Modelling and validation of the non-linear elastic stress-strain behaviour of multi-layer silicone composites.

Multi-layer silicone composites are commonly used to mold deformable silicone vocal folds replicas. Nevertheless, so far the stress-strain characterisation of such composite specimens is limited to their effective Young's modulus (up to 40 kPa) characterising the elastic low-strain range, i.e.

Experimental study on the quasi-steady approximation of glottal flows.

To examine the quasi-steady approximation of the glottal flow, widely used in the modeling of vocal fold oscillations, intraglottal pressure distributions were measured in a scaled-up static vocal fold model under time-varying flow conditions. The left and right vocal folds were slightly open and set to a symmetric and oblique configuration with a divergence angle. To realize time-varying flow conditions, the flow rate was sinusoidally modulated with a frequency of 2 and 10 Hz, which correspond to 112.

Multimodal radiation impedance of a waveguide with arbitrary cross-sectional shape terminated in an infinite baffle.

Simulations of waveguide acoustics require a description of the boundary condition at the open end. For problems involving higher order transverse modes, it is often described by a multimodal radiation impedance matrix. Expressions for the computation of this matrix for an infinite flange condition are available only for circular and rectangular cross-sectional shapes.

Threshold of oscillation of a vocal fold replica with unilateral surface growths.

Among vocal fold diseases, the presence of a surface growth is often encountered and can be considered a public health issue. While more energy is required to achieve phonation than in healthy cases, this situation can lead to a wide range of voice perturbations, from a change of voice quality to aphonia. The present study aims at providing finer comprehension of the physical phenomena underlying this type of pathological phonation process.

Influence of vocal tract geometry simplifications on the numerical simulation of vowel sounds.

For many years, the vocal tract shape has been approximated by one-dimensional (1D) area functions to study the production of voice. More recently, 3D approaches allow one to deal with the complex 3D vocal tract, although area-based 3D geometries of circular cross-section are still in use. However, little is known about the influence of performing such a simplification, and some alternatives may exist between these two extreme options.

Influence of lips on the production of vowels based on finite element simulations and experiments.

Three-dimensional (3-D) numerical approaches for voice production are currently being investigated and developed. Radiation losses produced when sound waves emanate from the mouth aperture are one of the key aspects to be modeled. When doing so, the lips are usually removed from the vocal tract geometry in order to impose a radiation impedance on a closed cross-section, which speeds up the numerical simulations compared to free-field radiation solutions.

Modeling of aerodynamic interaction between vocal folds and vocal tract during production of a vowel-voiceless plosive-vowel sequence.

The context of this study is the physical modeling of speech production. The objective is, by using a mechanical replica of the vocal tract, to test quantitatively an aerodynamic model of the interaction between the vocal folds and the vocal tract during the production of a vowel-voiceless plosive-vowel sequence. The first step is to realize acoustic and aerodynamic measurements on a speaker during the production of an /apa/ sequence.

Self-entrainment of the right and left vocal fold oscillators.

This article presents an analysis of entrained oscillations of the right and left vocal folds in the presence of asymmetries. A simple one-mass model is proposed for each vocal fold. A stiffness asymmetry and open glottis oscillations are considered first, and regions of oscillation are determined by a stability analysis and an averaging technique.

Effects of higher order propagation modes in vocal tract like geometries.

In this paper, a multimodal theory accounting for higher order acoustical propagation modes is presented as an extension to the classical plane wave theory. This theoretical development is validated against experiments on vocal tract replicas, obtained using a 3D printer and finite element simulations. Simplified vocal tract geometries of increasing complexity are used to investigate the influence of some geometrical parameters on the acoustical properties of the vocal tract.

Influence of glottal cross-section shape on phonation onset.

Phonation models commonly rely on the assumption of a two-dimensional glottal geometry to assess kinetic and viscous flow losses. In this paper, the glottal cross-section shape is taken into account in the flow model in order to capture its influence on vocal folds oscillation. For the assessed cross-section shapes (rectangular, elliptical, or circular segment) the minimum pressure threshold enabling to sustain vocal folds oscillation is altered for constriction degrees smaller than 75%.

The influence of glottal cross-section shape on theoretical flow models.

