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

Cross-calibration of Time-of-flight and Colour Cameras

Time-of-flight cameras provide depth information, which is complementary to the photometric appearance of the scene in ordinary images. It is desirable to merge the depth and colour information, in order to obtain a coherent scene representation. However, the individual cameras will have different viewpoints, resolutions and fields of view, which means that they must be mutually calibrated. This paper presents a geometric framework for this multi-view and multi-modal calibration problem. It is shown that three-dimensional projective transformations can be used to align depth and parallax-based representations of the scene, with or without Euclidean reconstruction. A new evaluation procedure is also developed; this allows the reprojection error to be decomposed into calibration and sensor-dependent components. The complete approach is demonstrated on a network of three time-of-flight and six colour cameras. The applications of such a system, to a range of automatic scene-interpretation problems, are discussed.Comment: 18 pages, 12 figures, 3 table

Citations cervantines en France

Citazioni francesi di Cervantes, nella lingua contemporanea o in quella letteraria, sono piuttosto rare. Eppure i nomi di tre ‘tipi' cervantini – une dulcinée , un don Quichotte e (in minor misura) une maritorne – hanno avuto una lunga permanenza nella lingua francese, anche fra chi non ha mai letto Cervantes. Si analizzano alcune occorrenze di queste 'antonomasie' e quindi ci si sofferma sul proverbio il faut laisser le temps au temps, utilizzato almeno in un'occasione dal presidente François Mitterand: il suo debito nei confronti di Cervantes può essere considerato una congettura aperta, a differenza di quanto sostenuto su Internet.Both in contemporary and literary French, quotations from Cervantes are quite rare. And yet, the names of three of his character types (une dulcinée, un don Quichotte, and – to a lesser extent – une maritorne) have been popular for a long time in this language, even among people unfamiliar with Cervantes. In the first place, I aim to analyze some occurrences of these 'antonomasias'. I will then focus on the proverb il faut laisser le temps au temps – used at least once by President François Mitterrand – in order to argue that his debt to Cervantes can be considered an open conjecture, contrary to what Internet sources often claim

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

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

Modeling Vocal Fold Motion with a New Hydrodynamic Semi-Continuum Model

Vocal fold (VF) motion is a fundamental process in voice production, and is also a challenging problem for direct numerical computation because the VF dynamics depend on nonlinear coupling of air flow with the response of elastic channels (VF), which undergo opening and closing, and induce internal flow separation. A traditional modeling approach makes use of steady flow approximation or Bernoulli's law which is known to be invalid during VF opening. We present a new hydrodynamic semi-continuum system for VF motion. The airflow is modeled by a quasi-one dimensional continuum aerodynamic system, and the VF by a classical lumped two mass system. The reduced flow system contains the Bernoulli's law as a special case, and is derivable from the two dimensional compressible Navier-Stokes equations. Since we do not make steady flow approximation, we are able to capture transients and rapid changes of solutions, e.g. the double pressure peaks at opening and closing stages of VF motion consistent with experimental data. We demonstrate numerically that our system is robust, and models in-vivo VF oscillation more physically. It is also much simpler than a full two-dimensional Navier-Stokes system.Comment: 27 pages,6 figure

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

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