Leclaire P, Umnova O, Dupont T, Panneton R
DRIVE-ISAT, Université de Bourgogne, 49 Rue Mademoiselle Bourgeois, 58027 Nevers Cedex, France.
Acoustics Research Centre, University of Salford, Salford M5 4WT, United Kingdom.
J Acoust Soc Am. 2015 Apr;137(4):1772-82. doi: 10.1121/1.4916712.
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 properties of the material and can increase significantly the absorption at low frequencies (a few hundred hertz). 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 speed in the main pores and to thermal losses in the dead-end pores. The model predictions are compared with experimental results. Possible designs of materials of a few cm thicknesses displaying enhanced low frequency absorption at a few hundred hertz are proposed.
本文对具有带有横向腔体（盲端）的直主孔的空气饱和多孔介质中的声传播进行了理论和数值研究。横向腔体位于沿每个主孔周期性间隔分布的“节点”处。研究了横向腔体分布的周期性影响，并分别考虑了对紧密间隔的盲端有效的低频极限情况。结果表明，吸收系数和传输损耗受主孔中的粘性和热损耗及其穿孔率的影响。长盲端或短盲端的存在会显著改变材料的声学特性，并能在低频（几百赫兹）下显著增加吸收。这些特性强烈依赖于盲端的几何形状（直径和长度）、每个节点处的数量以及沿传播轴的周期性。这些效应主要归因于主孔中的低声速和盲端孔中的热损耗。将模型预测结果与实验结果进行了比较。提出了几种厚度为几厘米、在几百赫兹处具有增强低频吸收的材料的可能设计方案。
