How reproducible is the acoustical characterization of porous media?

There is a considerable number of research publications on the characterization of porous media that is carried out in accordance with ISO 10534-2 (International Standards Organization, Geneva, Switzerland, 2001) and/or ISO 9053 (International Standards Organization, Geneva, Switzerland, 1991). According to the Web of Science(TM) (last accessed 22 September 2016) there were 339 publications in the Journal of the Acoustical Society of America alone which deal with the acoustics of porous media. However, the reproducibility of these characterization procedures is not well understood. This paper deals with the reproducibility of some standard characterization procedures for acoustic porous materials. The paper is an extension of the work published by Horoshenkov, Khan, Bécot, Jaouen, Sgard, Renault, Amirouche, Pompoli, Prodi, Bonfiglio, Pispola, Asdrubali, Hübelt, Atalla, Amédin, Lauriks, and Boeckx [J. Acoust. Soc. Am. 122(1), 345-353 (2007)]. In this paper, independent laboratory measurements were performed on the same material specimens so that the naturally occurring inhomogeneity in materials was controlled. It also presented the reproducibility data for the characteristic impedance, complex wavenumber, and for some related pore structure properties. This work can be helpful to better understand the tolerances of these material characterization procedures so improvements can be developed to reduce experimental errors and improve the reproducibility between laboratories

How reproducible are methods to measure the dynamic viscoelastic properties of poroelastic media?

There is a considerable number of research publications on the acoustical properties of porous media with an elastic frame. A simple search through the Web of Science™ (last accessed 21 March 2018) suggests that there are at least 819 publications which deal with the acoustics of poroelastic media. A majority of these researches require accurate knowledge of the elastic properties over a broad frequency range. However, the accuracy of the measurement of the dynamic elastic properties of poroelastic media has been a contentious issue. The novelty of this paper is that it studies the reproducibility of some popular experimental methods which are used routinely to measure the key elastic properties such as the dynamic Young's modulus, loss factor and Poisson ratio of poroelastic media. In this paper, fourteen independent sets of laboratory measurements were performed on specimens of the same porous materials. The results from these measurements suggest that the reproducibility of this type of experimental method is poor. This work can be helpful to suggest improvements which can be developed to harmonize the way the elastic properties of poroelastic media are measured worldwide

Effets d'un fluide en écoulement uniforme sur le comportement vibro-acoustique d'une plaque bafflée couplée à une cavité rectangulaire

The purpose of this work is to develop a general formulation to deal with the vibro-acoustic behavior of a baffled plate, immersed on one side in a mean flow and coupled on the other side to a rectangular cavity with arbitrary wall impedances. The plate is excited by a plane wave convected by the mean flow. The formulation is based on a finite element method for the calculation of the transverse vibrations of the plate and the acoustic field inside the cavity. The external fluid loading is accounted for through the extended Kirchoff-Helmoltz integral equation and the radiation impedance of the plate in the external fluid is computed with a boundary element method. The mean flow effects on the transmission loss of the plate are discussed

Rayonnement acoustique de structures non bafflées

If the simulation of the radiated field of a baffled plane structure has been deeply studied, the unbaffled case, although more realistic, has retained little attention. The proposed works tend to simulate, by an analytical approach, the radiation of a plane unbaffled structure of finite dimensions and general elastic type of boundary conditions. This approach is based on an integral method coupled with a Ritz approach for the calculus of the displacement field of the structure. The power is evaluated through the pressure jump across the plate. Translation and rotational springs create varying boundary conditions. A good comparison is found with a numerical approach (B.E.M.). Parametric studies showed the effect of the baffle. Precise measurements confirm the validity of the simulations

Biais anxieux de perception des risques

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