ACOUSTIC COUPLING IN PHONATION AND ITS EFFECT ON ...

152.1.4 Self-oscillating models of phonationSelf-sustained models of the vocal folds are designed to provide insights intothe mechanisms that control phonation in normal and pathological cases. Lowdimensionalmodels are more commonly used, as they efficiently capture the mostdominant modes of vibration and are expected to reproduce many fundamental aspectsof phonation with acceptable accuracy. Validation of these and other models ofphonation continues to be an important research topic in the field.The first low-order models were the single-mass [45] and two-mass models [46],that made use of van den Berg’s glottal resistance [78] along with a glottal inertanceand simplified versions of the vocal tract and subglottal system. Even though manycomponents of the original two-mass model (herein referred to as IF72) have beenshown to misrepresent the glottal aerodynamics, mechanical properties, and energytransfer [5, 6,59], the model continues to be one of the most significant and highlyreferenced models of phonation.Some improvements of IF72 have included a different solution for the flow equation,that was shown to be more stable and better handled time-varying flow andirregular geometries [59]. A method to correct for discrepancies found in the locationof the separation point was implemented in a modified version of IF72 [85]. Inaddition, this study proposed the idea of a pre-collision mechanism to minimize theexcessively abrupt closing observed in IF72. An asymmetric implementation of IF72was developed to model superior and recurrent nerve paralysis [92]. The model wassimplified version of IF72 that neglected its viscous effects, glottal inertance, nonlinearspring constants, and acoustic coupling. However, this model has been repeatedlyused to study asymmetric and chaotic behavior within the glottis [93,94] and has beenextended using more complex flow solvers [95].A complete adaptation of IF72 was performed to include a third degree of freedom[42], which helped to better modeling of the mucosal wave and more accuratelyrepresent physiological aspects [96]. This “body-cover” model (herein referred to as