models of modal phonation can be extended to include a range of nonmodal phonation types.