Degree of vocal fold adduction affects listener perception of simulated laryngeal vocal tremor

Laryngeal vocal tremor (VT) is a neurogenic voice disorder characterized by modulation of the fundamental frequency (f_o) and intensity. The primary medical treatment for VT is laryngeal botulinum toxin injections, which result in temporarily reduced speaker- and listener-perceived VT severity. These injections also cause temporary breathiness, which is conventionally considered an adverse effect of the treatment. However, previous studies using a computational model of VT revealed that listeners perceived modulated voices as less “shaky” when the vocal quality was breathy, even when the extent of f_o modulation was the same. The purpose of the current study is to assess the effect of breathiness on listener perception of VT across a range of modulation extents. A kinematic model of the vocal folds and wave-reflection model of the vocal tract were used to simulate VT with degrees of vocal fold adduction representing a spectrum of normal to breathy voice and with f_o modulation extents ranging from 0%–10%. Normal hearing listeners will be presented with pairs of stimuli differing by degree of vocal fold adduction and will be asked to identify which vowel is “shakier.” The findings of this study could inform selection of treatment targets and candidates for behavioral therapy for VT.