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Microstructures for lowering the quarter wavelength resonance frequency of a hard-backed rigid-porous layer

Attenborough, Keith (2018). Microstructures for lowering the quarter wavelength resonance frequency of a hard-backed rigid-porous layer. Applied Acoustics, 130 pp. 188–194.

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The frequency of the quarter wavelength resonance in the sound absorption spectra due to a thin hard-backed rigid-porous layer can be influenced by the design of its microstructure as well as its thickness. Microstructures considered include parallel arrays of identical cylindrical, slit-like or rectangular pores with deep sub-wavelength cross sections inclined to the surface normal, cylindrical annular pores, slits with log-normal width distributions, slits with cross sections that vary in a sinusoidal manner and slits with two distinct widths (dual porosity). Formulae that predict the bulk acoustical properties due to these microstructures are presented and used to explore the extent to which specific microstructures could be used separately or in combination to improve low-frequency absorption. Predicted normal incidence absorption coefficient spectra are compared using microstructural dimensions that would be feasible for 3D printing. The most effective microstructures are predicted to be slits with sinusoidally-varying widths, or with two distinct widths, inclined to the surface normal at 70°. The quarter wavelength layer resonances predicted in absorption coefficient spectra using these microstructures are comparable with those predicted for layers of the same thickness and bulk porosity having cylindrical pores with dead-end branches.

Item Type: Journal Item
Copyright Holders: 2017 Elsevier
ISSN: 0003-682X
Project Funding Details:
Funded Project NameProject IDFunding Body
COST network DENORMSCA 15125EC
Keywords: porous absorber; slit microstructures; quarter-wavelength resonance
Academic Unit/School: Faculty of Science, Technology, Engineering and Mathematics (STEM) > Engineering and Innovation
Faculty of Science, Technology, Engineering and Mathematics (STEM)
Item ID: 51320
Depositing User: Keith Attenborough
Date Deposited: 05 Oct 2017 08:24
Last Modified: 13 May 2019 04:22
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