Abstract
It has been found that when a layer of activated carbon partially fills the space behind a finite, edge-constrained, tensioned impermeable membrane, the absorption peaks due to the modal response of the membrane can be significantly enhanced in the low frequency range. In the present work, the modeling aspects of the latter work have been extended to allow the membrane to be both tensioned and flexurally-stiff, and further, to be micro-perforated, thus expanding the treatment design space. Secondly, the particle layer behind the membrane is modeled by using a two-dimensional finite difference implementation of the Biot poro-elastic theory which then accounts for the interaction of the particle layer and walls that contain it: i.e., the solid phase of the particle stack itself is allowed to exhibit modal behavior in the radial direction. The interaction of the membrane nearfield and the particle stack, which creates a nearfield damping effect, is also fully captured. Finally, the model accounts for the hierarchical porosity of activated carbon. The model has been verified by comparison with measurements and it has been found that strikingly high levels of low frequency absorption can be realized by appropriate optimization of the membrane and particle stack properties and geometry.
Keywords
Sound absorption, Microperforated panels, Activated Carbon, Nearfield damping, Tensioned membrane, Granule stacks
Subject
Acoustics and Noise Control
Date of this Version
5-13-2024
Comments
Zhuang Mo, Guochenhao Song, Huawei Yang, Tongyang Shi and J. Stuart Bolton, “The acoustics of absorbers comprising a flexible perforated membrane backed by a stack of granular material,” 186th meeting of the Acoustical Society of America, Ottawa, ON, May 2024. Paper 1aCA1, Session: Computational Methods for Acoustic Absorption in Materials ((Invited by Shung H. Sung, D. Keith Wilson and Kuangcheng Wu). Abstract published in the Journal of the Acoustical Society of America.