Biomechanics of fundamental frequency regulation: Constitutive modeling of the vocal fold lamina propria

Accurate characterization of biomechanical characteristics of the vocal fold is critical for understanding the regulation of vocal fundamental frequency (F0), which depends on the active control of the intrinsic laryngeal muscles as well as the passive biomechanical response of the vocal fold lamina propria. Specifically, the tissue stress-strain response and viscoelastic properties under cyclic tensile deformation are relevant, when the vocal folds are subjected to length and tension changes due to posturing. This paper describes a constitutive modeling approach quantifying the relationship between vocal fold stress and strain (or stretch), and establishes predictions of F0 with the string model of phonation based on the constitutive parameters. Results indicated that transient and time-dependent changes in F0, including global declinations in declarative sentences, as well as local F0 overshoots and undershoots, can be partially attributed to the time-dependent viscoplastic response of the vocal fold cover.