INFLUENCE OF TISSUE CHANGES IN SUPERFICIAL LAMINA PROPRIA ON PRODUCTION OF CZECH VOWELS

Abstract

: Superficial lamina propria (SLP) is a water-like vocal fold (VF) layer located directly under over-lying epithelium. Its material properties affect VF motion and thus resulting spectrum of produced sound. Influence of stiffness and damping of the SLP on sound spectrum of Czech vowels is examined using a two-dimensional (2D) finite element (FE) model of a human phonation system. The model consists of the VF (structure model) connected with an idealized trachea and vocal tract (VT) (fluid models). Five VTs for all Czech vowels [a:], [e:], [i:], [o:] and [u:] were used and their geometry were based on MRI data. Fluid flow in the trachea and VT was modelled by unsteady viscous compressible Navier-Stokes equations. Such a formu-lation enabled numerical simulation of a fluid-structure-acoustic interaction (FSAI). Self-sustained oscillations of the VF were described by a momentum equation including large deformations and a homogeneous linear elastic model of material was used. Fluid and structure solvers exchange displacements and boundary forces in each iteration. During closed phase VFs are in contact and fluid flow is separated. We can observe that both the damping and the stiffness of the SLP substantially influence the amplitude and frequency of VFs vibration as well as the open time of the glottis.