Groupe Dacoustique Of Luniversite Of Sherbrooke


Groupe Dacoustique Of Luniversite Of Sherbrooke


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Conte F.,Centrale Innovation | Roger M.,École Centrale Lyon | Moreau S.,Université de Sherbrooke | Moreau S.,Groupe Dacoustique Of Luniversite Of Sherbrooke | And 3 more authors.
17th AIAA/CEAS Aeroacoustics Conference 2011 (32nd AIAA Aeroacoustics Conference) | Year: 2011

Analytical modeling of the tonal noise radiated by a subsonic axial-flow fan placed in an air-cooling system is considered, instead of the more classical formulation neglecting installation effects. Two mechanisms are addressed separately, namely the noise associated with a stationary distorted inflow, and the potential-interaction noise due to downstream structural elements. For the first mechanism the distortion is determined from CFD computations and used as input data for the analytical calculation of the blade-loading harmonics. The tip-gap flow of the fan is investigated as the origin of a specific distortion. For the second mechanism, the distortion field is also modeled analytically. In both cases the radiation is considered in free field because the model is dedicated to unducted fans. The brake cooling fan of an aircraft landing gear is chosen as test case for the sake of illustration. © 2011 by the author(s).

Verron C.,McGill University | Verron C.,The Interdisciplinary Center | Gauthier P.-A.,The Interdisciplinary Center | Gauthier P.-A.,Groupe Dacoustique Of Luniversite Of Sherbrooke | And 4 more authors.
IEEE Transactions on Audio, Speech and Language Processing | Year: 2013

A method for spectral and spatial multichannel analysis/synthesis of interior aircraft sounds is presented. We propose two extensions of the classical sinusoids+noise model, adapted to multichannel stationary sounds. First, a spectral estimator is described, using average information across channels for spectral peak detection. Second, the residual modeling is extended to integrate two interchannel spatial cues (i.e., coherence and phase difference). This approach allows real-time synthesis and control of sounds spectral and spatial characteristics. It finds applications for multichannel aircraft sound reproduction, and more generally for musical and environmental sound synthesis. The ability of the model to reproduce multichannel aircraft sounds is assessed by a numerical simulation. © 2006-2012 IEEE.

Mosanenzadeh S.G.,University of Toronto | Naguib H.E.,University of Toronto | Park C.B.,University of Toronto | Atalla N.,Groupe Dacoustique Of Luniversite Of Sherbrooke
Journal of Applied Polymer Science | Year: 2014

In this study, a highly porous and interconnected foam structure was fabricated using compression molding combined with particulate-leaching technique. The foamed structures were fabricated with polylactide (PLA) and polyethylene glycol (PEG) with salt as the particulate. The pore size of the foam structure is controlled by the particulates size and higher interconnectivity is achieved by the co-continuous blending morphology of the PLA matrix with the water-soluble PEG. PLA is a fully bio-based thermoplastic polymer and is derived from renewable resources, such as cornstarch or sugarcanes. PEG is also fully biodegradable polymer produced from ethylene. Fabricated foams were characterized for cellular, acoustic, and mechanical properties. The acoustic performance of the foams was studied by measuring the normal incident absorption coefficient in accordance with the ASTM E1050 standard. The results show open porosity as high as 88% was achieved and the effect of water-soluble polymer on cellular properties and acoustic and mechanical performance of the foams was studied. As a result of the secondary porous structure formed into cell walls by water soluble polymer, the overall absorption of fabricated PLA foams was increased to above 90% while the average absorption of the foams remained unchanged. In addition, the resulting acoustic foams are benign and environmentally friendly. © 2013 Wiley Periodicals, Inc.

Winkler J.,University of Siegen | Winkler J.,Institute For Fluid Und Thermodynamik | Winkler J.,Boston University | Moreau S.,Université de Sherbrooke | And 3 more authors.
AIAA Journal | Year: 2012

In recent studies, trailing-edge blowing has been found to be a potential technique for broadband noise reduction in turbomachinery applications with rotor-stator arrangement. The primary idea involves injecting fluid into the wake of the rotor such that the wake becomes momentumless, and the turbulence structure is modified by the enhanced mixing process. This wake manipulation should lead to a reduced aeroacoustic response of the downstream stator vane with the modified turbulent wake of the rotor. This study investigates the trailing-edge blowing mechanism by numerical means in a simplified configuration. A large-eddy simulation of a single NACA 6512-63 airfoil at a low Mach number with trailing-edge blowing is undertaken to investigate the effect of blowing on wallpressure statistics of the blowing airfoil and also on its wake turbulence structure. The broadband self-noise and the wake-airfoil interaction noise are predicted from the simulation using Amiet's edge noise theories. It appears that two competing mechanisms exist: an increased airfoil self-noise for frequencies above 2 kHz due to the blowing jet interacting with the trailing edge and a reduction in wake-airfoil interaction noise for frequencies below 2 kHz through wake turbulence reduction. The predictions compare well to microphone measurements from wind-tunnel experiments. © 2011 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

Robin O.,Groupe Dacoustique Of Luniversite Of Sherbrooke | Chazot J.-D.,CNRS Roberval Laboratory (Mechanical Research Unit) | Boulandet R.,Groupe Dacoustique Of Luniversite Of Sherbrooke | Michau M.,Groupe Dacoustique Of Luniversite Of Sherbrooke | And 2 more authors.
Acta Acustica united with Acustica | Year: 2016

A technique to setup a simply supported rectangular plane panel for laboratory vibroacoustic tests is described and validated. For a given panel fixed to thin vertical supports, a dimensionless parameter is proposed to size these supports following a desired frequency precision compared to theoretical eigenfrequencies of a panel with such boundary conditions. A numerical study confirms the potential of this design parameter. Detailed instructions for assembling a panel with adequate thin vertical supports on a rigid frame are then given. Finally, three laboratory cases are described which illustrate possible experimental vibroacoustic applications using a panel assembled following previous guidelines. The design parameter viability is experimentally confirmed, and all obtained results depicted good agreement with analytical solutions and numerical predictions.

