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Conference_programme: 1.1 - Acoustic and Elastic Metamaterials

Lecture: Metafoams - mass enriched poroelastic material with exceptional attenuation performance

Author(s): Lewinska Miroslawa, Van Dommelen Johannes, Kouznetsova Varvara, Geers Marc

In our fast-developing industrial world there is a strong need for noise insulation which poses a challenging research. For sound absorption purposes, acoustic foams are commonly used, since the wave energy is effectively dissipated through the visco-thermal effects occurring within the pores. However, the performance of acoustic foams at low frequencies is rather limited. On the other hand, locally resonant acoustic metamaterials is another class of materials which can be used for acoustic/elastic wave attenuation. In this case, due to the resonances at the microstructural scale, so-called band gaps are formed [1], i.e. frequency ranges where no wave propagation is allowed. In terms of low frequency attenuation, locally resonant acoustic metamaterials seem to be particularly promising because the operating frequency can be easily tuned by an appropriate material/geometrical design. \nThe combination of the two effects, aiming at a broader attenuation frequency range is being actively researched, nevertheless, in most of the works resonators of a macroscale size are embedded in microporous foam-like material [2]. In this contribution, a poroelastic material enriched with resonating masses at the pore scale is considered. A FEM based numerical transmission set-up, which mimics the standard impedance tube test, is used to assess its performance. A great attention is given to the accurate description of solid and fluid domains as well as to the fluid-structure interaction. Preliminary results of transmission spectra show that the design with resonators performs remarkably better for low frequencies, compared with the design without the masses (the traditional foams) and that viscothermal effects in the fluid are indispensable for the improvement of the attenuation.\nAcknowledgment: The research leading to these results has received funding from the European Research Council under the European Union’s Seventh Framework Programme (FP7/2007-2013) / ERC grant agreement no [339392].\n[1] LewiƄska, M. A., et al. (2017). The attenuation performance of locally resonant acoustic metamaterials based on generalised viscoelastic modelling. Int. Jnl. Sol. Struct., 126, 163-174. \n[2] Doutres, O., et al. (2015). Transfer matrix modeling and experimental validation of cellular porous material with resonant inclusions. J. Acoust. Soc. Am., 137(6), 3502-3513\n

Corresponding author

Name: Ms Miroslawa Lewinska

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Country: Netherlands