Acoustic omnidirectional superabsorber with arbitrary contour

Using transformation acoustics we have constructed an arbitrarily contoured acoustic omnidirectional superabsorber (AOSA) which consists of a guiding shell of negative-index metamaterial and a sound absorptive cavity. A square AOSA with anisotropic parameters and a circular AOSA with isotropic parameters are demonstrated. The consistent results by numerical full-wave simulation, analytic scattering-theory derivation, and sound ray tracing show that the AOSA can completely absorb the incident acoustic waves with arbitrary incident angle. For theoretically unlimited bandwidth, the absorption across section of the AOSA in a fixed geometric size can be made arbitrarily larger than the size of itself. Interesting applications of the proposed superabsorber such as ventilated sound insulation window are further discussed. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3690899]