Eurekalert  May 10, 2018
Researchers at Pennsylvania State University have designed material to redirect approaching waves around an object without scattering the wave energy, concealing the object from the sound waves. They designed a 3-foot-tall pyramid out of perforated steel plates and placed the structure on the floor of a large underwater research tank. Inside the tank, a source hydrophone produced acoustic waves between 7,000 Hz and 12,000 Hz, several receiver hydrophones around the tank monitoring reflected acoustic waves. The wave reflected from the metamaterial matched the phase of the reflected wave from the surface demonstrating that the material could make an object appear invisible to underwater instruments like sonar…read more.
This image is a Profile picture of the assembled perforated plate ground cloak. CREDIT: Peter Kerrian