Experimental validation of some additional issues in physical vocal folds models

Insight in vocal folds oscillation mechanisms is important in the understanding of phonation, the synthesiz-ing of voiced sound and the study of voice disorders. In general, simplifications of the physical ongoing 3D fluid-structure interaction between the living tissues and the airflow are favoured. Several simple models (lumped models) are obtained by representing the vocal folds as a distribution of elastic mass(es). The mass-spring-damper system is acted on by a driving force resulting from the pressure exerted by the intra-glottal airstream. The outcome of theoretical models is 'in-vitro' validated using rigid or deformable vocal fold replicas mounted in a suitable experimental set-up. Previous research focused on the prediction of the phonation pressure threshold and oscillation frequency of the 'in-vitro' replica in absence and presence of acoustical feedback whereas in the theoretical model a vocal fold is represented by one or two masses. The model yielded accurate prediction of the oscillation threshold and frequency. In this paper we present a new in-vitro set-up which allows to overcome some limitations of this previous study. Thanks to the use of a digital camera synchronised with a light source and pressure sensors this set-up allows 1) to measure the area of the vocal folds opening and 2) to impose independent initial conditions as e.g. height of the initial opening and internal pressure in the vocal fold replica. Preliminary results are presented and their impact on physical modelling are discussed.