Acoustic metamaterial for low frequency sound absorption in linear and nonlinear regimes

Brooke, DC; Umnova, O; Leclaire, P; Dupont, T

Abstract

Acoustic metamaterial absorbers have been built and tested with
focus on low frequency airborne sound absorption in linear and nonlinear
regimes. The absorbers are made up of a series of piled up flat cavities,
separated by thin walls and traversed by a perforation at their centre. A
model for absorber effective properties is developed and compared with
experimental data. The model is used to derive simple formulae for the
frequency and the peak value of the absorption coefficient at the lowest
frequency resonance, depending on the geometrical parameters of the
structure. Different absorbers have been built with several cavity
thicknesses to allow comprehensive comparisons with the model. Nonlinear
properties of the absorbers are investigated experimentally using sine
wave excitation around the resonance frequency with the amplitude of the
incident wave up to 250 Pa. Flow resistivity measurements at low flow
rates show that the periodic set of cavities does not modify resistivity
significantly when compared to a simple perforated cylinder with same
thickness. As flow rate increases, the flow resistivity grows linearly
according to Forchheimer's law and has a significant dependence on the
absorber thickness. A numerical model is developed accounting for the
linear growth of flow resistivity with particle velocity amplitude in the
central perforation and compared with the measurements at high amplitudes
of the incident wave.

• Journal Article Type: Article
• Acceptance Date: Jul 14, 2020
• Online Publication Date: Jul 16, 2020
• Publication Date: Oct 27, 2020
• Deposit Date: Jul 29, 2020
• Publicly Available Date: Aug 6, 2020
• Journal: Journal of Sound and Vibration
• Print ISSN: 0022-460X
• Publisher: Elsevier
• Volume: 485
• Pages: 115585
• DOI: https://doi.org/10.1016/j.jsv.2020.115585
• Publisher URL: https://doi.org/10.1016/j.jsv.2020.115585
• Related Public URLs: https://www.journals.elsevier.com/journal-of-sound-and-vibration/