Physical and mathematical phonation models commonly rely on a quasi-one-dimensional flow model. The assumption of quasi-one-dimensional flow through a glottis with fixed length is analyzed for different cross-section shapes: Circle, rectangle, ellipse, and circular segment. A simplified flow model is formulated which accounts for kinetic losses, viscosity, and cross-section shape.

Experimental validation of flow models for a rigid vocal tract replica.

Flow through the vocal tract is studied through an in vitro rigid replica for different geometrical configurations and steady flow conditions with bulk Reynolds numbers Re<15,000. The vocal tract geometry is approximated by two consecutive obstacles, representing "tongue" and "tooth," in a rectangular channel of fixed length. For the upstream tongue obstacle with fixed constriction degree (81%) the streamwise position is varied and for the downstream obstacle the constriction degree is varied from 0% up to 96%.

A lumped mucosal wave model of the vocal folds revisited: recent extensions and oscillation hysteresis.

This paper examines an updated version of a lumped mucosal wave model of the vocal fold oscillation during phonation. Threshold values of the subglottal pressure and the mean (DC) glottal airflow for the oscillation onset are determined. Depending on the nonlinear characteristics of the model, an oscillation hysteresis phenomenon may occur, with different values for the oscillation onset and offset threshold.

Vocal fold and ventricular fold vibration in period-doubling phonation: physiological description and aerodynamic modeling.

Occurrences of period-doubling are found in human phonation, in particular for pathological and some singing phonations such as Sardinian A Tenore Bassu vocal performance. The combined vibration of the vocal folds and the ventricular folds has been observed during the production of such low pitch bass-type sound. The present study aims to characterize the physiological correlates of this acoustical production and to provide a better understanding of the physical interaction between ventricular fold vibration and vocal fold self-sustained oscillation.

Experimental validation of quasi-one-dimensional and two-dimensional steady glottal flow models.

Physical modelling of phonation requires a mechanical description of the vocal fold coupled to a description of the flow within the glottis. In this study, an in-vitro set-up, allowing to reproduce flow conditions comparable to those of human glottal flow is used to systematically verify and discuss the relevance of the pressure and flow-rate predictions of several laminar flow models. The obtained results show that all the considered flow models underestimate the measured flow-rates and that flow-rates predicted with the one-dimensional model are most accurate.

Influence of a constriction in the near field of the vocal folds: physical modeling and experimental validation.

The involvement of the ventricular folds is often observed in human phonation and, in particular, in pathological and or some throat-singing phonation. This study aims to explore and model the possible aerodynamic interaction between the ventricular and vocal folds using suitable in vitro setups allowing steady and unsteady flow conditions. The two experimental setups consist of a rigid and a self-oscillating vocal-fold replica, coupled to a downstream rigid ventricular-fold replica in both cases.

Theoretical simulation and experimental validation of inverse quasi-one-dimensional steady and unsteady glottal flow models.

In physical modeling of phonation, the pressure drop along the glottal constriction is classically assessed with the glottal geometry and the subglottal pressure as known input parameters. Application of physical modeling to study phonation abnormalities and pathologies requires input parameters related to in vivo measurable quantities commonly corresponding to the physical model output parameters. Therefore, the current research presents the inversion of some popular simplified flow models in order to estimate the subglottal pressure, the glottal constriction area, or the separation coefficient inherent to the simplified flow modeling for steady and unsteady flow conditions.

An in vitro setup to test the relevance and the accuracy of low-order vocal folds models.

An experimental setup and human vocal folds replica able to produce self-sustained oscillations are presented. The aim of the setup is to assess the relevance and the accuracy of theoretical vocal folds models. The applied reduced mechanical models are a variation of the classical two-mass model, and a simplification inspired on the delayed mass model for which the coupling between the masses is expressed as a fixed time delay.

Biomechanical models to simulate consequences of maxillofacial surgery.

This paper presents the biomechanical finite element models that have been developed in the framework of the computer-assisted maxillofacial surgery. After a brief overview of the continuous elastic modelling method, two models are introduced and their use for computer-assisted applications discussed. The first model deals with orthognathic surgery and aims at predicting the facial consequences of maxillary and mandibular osteotomies.