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      Dark acoustic metamaterials as super absorbers for low-frequency sound.

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          Abstract

          The attenuation of low-frequency sound has been a challenging task because the intrinsic dissipation of materials is inherently weak in this regime. Here we present a thin-film acoustic metamaterial, comprising an elastic membrane decorated with asymmetric rigid platelets that aims to totally absorb low-frequency airborne sound at selective resonance frequencies ranging from 100-1,000 Hz. Our samples can reach almost unity absorption at frequencies where the relevant sound wavelength in air is three orders of magnitude larger than the membrane thickness. At resonances, the flapping motion of the rigid platelets leads naturally to large elastic curvature energy density at their perimeter regions. As the flapping motions couple only minimally to the radiation modes, the overall energy density in the membrane can be two-to-three orders of magnitude larger than the incident wave energy density at low frequencies, forming in essence an open cavity.

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          Author and article information

          Journal
          Nat Commun
          Nature communications
          Springer Science and Business Media LLC
          2041-1723
          2041-1723
          Mar 27 2012
          : 3
          Affiliations
          [1 ] Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.
          Article
          ncomms1758
          10.1038/ncomms1758
          22453829
          b305eb58-ce44-4802-ac58-1a28e403194c
          History

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