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Wednesday, July 10 • 11:30 - 11:50
EFFECT OF ELASTICITY AND STRUCTURAL RESONANCES ON THE ABSORPTION AND TRANSMISSION PROPERTIES OF MULTI-LAYER MICRO-PERFORATED PANELS

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Resonance absorbers made up of thin micro-perforated panels (MPPs) have shown to provide effective sound absorption and/or insulation performance at mid-frequencies. They can be made of lightweight and non-fibrous materials such as thin acryl glass or polymeric sheets, and find many applications in building infrastructures, transportation systems and noise abatement procedures. Combinations of multiple MPPs, panels and air cavities are known to provide enhanced absorption and transmission performance over bandwidths that can be broadened towards the low-frequency range, in particular those that create a positive gradient of the material's flow resistance. However, a large number of studies assume rigid MPPs of infinite lateral extent, which can be questionable when dealing in practice with micro-perforated limp sheets with prescribed boundary conditions along the edges. The current paper aims at investigating the effects of flexural vibrations on the absorption and transmission properties of multi-layer MPPs (ML-MPPs) in order to evaluate their influence on the absorptivity at low frequencies under normal incidence. The effects of elasticity on the absorptivity are first assessed on ML-MPPs of infinite lateral extent using a translation approach that incorporates the in-hole air-frame relative velocity inside the MPPs effective impedance. These effects are also evaluated from a modal matching formulation that has been extended to account for the MPPs flexural vibrations. It is shown that the elasticity enhances the absorptivity provided that the MPPs have a low surface density and do not already achieve optimal input resistance. Assuming finite-sized panels, the effects of the structural resonances on the absorptivity of ML-MPPs are predicted by a fully-coupled modal approach. Of interest is to assess how the panels volumetric resonances may produce excess dissipation at low frequencies.

Moderators
FA

francesco Asdrubali

Full Professor, Università Roma Tre - Department of Engineering
TD

Thomas Dupont

Associate Professor, École de Technologie Supérieure (ÉTS)
PL

Philippe Leclaire

Prof., ISAT - University of Burgundy
avatar for Raymond Panneton

Raymond Panneton

Ing., Ph.D., GAUS, Université de Sherbrooke
Raymond Panneton is a professor-researcher in the Department of Mechanical Engineering at the Université de Sherbrooke since 1998. His research program focuses on the modeling, characterization and optimization of porous acoustic media. More specifically, he explores the relationships... Read More →

Authors

Wednesday July 10, 2019 11:30 - 11:50 EDT
St-Laurent 5
  T08 Mat. for noise & vibr. cntrl., SS01 Pasv snd absorb & insul mtrl