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Viallet G.,Ecole de Technologie Superieure of Montreal | Sgard F.,IRSST | Laville F.,Ecole de Technologie Superieure of Montreal | Nelisse H.,Ecole de Technologie Superieure of Montreal
Applied Acoustics | Year: 2015

Several studies report that an important range of attenuation can be observed in the measurement of earplugs (EP) sound attenuation. This important range of attenuation can be attributed to several intricate factors; the most commonly cited being the earplug insertion depth, the presence of leakages, the inter-subject ear canal (EC) geometrical variations, and the dynamical properties of the human EC tissues. The purpose of this work is to investigate the effect of these individual factors on the insertion loss (IL). Firstly, a finite element model of the EC surrounded by human external tissues and occluded by two types of EPs (foam and custom molded) is developed to predict the IL. Secondly, comparisons between attenuation measurement on human subjects and IL predicted by the model are carried out to validate the model. Thirdly, the effect of the aforementioned factors is quantified using the proposed model in order to explain the variability observed in the attenuation measurement on human subjects. It is found that the presence of leakages and the EP insertion depth are mainly responsible for the variability of the predicted EPs IL at frequencies

Brummund M.K.,Ecole de Technologie Superieure of Montreal | Sgard F.,IRSST | Petit Y.,Ecole de Technologie Superieure of Montreal | Laville F.,Ecole de Technologie Superieure of Montreal
Journal of the Acoustical Society of America | Year: 2014

A linear three-dimensional (3D) elasto-acoustic finite element model was used to simulate the occlusion effect following mechanical vibration at the mastoid process. The ear canal and the surrounding soft and bony tissues were reconstructed using images of a female cadaver head (Visible Human Project ®). The geometrical model was coupled to a 3D earplug model and imported into comsol Multiphysics (COMSOL®, Sweden). The software was used to solve for the sound pressure at the eardrum. Finite element modeling of the human external ear and of the occlusion effect has several qualities that can complement existing measuring and modeling techniques. First, geometrically complex structures such as the external ear can be reconstructed. Second, various material behavioral laws and complex loading can be accounted for. Last, 3D analyses of external ear substructures are possible allowing for the computation of a broad range of acoustic indicators. The model simulates consistent occlusion effects (e.g., insertion depth variability). Comparison with an experimental dataset, kindly provided by Stenfelt and Reinfeldt [Int. J. Audiol. 46, 595-608 (2007)], further demonstrates the model's accuracy. Power balances were used to analyze occlusion effect differences obtained for a silicone earplug and to examine the increase in sound energy when the ear canal is occluded (e.g., high-pass filter removal). © 2014 Acoustical Society of America.

Thebault J.,CREAPT CEE France | Gaudart C.,French National Center for Scientific Research | Cloutier E.,IRSST | Volkoff S.,CREAPT CEE France
Work | Year: 2012

Objectives: This article presents the results of a study currently underway looking at the transmission of vocational skills between health care workers in a French hospital. The aim was to show that health care workers, in addition to their work with patients, also have to incorporate the transmission of vocational skills into their daily activities. Methods: Thirteen transmission situations were observed and analyzed by means of an activity-focused ergonomic work analysis, with the aim of reporting on this "invisible work". Participants: The population studied was composed of nurses and the nursing assistants from three different units in one hospital. Results: The results show that the work required to integrate and supervise new staff members is left to the discretion of health care workers. This means they are constantly required to arbitrate on both an individual and collective basis between providing health care for patients and supporting new members of staff. The content of the transmission goes beyond the prescribed tasks and technical knowledge, as staff members also pass on their professional strategies (individual and collective), rules of practice and ethical considerations. Supervising students also offers experienced workers the opportunity to share their professional practices. Conclusions: This study highlights the issues arising from this transmission activity for the experienced workers, new workers, patients and the hospital. © 2012 - IOS Press and the authors. All rights reserved.

Sgard F.,IRSST | Castel F.,Renault S.A. | Atalla N.,Universite de Sherbrooke
Applied Acoustics | Year: 2011

The paper discusses the sound absorptive performance of a porous material with meso-perforations inserted in a rectangular waveguide using a numerical hybrid adaptive finite element-modal method. Two specific applications are investigated: (i) the improvement of porous materials noise reduction coefficient using meso-perforations (ii) the effects of lateral air gaps on the normal incidence sound absorption of mono-layer and two-layer porous materials. For the first application, a numerical design of experiments is used to optimize the sound performance of a porous material with meso-perforations with a reduced number of numerical simulation. An example in which the optimization process is carried out on the thickness and size of the perforation is presented to illustrate the relevance of the approach. For the second application, a set of twenty fibrous materials spanning a large flow resistivity range is used. Practical charts are proposed to evaluate the influence of air gaps on the average sound absorption performance of porous materials. This is helpful to both the experimenter regarding characterization of porous material based on Standing Wave Tube measurements and for the engineer to quantifying the impact of air gaps and for designing efficient absorbers. © 2010 Elsevier Ltd. All rights reserved.

Becot F.-X.,MATELYS | Jaouen L.,MATELYS | Sgard F.,IRSST
Noise Control Engineering Journal | Year: 2011

This paper examines the potential of using composite porous materials to design robust noise control packages. Composite porous are meso-perforated porous materials in which perforations are filled with another porous material. The work presented here shows that the association of two carefully selected materials could lead to interesting combined properties of sound absorption and sound insulation. A canonical plate/cavity system excited with an internal acoustic source is chosen to illustrate the potential of these materials for noise enclosures. The coupled problem is solved using Finite Element Method. The sound propagation in composite porous materials is described by Biot-Allard's poroelasticity equations. Noise reductions obtained using composite porous are compared to those obtained using homogeneous materials. The sound powers dissipated into the system are also examined to give further insights into the physics of the involved phenomena. The results show that the achieved performances take full benefit of the efficiencies of either materials which form the composite porous for different frequency ranges. © 2011 Institute of Noise Control Engineering.

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