Acoustic Cloaking

Introduction An acoustic cloak is a shell surrounding an object so that sound incident from any direction passes through and around the cloak, making the cloak and the object acoustically “invisible.” We do not experience acoustic cloaking because the materials required are exotic and, as far as we know, not found in nature. Yet there is no fundamental physical restriction on acoustic cloaking. Implementation is a matter of developing metamaterials with very unusual properties. Acoustic cloaking is in fact more likely to be achieved before its electromagnetic (EM) counterpart. he reason is that the cloaking material must have structure on sub-wavelength scales. Speciic examples will be explained below. Acoustic wavelengths are typically orders of magnitude larger than optical wavelengths, meters vs. microns, which makes the acoustic problem easier, in principle.