Acoustic Cloaking via Homogenization
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Acoustic cloaking is the mechanism representing the ideal acoustic stealth. We introduce and discuss the acoustic cloak, a material shell that renders an object acoustically ‘invisible’ thanks to its presence surrounding the object. It has been shown that cloaking shells require very complex parameters to be realized. This complexity comes from the fact that their acoustic parameters must be anisotropic, inhomogeneous and divergent near the cloaked object. This chapter explains how to engineer artificial structures, which have been called acoustic metamaterials or metafluids, that respond dynamically as anisotropic and inhomogeneous materials. The metafluids are made from arrays of isotropic and homogeneous elastic cylinders or by metallic plates cylindrically corrugated. We also propose solutions to remove the divergences appearing in the design of cloaking shells. It is therefore predicted that, although difficult to realize, cloaking shells are not impossible by using metafluids based on the homogenization of periodic structures.
KeywordsBulk Modulus Sound Speed Acoustic Parameter Filling Fraction Artificial Structure
The authors thank partial financial support by the US Office of Naval Research (Grant N000140910554) and by the Spanish Ministerio de Ciencia e Innovación (Grants TEC2010-19751 and CSD2009-0066 (CONSOLIDER program). D.T. also acknowledges the contract provided by the program Campus de Excelencia Internacional 2010 UPV.
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