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Wednesday, July 10 • 17:10 - 17:30
ACOUSTIC METAMATERIAL DESIGN FOR LOW FREQUENCY SOUND ABSORPTION IN LINEAR AND NONLINEAR REGIMES

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An acoustic metamaterial absorber comprised of periodically distributed cavities has been built and tested with focus on low frequency sound absorption in linear and nonlinear regimes. The absorber is made up of a series of piled up pancake-like flat cavities saturated by air, separated by thin walls and traversed by a perforation at their centre. Viscous and thermal boundary layer thicknesses near the solid walls are small compared to microstructure dimensions, however the losses are non-negligible. This results in energy attenuation and abrupt wave speed reduction in the central perforation or main pore. A model for absorber effective properties is developed and compared with experimental data. The model is used to predict the frequency and the peak value of the absorption coefficient at resonance, depending on the geometrical parameters of the structure. Optimum design of the pancake structure enables to obtain the high absorption at the desired frequency. The central pore radius and the size of the cavities are shown to impact the frequency of the absorption peak. Nonlinear properties of the absorber are investigated using sine wave excitation around the resonance, which allows to obtain variations of the absorption coefficient with the amplitude of the incident wave. The flow resistivity is shown to be of great influence on the linear and nonlinear behaviour of the resonator. Flow resistivity measurements on a pancake resonator at low and higher flow rates show that the periodic set of cavities does not modify significantly the flow resistivity when compared to a simple perforated structure with same thickness.

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 17:10 - 17:30 EDT
St-Laurent 5
  T08 Mat. for noise & vibr. cntrl., SS01 Pasv snd absorb & insul mtrl