Bending a periodically layered structure for transformation acoustics

Anisotropic acoustic metamaterials have been proved very useful for their high potential in guiding and manipulating sound energy. In this letter, we further develop the idea by using periodically layered structures for transformational acoustics. Such a simple scheme periodically inserts identically bent solid plates in a background fluid. It forms a metamaterial with high refractive index normal to the curved plates and an index near to one along the plates. We show that the periodically layered structure, combined with transformation approach, can be cut into particular device shapes for acoustic cloaking and illusion.