Azbaid et al EuroNoise 2015.pdf (574.98 kB)

Gradient metamaterial layers as impedance matching devices for efficient sound absorption

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conference contribution
posted on 19.08.2015, 14:15 by Abdelhalim Azbaid El Ouahabi, Victor V. Krylov, Daniel O'Boy
The performance of acoustic absorbers can be improved by providing a smooth transition from the impedance of air to the impedance of the absorbing material in question. In the present work, such a smooth transition is materialised via application of gradient index metamaterial layers formed by quasi-periodic arrays of solid cylinders (tubes) with their external diameters gradually increasing from the external row of tubes facing the open air towards the internal row facing an absorbing porous layer. If acoustic wavelengths are much larger than the periodicity of the array, such a structure provides a gradual increase in the acoustic impedance towards the internal row of cylinders. This allows the developer to achieve an almost perfect impedance matching between the air and porous absorbing materials, such as foams, sponges, etc. Measurements of sound reflection coefficients from different absorbing materials combined with matching metamaterial layers formed by the arrays of brass tubes have been carried out in an anechoic chamber at the frequency range of 500-3000 Hz. The results show that the presence of matching metamaterial layers brings substantial reduction in the sound reflection coefficients, thus increasing the efficiency of sound absorption.

Funding

This research has been supported by EPSRC grant EP/K038214/1.

History

School

  • Aeronautical, Automotive, Chemical and Materials Engineering

Department

  • Aeronautical and Automotive Engineering

Published in

EuroNoise 2015 Proceedings of the 10th European Congress and Exposition on Noise Control Engineering, 'EuroNoise 2015'

Pages

989 - 994

Citation

AZBAID EL OUAHABI, A., KRYLOV, V.V. and O'BOY, D.J., 2015. Gradient metamaterial layers as impedance matching devices for efficient sound absorption. IN: Glorieux, C. (ed.). Proceedings of the 10th European Congress and Exposition on Noise Control Engineering, EuroNoise 2015, Maastricht, The Netherlands, 31st May - 3rd June 2015, pp.989-994.

Publisher

European Acoustics Association

Version

VoR (Version of Record)

Publisher statement

This work is made available according to the conditions of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) licence. Full details of this licence are available at: https://creativecommons.org/licenses/by-nc-nd/4.0/

Publication date

2015

Notes

This paper is also freely available online at: http://www.conforg.fr/euronoise2015/output_directory/data/articles/000502.pdf.

ISSN

2226-5147

Language

en

Location

Maastricht, The Netherlands

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