Fig. 10
a–c are adapted from [16] and d–f are adapted from [75]
a The design of acoustic cloaking by Zhang et al. [16]. It consists of concentric layers with proper cavities and channels. b A unit cell of acoustic cloaking structure. The unit cell consists of a cavity with a large volume and four narrow channels as like as a shunt capacitor and serial inductors. c A measured pressure field plot at 64 kHz. The acoustic cloaking structure lies in the center of the water tank and the steel cylinder is positioned inside the structure. There is almost no scattering behind the structure, so that it shows the steel cylinder is well cloaked. d Scheme of physical structure designed (above) and a photograph of actual pyramid-shaped structure with perforated plastic plates (below). e Scheme of an experimental setup. There is a scanning microphone and A, B and C are specific points to be measured. f Instantaneous scattered pressure fields in each case. The case “Cloak” is well matched with “Ground” compared to “Object.” By arranging the pyramid-shaped structure, the inner space of the structure is recognized as empty one.