arXiv subjects

Pascal Perrier

Publications and source records attributed to Pascal Perrier.

24 records · Page 2Linked to original sources

arXiv2006

Modeling the production of VCV sequences via the inversion of a biomechanical model of the tongue

A control model of the production of VCV sequences is presented, which consists in three main parts: a static forward model of the relations between motor commands and acoustic properties; the specification of targets in the perceptual space; a planning procedure based on optimization principles. Examples of simulations generated with this model illustrate how it can be used to assess theories and models of coarticulation in speech.

physics.med-ph↗

arXiv2006

A non-invasive device to measure mechanical interaction between tongue, palate and teeth during speech production

This paper describes an original experimental procedure to measure the mechanical interaction between the tongue and teeth and palate during speech production. It consists in using edentulous people as subjects and to insert pressure sensors in the structure of their complete dental prosthesis. Hence, there is no perturbation of the vocal tract cavity due to the sensors themselves. Several duplicates are used with transducers situated at different locations of the complete denture according to palatography's results, in order to carefully analyze the production of specific sounds such as stop consonants.. It is also possible to measure the contact pressure at different locations on the palate for the same sound.

physics.med-ph↗

arXiv2006

Physical modelling of the airflow-walls interactions to understand the sleep apnea syndrome

Sleep Apnea Syndrome (SAS) is defined as a partial or total closure of the patient upper airways during sleep. The term "collapsus" (or collapse) is used to describe this closure. From a fluid mechanical point of view, this collapse can be understood as a spectacular example of fluid-walls interaction. Indeed, the upper airways are delimited in their largest part by soft tissues having different geometrical and mechanical properties: velum, tongue and pharyngeal walls. Airway closure during SAS comes from the interaction between these soft tissues and the inspiratory flow. The aim of this work is to understand the physical phenomena at the origin of the collapsus and the metamorphosis in inspiratory flow pattern that has been reported during SAS. Indeed, a full comprehension of the physical conditions allowing this phenomenon is a prerequisite to be able to help in the planning of the surgical gesture that can be prescribed for the patients. The work presented here focuses on a simple model of fluid-walls interactions. The equations governing the airflow inside a constriction are coupled with a Finite Element (FE) biomechanical model of the velum. The geometries of this model is extracted from a single midsagittal radiography of a patient. The velar deformations induced by airflow interactions are computed, presented, discussed and compared to measurements collected onto an experimental setup.

physics.med-ph↗

arXiv2006

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. For this, a generic three-dimensional model of the face is automatically adapted to the morphology of the patient by the mean of elastic registration. Qualitative simulations of the consequences of an osteotomy of the mandible can thus be provided. The second model addresses the Sleep Apnoea Syndrome. Its aim is to develop a complete modelling of the interaction between airflow and upper airways walls during respiration. Dynamical simulations of the interaction during a respiratory cycle are computed and compared with observed phenomena.

physics.med-ph↗

arXiv2006

A 3D dynamical biomechanical tongue model to study speech motor control

A 3D biomechanical dynamical model of human tongue is presented, that is elaborated in the aim to test hypotheses about speech motor control. Tissue elastic properties are accounted for in Finite Element Modeling (FEM). The FEM mesh was designed in order to facilitate the implementation of muscle arrangement within the tongue. Therefore, its structure was determined on the basis of accurate anatomical data about the tongue. Mechanically, the hypothesis of hyperelasticity was adopted with the Mooney-Rivlin formulation of the strain energy function. Muscles are modeled as general force generators that act on anatomically specified sets of nodes of the FEM structure. The 8 muscles that are known to be largely involved in the production of basic speech movements are modeled. The model and the solving of the Lagrangian equations of movement are implemented using the ANSYSTM software. Simulations of the influence of muscle activations onto the tongue shape are presented and analyzed.

physics.med-ph↗

arXiv2006

Influences of tongue biomechanics on speech movements during the production of velar stop consonants: a modeling study

This study explores the following hypothesis: forward looping movements of the tongue that are observed in VCV sequences are due partly to the anatomical arrangement of the tongue muscles and how they are used to produce a velar closure. The study uses an anatomically based 2D biomechanical tongue model. Tissue elastic properties are accounted for in finite-element modeling, and movement is controlled by constant-rate control parameter shifts. Tongue raising and lowering movements are produced by the model with the combined actions of the genioglossus, styloglossus and hyoglossus. Simulations of V1CV2 movements were made, where C is a velar consonant and V is [a], [i] or [u]. If V1 is one of the vowels [a] and [u], the resulting trajectories describe movements that begin to loop forward before consonant closure and continue to slide along the palate during the closure. This prediction is in agreement with classical data published in the literature. If V1 is vowel [i], we observe a small backward movement. This is also in agreement with some measurements on human speakers, but it is also in contradiction with the original data published by Houde (1967). These observations support the idea that the biomechanical properties of the tongue could be the main factor responsible for the forward loops when V1 is a back vowel. In the left [i] context, it seems that additional factors have to be taken into considerations, in order to explain the observations made on some speakers

physics.med-ph↗