Science Daily April 10, 2018
Using 3-D printers, an international team of researchers (USA – Duke University, Finland) fabricated a metamaterial made of a series of rows of hollow columns with a narrow opening cut down the middle of one side. The width of the channels between each row of columns and the size of the cavity inside each individual column controls how the sound is manipulated. The program is fed boundary conditions needed to dictate the outgoing and reflected waves’ behavior. They demonstrated redirecting a sound wave coming straight at the metamaterial to a sharp 60-degree outgoing angle with an efficiency of 96 percent. The metamaterials could be scaled to affect almost any wavelength of sound. They plan to transfer these ideas to the manipulation of sound waves in water for applications such as sonar, although there aren’t any ideas for applications in air…read more. Open Access TECHNICAL ARTICLE
This metamaterial surface has been engineered to perfectly and simultaneously control the transmission and reflection of incoming sound waves. Credit: Junfei Li