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Sound Absorbing materials : modelling

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Full-Text Articles in Mechanical Engineering

Sound Absorption Properties Of Functionally Graded Polyurethane Foams, Olivier Doutres Ph.D., Noureddine Atalla Pr. Aug 2012

Sound Absorption Properties Of Functionally Graded Polyurethane Foams, Olivier Doutres Ph.D., Noureddine Atalla Pr.

Olivier Doutres Ph.D.

Noise control over a wide frequency band is an increasingly important design criterion in the building and transport industries. Examples of well known broadband passive concepts for optimal sound absorption are multi-layering with graded properties across the thickness and optimization of the material shape (e.g., wedges). However, for typical applications, the material thickness is limited and shaping or use of different material costly. Thus, there is growing interest for developing acoustical materials having microstructure properties gradient at the micro- or meso-scale; also known as Functionally Graded Materials (FGM). Even if sophisticated models are available to predict the acoustic behavior ...


Optimization Of The Acoustic Performance Of Polyimide Foams, Olivier Doutres, Noureddine Atalla, Rebecca Wulliman, Shari Ferguson, Steve Bailey Jul 2011

Optimization Of The Acoustic Performance Of Polyimide Foams, Olivier Doutres, Noureddine Atalla, Rebecca Wulliman, Shari Ferguson, Steve Bailey

Olivier Doutres Ph.D.

Due to their low weight, high fire resistance and good mechanical strength, SOLIMIDE® Polyimide foams are good candidates for sound packages in aerospace sound transmission applications. However, their high resistance to airflow limits the sound absorption efficiency inside a double wall structure and thus the sound transmission loss of the structure. The paper discusses two concepts to improve the transmission efficiency of such materials for double wall applications: (i) improving its sound absorption behavior by removing mechanically or chemically the cell membranes and thus decreasing both the flow resistance and tortuosity, (ii) coupling the Polyimide foams to screens (porous or ...


A Practical Impedance Tube Method To Estimate The Normal Incidence Sound Transmission Loss Of Double Wall Structure, Olivier Doutres, Noureddine Atalla Jul 2011

A Practical Impedance Tube Method To Estimate The Normal Incidence Sound Transmission Loss Of Double Wall Structure, Olivier Doutres, Noureddine Atalla

Olivier Doutres Ph.D.

The objective of this paper is to propose a practical impedance tube method to optimize the sound transmission loss of double wall structure by concentrating on the sound package placed inside the structure. In a previous work, the authors derived an expression that breaks down the transmission loss of a double wall structure containing a sound absorbing blanket separated from the panels by air layers in terms of three main contributions; (i) sound transmission loss of the panels, (ii) sound transmission loss of the blanket and (iii) sound absorption due to multiple reflections inside the cavity. The sound transmission loss ...


Optimisation Acoustique De Paroi Par Algorithme Génétique Et Influence De L’Habillage Par Une Couche Poreuse, Nicolas Dauchez, Olivier Doutres, Jean-Michel Genevaux, Jean-Christophe Le Roux Apr 2010

Optimisation Acoustique De Paroi Par Algorithme Génétique Et Influence De L’Habillage Par Une Couche Poreuse, Nicolas Dauchez, Olivier Doutres, Jean-Michel Genevaux, Jean-Christophe Le Roux

Olivier Doutres Ph.D.

L’amélioration du confort acoustique dans les habitacles passe en particulier par l’optimisation de la transparence acoustique de parois simple ou double au moyen de matériaux viscoélastiques et poreux. Une méthode d’optimisation de paroi basée sur un algorithme génétique couplé à un calcul par matrices de transfert est présentée. Cette technique permet une exploitation efficace des itérations précédentes sans coût de calcul supplémentaire. Les résultats obtenus pour une simple et une double paroi sont analysés. Dans un deuxième temps, l’influence d’un habillage poreux est présenté en fonction de la nature du squelette : mousse polymère ou fibreux ...


Validity Of The One-Dimensional Limp Model For Porous Media, Olivier Doutres, Nicolas Dauchez, Jean-Michel Génevaux, Olivier Dazel Dec 2007

Validity Of The One-Dimensional Limp Model For Porous Media, Olivier Doutres, Nicolas Dauchez, Jean-Michel Génevaux, Olivier Dazel

Olivier Doutres Ph.D.

A straightforward criterion for determining the validity of the limp model validity for porous materials is addressed here. The limp model is an “equivalent fluid” model which gives a better description of porous behavior than the well known “rigid frame” model. It is derived from the poroelastic Biot model, assuming that the frame has no bulk stiffness. A criterion is proposed for identifying the porous materials for which the limp model can be used. It relies on a new parameter, the Frame Stiffness Influence FSI, based on porous material properties. The critical values of FSI under which the limp model ...


Modelling Of The Acoustic Radiation Of A Structure Covered By A Porous Layer, Olivier Doutres, Nicolas Dauchez Apr 2005

Modelling Of The Acoustic Radiation Of A Structure Covered By A Porous Layer, Olivier Doutres, Nicolas Dauchez

Olivier Doutres Ph.D.

In many applications, porous materials such as polymers foams are attached to a structure subjected to vibration. This allows to diminish vibration by increasing structural damping or to reduce noise level in cavities by sound absorption. The radiation efficiency of the coupled system is studied. An analytical model has been carried out, separating the acoustical and vibratory behaviors: - The vibratory analysis is based on a dynamic study of an equivalent plate of the coupled system. In this case the porous layer is considered as a viscoelastic layer. - In the acoustical analysis, a surface impedance is applied on this equivalent plate ...