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Wednesday, July 10 • 13:30 - 13:50
OPTIMISED MICRO-PERFORATED PANELS FOR BROADBAND ABSORPTIVITY

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The use of perforated and micro-perforated structures for applications with minimum weight penalties has been traditionally employed with good performance in the middle frequency range. In the search to improve performance at low frequencies, functionally-graded materials composed of layer of perforated panels with varying physical parameters are studied in this work. Several analytical formulations have been implemented and compared with other classical impedance translation methods. A modal matching formulation combined with Fourier-Floquet expansion has been selected in terms of accuracy and computational cost-efficiency to perform parametric studies carried out under normal incidence. Conclusions have been drawn concerning the dependency of the acoustic band gaps on the thicknesses of the fluid/solid layers, on the perforation ratio and on their variation within the structure. An optimisation procedure using the simulated annealing algorithm has considered a cost function for absorptivity of the system, which could provide simultaneously high absorption and low transmission. Frequencies have been identified at which one-sided critical coupling condition is achieved and for which the effective characteristic impedance matches that of the surrounding medium. To further enhance performance over a broader frequency range, a membrane has been added at the transmitting face of the partition. A comparison with other classical perforated or micro-perforated devices shows that, with a proper distribution of the parameters, the ultra-thin membrane is able to improve the blockage of the transmitted sound without the drawback of increasing the reflection in the frequency range of interest.

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 13:30 - 13:50 EDT
St-Laurent 5
  T08 Mat. for noise & vibr. cntrl., SS01 Pasv snd absorb & insul mtrl