Effects of false vocal fold adduction and aryepiglottic sphincter narrowing on the voice source in a three-dimensional voice production model.

Although voice production often involves false vocal fold (FVF) adduction and aryepiglottic sphincter (AES) narrowing, their effects on the voice source still remain unclear. In this study, a three-dimensional (3D) compressible flow simulation coupled to a two-mass vocal fold model in a vocal tract with varying degrees of constriction at the levels of the FVF and AES is conducted. Results showed a small effect of FVF adduction and AES narrowing on the voice source except when the FVFs were strongly adducted. Strong FVF adduction reduced the glottal resistance and increased the transglottal pressure, thus strengthening the voice source. This reduction in glottal resistance is a result of the glottal jet persisting longer into the supraglottal region, which can be achieved by constricting the jet from the medial-lateral direction. In contrast, constricting the jet flow from the anterior-posterior direction had almost no influence on the source strength. In summary, the effect of the 3D supraglottal flow features on the voice source is small except for extreme FVF adduction, and the effect of epilaryngeal adduction is mainly on the vocal tract transfer function rather than the voice source.