Low frequency sound absorption in porous material with periodically distributed dead-end pores

Invited paper

Philippe Leclaire

DRIVE - ISAT - Université de Bourgogne

Tuesday 2 june, 2015, 09:20 - 09:40

0.7 Lisbon (47)

A theoretical and numerical study of the sound propagation in air-saturated porous media with straight pores bearing lateral cavities (dead-ends) is proposed. The straight pores can be considered as the main “Biot pores”. The lateral cavities are located at “nodes” periodically spaced along each "Biot pore" axis. 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 viscothermal losses in the main pores as well as their perforation rate. The presence of long or short dead-ends significantly alters the acoustical properties of the material. These depend strongly on the geometry (diameter and length) of the dead-ends, on their number per node and on the periodicity along the propagation axis. These effects are primarily due to low sound velocity in the main pores and on thermal losses occurring in the lateral cavities. The model predictions are compared with experimental results and examples of material design featuring periodically distributed dead-end pores are proposed.

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