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Padois T.,École de Technologie Supérieure of Montreal | Sgard F.,IRSST | Doutres O.,École de Technologie Supérieure of Montreal | Berry A.,Université de Sherbrooke
Journal of Sound and Vibration | Year: 2017

Millions of workers are exposed to excessive noise levels each day. Acoustic solutions have to be developed to protect workers from hearing loss. The first step of an acoustic diagnosis is the source localization which can be performed with a microphone array. Spherical microphone arrays can be used to detect the acoustic source positions in a workplace. In this study, a spherical microphone array, with polyhedral discretization, is proposed and compared with a spherical array with a slightly different geometry. The generalized cross-correlation technique is used to detect the source positions. Moreover, two criteria are introduced to improve the noise source map. The first is based on the geometric properties of the microphone array and the scan zone whereas the second is based on the energy of the spatial likelihood function. Numerical data are used to provide a systematic comparison of both geometries and criteria. Finally, experiments in a reverberant room reveal that the polyhedral microphone array associated with both criteria provides the best noise source map. © 2016 Elsevier Ltd

Hamouda K.,Concordia University at Montréal | Rakheja S.,Concordia University at Montréal | Dewangan K.N.,NERIST | Marcotte P.,IRSST
Applied Ergonomics | Year: 2018

The vibration isolation performances of vibration reducing (VR) gloves are invariably assessed in terms of power tools’ handle vibration transmission to the palm of the hand using the method described in ISO 10819 (2013), while the nature of vibration transmitted to the fingers is ignored. Moreover, the VR gloves with relatively low stiffness viscoelastic materials affect the grip strength in an adverse manner. This study is aimed at performance assessments of 12 different VR gloves on the basis of handle vibration transmission to the palm and the fingers of the gloved hand, together with reduction in the grip strength. The gloves included 3 different air bladder, 3 gel, 3 hybrid, and 2 gel-foam gloves in addition to a leather glove. Two Velcro finger adapters, each instrumented with a three-axis accelerometer, were used to measure vibration responses of the index and middle fingers near the mid-phalanges. Vibration transmitted to the palm was measured using the standardized palm adapter. The vibration transmissibility responses of the VR gloves were measured in the laboratory using the instrumented cylindrical handle, also described in the standard, mounted on a vibration exciter. A total of 12 healthy male subjects participated in the study. The instrumented handle was also used to measure grip strength of the subjects with and without the VR gloves. The results of the study showed that the VR gloves, with only a few exceptions, attenuate handle vibration transmitted to the fingers only in the 10–200 Hz and amplify middle finger vibration at frequencies exceeding 200 Hz. Many of the gloves, however, provided considerable reduction in vibration transmitted to the palm, especially at higher frequencies. These suggest that the characteristics of vibration transmitted to fingers differ considerably from those at the palm. Four of the test gloves satisfied the screening criteria of the ISO 10819 (2013) based on the palm vibration alone, even though these caused amplification of handle vibration at the fingers. The fingers’ vibration transmission performance of gloves were further evaluated using a proposed finger frequency-weighting Wf apart from the standardized Wh-weighting. It is shown that the Wh weighting generally overestimates the VR glove effectiveness in limiting the fingers vibration in the high (H: 200–1250 Hz) frequency range. Both the weightings, however, revealed comparable performance of gloves in the mid (M: 25–200 Hz) frequency range. The VR gloves, with the exception of the leather glove, showed considerable reductions in the grip strength (27–41%), while the grip strength reduction was not correlated with the glove material thickness. It is suggested that effectiveness of VR gloves should be assessed considering the vibration transmission to both the palm and fingers of the hand together with the hand grip strength reduction. © 2017 Elsevier Ltd

Brummund M.K.,École de Technologie Supérieure of Montreal | Sgard F.,IRSST | Petit Y.,École de Technologie Supérieure of Montreal | Laville F.,École de Technologie Supérieure 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.

Ahmed J.,Kuwait Institute for Scientific Research | Varshney S.K.,Polymer Source Inc. | Janvier F.,IRSST
Journal of Thermal Analysis and Calorimetry | Year: 2014

Poly(l-lactide) (PLLA) and Poly(d-lactide) (PDLA) blended films (PLLA/PDLA) were prepared (5/95; 25/75; 50/50, and 75/25) by solvent casting method. Blend of PLLA and PDLA of medium molecular mass led to the formation of stereocomplex which was evidenced by differential scanning calorimetry, rheological measurement and Fourier transform infrared spectroscopy. The stereocomplex had a higher melting temperature (T m) (more than 50 C) and crystallized at higher temperature (T c) (more than 25 C) from the melt compared to neat PLLA and PDLA. The T m and T c gradually decreased with increasing the number of thermal scans. The enthalpy of fusion (δHm) for stereocomplex crystallites in 50/50 blend films was the highest than that of homo-crystallites. Rheological measurement at a temperature of 180-195 C revealed that the neat PLA was predominantly liquid-like behavior (G″ > G′) which transformed to extreme solid-like behavior by incorporation of PDLA into PLLA. Among blends, 50/50 PDLA/PLLA showed the maximum mechanical strength (G′) followed by 25/75, 75/25, and 5/95 blends. The significant increase in mechanical strength is believed to be attributed by stereocomplex formation by blends. Thermal and rheological data supported higher mechanical strength and an increase in melting and crystallization temperature adequately. © 2013 Akadémiai Kiadó, Budapest, Hungary.

