0000000000893844
AUTHOR
P. Leclaire
Experimental investigation of holes interaction effect on the sound absorption coefficient of micro-perforated panels under high and medium sound levels
Abstract This paper experimentally investigates the holes interaction effect on the sound absorption coefficient of micro-perforated panels under high and medium sound levels. The theoretical formulations are based on a semi-empirical approach and the use of Fok’s function to model the acoustic surface impedance. For the high sound level regime, an empirical power law involving three coefficients is adapted. It is shown theoretically and experimentally that these coefficients can lead to optimized absorption performance and particularly, a formula relating the critical Reynolds number (Reynolds number value after which the absorption coefficient decreases with the increase of sound level) a…
Acoustics of porous materials with partially opened porosity
International audience; A theoretical and experimental study of the acoustic properties of porous materials containing dead-end (or partially opened) porosity was recently proposed by Dupont et al. The present article provides a description of partially opened porosity systems and their numerous potential applications in the general context of the study of porous materials, the classical models describing them, and the characterization techniques. It is shown that the dead-end pore effect can be treated independently and that the description of this effect can be associated with any acoustic model of porous media. Different theoretical developments describing the dead-end porosity effect ar…
Acoustical properties of air-saturated porous material with periodically distributed dead-end pores
International audience; A theoretical and numerical study of the sound propagation in air-saturated porous media with straight main pores bearing lateral cavities (dead-ends) is presented. The lateral cavities are located at " nodes " periodically spaced along each main pore. The effect of periodicity in the distribution of the lateral cavities is studied, and the low frequency limit valid for the closely spaced dead-ends is considered separately. It is shown that the absorption coefficient and transmission loss are influenced by the viscous and thermal losses in the main pores as well as their perforation rate. The presence of long or short dead-ends significantly alters the acoustical pro…
Low Frequency and Nonlinear Acoustical Behaviour of Plates with Perforations Bearing Periodically Spaced Flat Resonators
International audience
Advanced dispersion measurement techniques for the characterization of the mechanical properties of poro-visco-elastic materials
Dispersion measurement techniques are normally used to determine the mechanical properties of poro-visco-elastic materials, such as their shear modulus. However, dispersion measurements of poro-visco-elastic materials are not easy and the experimentally accessible frequency range in which the modes of propagation are detectable is limited to the lower frequency range, typically up to about 1500 Hz. In this article an advanced measurement technique is discussed to perform the dispersion measurement, allowing to capture reliable measurement data up to higher frequencies and for higher order modes of propagation. A typical measurement result using the proposed approach is shown and the results…
Etude acoustique des mousses métalliques bicouches avec interface à gradient de propriétés
International audience
Mechanical, thermal and acoustical characterizations of an insulating bio-based composite made from sunflower stalks particles and chitosan
International audience; This study has for objective the determination of thermal, mechanical and acoustical properties of insulating bio-based composite made with chitosan and sunflower's stalks particles. An experimental design was established to find the size grading of particles, the ratio chitosan/sunflower particles and the stress of compaction influencing the thermal and mechanical properties. Composites with a thermal conductivity $(\kappa)$ of 0.056 W/m/K, a maximum stress $(\sigma_{\text{max}})$ of 2 MPa and an acoustic coefficient of absorption $(\alpha)$ of 0.2 were obtained with a ratio of chitosan of 4.3% (w/w) and a size grading of particles higher to 3 mm. These mechanical a…
Transfer matrix method applied to the parallel assembly of sound absorbing materials
International audience; The transfer matrix method (TMM) is used conventionally to predict the acoustic properties of laterally infinite homogeneous layers assembled in series to form a multilayer. In this work, a parallel assembly process of transfer matrices is used to model heterogeneous materials such as patchworks, acoustic mosaics, or a collection of acoustic elements in parallel. In this method, it is assumed that each parallel element can be modeled by a 2 × 2 transfer matrix, and no diffusion exists between elements. The resulting transfer matrix of the parallel assembly is also a 2 × 2 matrix that can be assembled in series with the classical TMM. The method is validated by compar…