Ghaffari Mosanenzadeh S.,King's College | Doutres O.,Groupe Dacoustique Of Luniversite Of Sherbrooke | Naguib H.E.,King's College | Park C.B.,King's College | Atalla N.,Groupe Dacoustique Of Luniversite Of Sherbrooke
Applied Acoustics | Year: 2015

In order to understand the acoustic behavior of porous membranes, there is a need to further investigate the link between microstructure and macroscopic properties of such materials. This study presents the sound absorption properties of a novel bimodal foam structure made of polylactide (PLA) with an interconnected network of pores and micropores of very different characteristic sizes, fabricated utilizing the blend of PLA and polyethylene glycol (PEG) water soluble polymer. Fabricated foams are bio-based and have the advantage of resolving the environmental concerns raised by petrochemical based sound absorbers. The purpose of this study is to develop bio-based open cell structures as a practical solution to today's needs for noise control resolutions. Acoustic performance of the bimodal PLA foams is studied by measuring the normal incident absorption coefficient and the effect of bimodal structure is investigated in terms of acoustic properties (i.e., sound absorption) and non-acoustic properties associated to the Johnson-Champoux-Allard model (i.e., porosity, airflow resistivity, tortuosity, ...). Inverse method based on JCA model and impedance tube measurements for normal incident absorption coefficient was applied to estimate tortuosity and characteristic lengths. Results of inverse method are in good agreement with direct measurements of normal incident absorption coefficient. While tortuosity increases by increasing the polymer weight percent, it remains constant as the secondary porous structure extends in the porous medium. As the bimodal structure extends through the foam, both thermal and viscous characteristic lengths increase for different foam categories. © 2014 Elsevier Ltd. All rights reserved.

Robina O.,Groupe Dacoustique Of Luniversite Of Sherbrooke | Amedin C.K.,Groupe Dacoustique Of Luniversite Of Sherbrooke | Berry A.,Groupe Dacoustique Of Luniversite Of Sherbrooke | Atalla N.,Groupe Dacoustique Of Luniversite Of Sherbrooke | And 2 more authors.
INTER-NOISE 2015 - 44th International Congress and Exposition on Noise Control Engineering | Year: 2015

A method for estimating the sound absorption coefficient of a material under a synthesized Diffuse Acoustic Field was recently proposed, as an alternative to classical sound absorption measurements in reverberant rooms. Using sound field reproduction approaches and a synthetic array of acoustic monopoles facing the material, estimation of the sound absorption coefficient under a reproduced Diffuse Acoustic Field but in free-field conditions was shown to be feasible. The method was successfully tested on two samples of melamine foam of close thicknesses and areas. In this paper, the principle of the method will be first recalled. The effect of varying the reproduction array size on the calculated sound absorption coefficients is then studied. A comparative measurement between the suggested method and the reverberant room method on ceiling tiles is finally reported. © 2015 by ASME.

Gerard A.,Groupe Dacoustique Of Luniversite Of Sherbrooke | Besombes M.,CETIM | Berry A.,Groupe Dacoustique Of Luniversite Of Sherbrooke | Masson P.,Groupe Dacoustique Of Luniversite Of Sherbrooke | Moreau S.,Groupe Dacoustique Of Luniversite Of Sherbrooke
Noise Control Engineering Journal | Year: 2013

Tonal noise originates from non-uniform flow that causes circumferentially varying blade forces and gives rise to a considerably larger radiated dipolar sound at the blade passage frequency (BPF) and its harmonics. The approach presented in this paper adapts a tonal noise control method previously developed for axial fans to centrifugal fans using obstructions in the flow to destructively interfere with the primary non-uniform flow arising from stator/rotor interaction. The flow control obstruction is located such that the secondary radiated noise is of equal magnitude but opposite in phase compared to the primary noise. Experiments were carried out for a centrifugal fan test bench to validate the method for controlling BPF tonal noise by carefully positioning obstructions in a duct in the upstream flow. © 2013 Institute of Noise Control Engineering.

Alimonti L.,Groupe Dacoustique Of Luniversite Of Sherbrooke | Atalla N.,Groupe Dacoustique Of Luniversite Of Sherbrooke | Berry A.,Groupe Dacoustique Of Luniversite Of Sherbrooke | Sgard F.,IRSST
42nd International Congress and Exposition on Noise Control Engineering 2013, INTER-NOISE 2013: Noise Control for Quality of Life | Year: 2013

Modeling complex vibroacoustic systems including poroelastic materials using Finite Element (FE) based methods can be computationally expensive. For this reason, fast analytical approaches, such as the Tranfer Matrix Method (TMM), are often preferred to such sophisticated numerical techniques. However, analytical methodologies suffer from a lack of accuracy in the description of the geometry of the system. To alleviate this drawback, attempts have been made to couple a FE model of the elastic and acoustic domains with a TM model of the sound package. The authors recently proposed a hybrid methodology based on a Green's function formulation to account for sound packages in FE models. Although this hybrid methodology seems capable of capturing the physics better than classical approaches, the simplifications introduced by the analytical model can, in some cases, lead to an erroneous estimation of the vibroacoustic performance. In this work, the limitations of the methodology are assessed. A benchmark of typical vibroacoustic systems is presented to show the misbehavior of the hybrid model by a comparison with the FE solution. This lack of accuracy is due to the assumption of an infinite extent sound package inherent within the TMM. Copyright © (2013) by Austrian Noise Abatement Association (OAL).

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