Camouflage devices with simplified material parameters based on conformal transformation acoustics

Owing to the recent fascinating advances in transformation acoustics, it is possible to design the distribution of refractive index of attractive devices that can manipulate acoustic waves in almost any manner. Furthermore, if the transformation is conformal, the resultant devices can be made with ordinary isotropic materials instead of exotic anisotropic metamaterials. In this paper, we use conformal transformation acoustics to design camouflage devices with layered homogeneous structures, which can acoustically generate illusions of objects. We demonstrate two devices: one is called shifter that makes an object appearing at different places from the actual location; another is called combiner that makes two objects at separated locations looking like only one object.