PubMed | irsst, Institute National Of Sante Publique Du Quebec and University of Montréal
Type: Journal Article | Journal: Current oncology (Toronto, Ont.) | Year: 2016

More than 30 exposures in the workplace are proven carcinogens. In the present study, we aimed to estimate the burden of occupational cancer in Quebec so as to increase awareness among stakeholders and to prioritize research activities.Work-attributable fractions-that is, the proportions of cancers attributable to work-as published in Finland and the United Kingdom were applied to Quebec 2002-2006 cancer incidence and mortality data to estimate the number of work-related cases for 28 cancer sites.Overall, 6.0% of incident cancers (men: 9.1%; women: 2.7%) and 7.6% of cancer deaths (men: 11.8%; women: 2.8%) could be attributable to work, resulting annually in an average of 2160 new cancer diagnoses and 1190 cancer deaths in Quebec. Incident cancers of the lung, prostate, skin, bladder, and (female) breast were the most numerous; cancer sites resulting in more deaths were lung, (female) breast, and pleura. During the same period, compensation statistics reported annual averages of 94.3 incident cancers and 61.9 cancer deaths, mostly involving mesothelioma (64% of compensated incident cancers) and lung cancer (30% of compensated incident cancers).Increased recognition of workplace cancers by all stakeholders, from workers and employers to treating physicians, will foster appropriate preventive measures for safer workplaces.

Sgard F.,IRSST | Castel F.,Renault S.A. | Atalla N.,Université 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.

Viallet G.,École de Technologie Supérieure of Montreal | Sgard F.,IRSST | Laville F.,École de Technologie Supérieure of Montreal | Boutin J.,IRSST
Journal of the Acoustical Society of America | Year: 2014

Acoustical test fixtures (ATFs) are currently used to measure the attenuation of the earplugs. Several authors pointed out that the presence of an artificial skin layer inside the cylindrical ear canal of the ATFs strongly influenced the attenuation measurements. In this paper, this role is investigated via a 2D axisymmetric finite element model of a silicon earplug coupled to an artificial skin. The model is solved using COMSOL Multiphysics (COMSOL®, Sweden) and validated experimentally. The model is exploited thereafter to better understand the role of each part of the earplug/ear canal system and how the energy circulates within the domains. This is investigated by calculating power balances and by representing the mechanical and acoustical fluxes in the system. The important dissipative role of the artificial skin is underlined and its contribution as a sound transmission pathway is quantified. In addition, the influence of both the earplug and the artificial skin parameters is assessed via sensitivities analyses performed on the model. © 2014 Acoustical Society of America.

Viallet G.,École de Technologie Supérieure of Montreal | Sgard F.,IRSST | Laville F.,École de Technologie Supérieure of Montreal | Nelisse H.,École de Technologie Supérieure 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

Viallet G.,École de Technologie Supérieure of Montreal | Sgard F.,École de Technologie Supérieure of Montreal | Laville F.,École de Technologie Supérieure of Montreal | Boutin J.,IRSST
Journal of the Acoustical Society of America | Year: 2013

The axisymmetric hypothesis of the earplug-ear canal system geometry is commonly used. The validity of this hypothesis is investigated numerically in the case of a simplified configuration where the system is embedded in a rigid baffle and for fixed boundary conditions on the earplug lateral walls. This investigation is discussed for both individual and averaged insertion loss predictions of molded silicon earplugs. The insertion losses of 15 earplug-ear canal systems with realistic geometries are calculated using three-dimensional (3D) finite element models and compared with the insertion losses provided by two-dimensional equivalent axisymmetric finite element models using 6 different geometry reconstruction methods [all the models are solved using COMSOL Multiphysics (COMSOL®, Sweden)]. These methods are then compared in order to find the most reliable ones in terms of insertion loss predictions in this simplified configuration. Two methods have emerged: The usage of a variable cross section (with the same area values as the 3D case) or the usage of a constant cross section (with the same length and volume as the 3D case). © 2013 Acoustical Society of America.

Ma S.,Shandong University | Boukas E.-K.,Ecole Polytechnique de Montréal | Chinniah Y.,IRSST
International Journal of Robust and Nonlinear Control | Year: 2010

The stochastic stability and stochastic stabilization of time-varying delay discrete-time singular Markov jump systems are discussed. For full and partial knowledge of transition probabilities cases, delay-dependent linear matrix inequalities (LMIs) conditions for the systems to be regular, causal and stochastically stable are given. Sufficient conditions are proposed for the existence of state feedback controller in terms of LMIs. Finally, two numerical examples to illustrate the effectiveness of the method are given. © 2009 John Wiley & Sons, Ltd.

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