Experimental Validation of Simplified Free Jet Turbulence Models Applied to the Vocal Tract

Sound production due to turbulence is widely shown to be an important phenomenon involved in a.o. fricatives, singing, whispering and speech pathologies. In spite of its relevance turbulent flow is not considered in classical physical speech production models mostly dealing with voiced sound production. The current study presents preliminary results of an experimental validation of simplified turbulence models in order to estimate the time-mean velocity distribution in a free jet downstream of a tube outlet. Aiming a future application in speech production the influence of typical vocal tract shape parameters on the velocity distribution is experimentally and theoretically explored: the tube shape, length and the degree and geometry of the constriction. Simplified theoretical predictions are obtained by applying similarity solutions of the bidimensional boundary layer theory to a plane and circular free jet in still air. The orifice velocity and shape are the main model input quantities. Results are discussed with respect to the upper airways and human sound production.Comment: 6 pages; 19th International Congress on Acoustics, Madrid : Espagne (2007

Experimental validation and physical modelling of vocal folds pathologies

Voiced sounds involve self-sustained vocal folds oscillations due to the interaction between the airflow and the vocal folds. Common vocal folds pathologies like polyps and anatomical asymmetry degrade the mechanical vocal fold properties and consequently disturb the normal oscillation pattern resulting in an abnormal sound production. Treatment of voice abnormalities would benefit from an improved understanding between the pathology and the resulting oscillation pattern which motivates physical vocal folds modelling. The current study applies a theoretical vocal folds model to vocal folds pathologies. The theoretical vocal folds model is validated using an experimental set-up simulating the human phonatory apparatus. It consists in a pressure reservoir, a self-oscillating latex replica of the vocal folds and an acoustical resonator. The effects of pathologies are simulated by modifying the replica's geometry, elasticity, and homogeneity under controlled experimental conditions. In general, we observed a close match between measurements and theoretical predictions, which is all the more surprising considering the crudeness of the theoretical mode

Physical modeling of bilabial plosives production

International audienceThe context of this study is the physical modeling of speech production. The first step of our approach is to realize in-vivo measurements during the production of the vowel-consonant-vowel sequence /apa/. This measurements concerns intra-oral pressure, acoustic pressure radiated at the lips and labial parameters (aperture and width of the lips) derived from a high-speed video recording of the subject face. In a second time, theoretical models from speech production literature are under investigation to predict the air flow trough the lips. A model is validated by comparing his predictions with results obtained from measurements on a replica of phonatory system. Then, the same experimental set-up is used to introduce an aerodynamic model of supraglottal cavity expansion. Finally, we achieve numerical simulations of a vowel-bilabial plosive-vowel utterance, by using these models. Simulation results highlight the influence of the cheeks expansion during the production of bilabial plosives

Techniques expérimentales pour la caractérisation mécanique de maquettes in vitro de cordes vocales

National audienceLa validation des modèles élaborés en production vocale nécessite la mise au point de dispositifs in-vitro simples mais pouvant reproduire des phénomènes physiques impliqués dans la production vocale humaine. Depuis les travaux de Van den Berg (1957), de nombreuses maquettes ont été développées avec une complexité croissante. Dans cette communication, nous nous intéressons à la caractérisation mécanique des structures vibrantes, dont la connaissance est indispensable à la reproductibilité et la répétabilité des mesures ultérieures sur la maquette ainsi qu'à l'analyse des résultats. Plusieurs techniques expérimentales sont testées sur une maquette de cordes vocales. Les résultats sont comparés en fonction des différents principes de mesure (vibrométrie laser, mesure de l'ouverture glottique, accéléromètres piézo-électriques), actionneurs (pot vibrant et source acoustique) et types d'excitation (fréquence par fréquence, sinus glissant et bruit large bande)

Etude de l'Effet de Masses Ajoutées sur la Production de Sons Voisés

National audienceL'objectif de ce travail est la compréhension et la modélisation physique des troubles de la voix associés à la présence d'excroissances à la surface d'un ou des deux plis vocaux. Si les conséquences de la présence de kystes, nodules et polypes ont été largement étudiées du point de vue perceptif avec des descripteurs essentiellement basés sur le signal acoustique, nous nous intéressons ici à la compréhension de l'origine des phénomènes physiques sous-jacents à la production normale ou pathologique de la voix. La présence d'une excroissance peut mener à des perturbations diverses, comme une modification locale de masse volumique ou d'élasticité des tissus biologiques, une mise en concurrence dues à l'asymétrie entre les plis, et/ou un changement substantiel de l'écoulement glottique. Une réplique expérimentale en latex des cordes vocales a été élaborée, permettant un maintien et un positionnement de masses rigides de dimension et masse variables. Des caractérisations mécaniques et des mesures de seuils d'oscillation ont été réalisées. Ces résultats sont comparés à ceux issus de simulations et d'analyse linéaire de stabilité sur une extension du modèle simplifié à deux masses

Modelling the human pharyngeal airway: validation of numerical simulations using in vitro experiments

In the presented study, a numerical model which predicts the flow-induced collapse within the pharyngeal airway is validated using in vitro measurements. Theoretical simplifications were considered to limit the computation time. Systematic comparisons between simulations and measurements were performed on an in vitro replica, which reflects asymmetries of the geometry and of the tissue properties at the base of the tongue and in pathological conditions (strong initial obstruction). First, partial obstruction is observed and predicted. Moreover, the prediction accuracy of the numerical model is of 4.2% concerning the deformation (mean quadratic error on the constriction area). It shows the ability of the assumptions and method to predict accurately and quickly a fluid-structure interaction

Laser scanning vibrometry and modal analysis to characterize a vocal fold replica

International audienceVocal folds are composed of elastic, soft, multilayer material, and are set to various vibration regimes during phonation, while speaking or singing. To explore such vibration phenomena, a vocal folds replica has been built, allowing to control physical parameters (subglottal pressure, vocal folds stiffness, and glottal aperture) in order to understand their respective contribution. Vocal folds are imitated by latex tubes filled with water under variable pressure. The present study aims at presenting mechanical measurements performed on a single vocal fold replica by means of a shaker provided with an accelerometer in conjunction with a laser vibrometer. This vibration measurement protocol yields a series of frequency response functions over a specific area of the vocal fold. Modal analysis is then performed using an algorithm based on the least square complex exponentials (LSCE) method, which has been developed for single input-multiple output (SIMO) systems. Results are further compared with those from the rational fraction polynomial (RFP) method. Although results are in fair accordance, the observed discrepancies are quantified and discussed

Hydro-elastic finite element model of a vocal fold replica

International audienceExperimental vocal fold replicas are currently used in speech production studies in order to validate simplified models on controllable devices. In addition to in-situ mechanical characterization, it is important to be able to understand their behavior when changing assembly properties or using parameters control to tune the folds, by developing a model able to predict their static and dynamic motions. This also enables to describe more complex vibration behaviors which could be harder to observe experimentally. This paper first presents a hydro-elastic finite element model of a single vocal fold. Numerical results are discussed, along with a parametric analysis. Then this model is extended to take into account the effect of the water pressure on the inflation of the folds and on the resonance frequencies. A hyper-elastic calculation is first used to simulate the latex inflation. An updated Lagrangian approach processes it as a pre-stress term in a modal analysis calculation for the small amplitude vibrations of the hydro-elastic structure, which allows to model the water pressure influence on the mechanical resonances of the simulated replica