High-quality acoustic cavities based on radial sonic crystals.

Radial sonic crystals are radially inhomogeneous systems that present a dispersion relation similar to one dimensional sonic crystals, with the peculiarity of having low-frequency band gaps. These structures are here employed to design high-quality circularly symmetric acoustic cavities. The presence of band gaps in their dispersion relation allows to localize sound in the cavity centers, leading to strong resonances whose frequency depends on the symmetry of the field. Therefore, it is possible to design cavities with monopolar, dipolar, quadrupolar, etc., symmetry. A proposal for its physical realization is also described, showing that radial sonic crystals are possible to build by using the concept of acoustic metamaterials. [Work supported by MCIIN of Spain and ONR.]