Phys.org March 7, 2019
Based on the premise that metamaterial needs to be shaped in such a way that it sends incoming sounds back to where they came from, researchers at Boston University calculated the dimensions and specifications that the metamaterial would need to have in order to interfere with the transmitted sound waves. Using the calculation they created a structure made of plastic that could silence sound from a loudspeaker. In tests they found that 94 percent of the sound emanating from the loudspeaker was imperceptible to the human ear. The shape of acoustic-silencing metamaterials is also completely customizable. The research has applications in smart sound barriers, fan or engine noise reduction in factory settings etc…read more. TECHNICAL ARTICLE
Inside the outer ring, a helical pattern interferes with sounds, blocking them from transmitting through the open center while preserving air’s ability to flow through. Credit: Cydney Scott for Boston University