Acoustic metamaterials: noise control, Willis coupling and anomalous reflection

Anton Melnikov (Fraunhofer Institute for Photonic Microsystems IPMS) 

'Acoustic metamaterials: noise control, Willis coupling and anomalous reflection'

Abstract: Acoustic metamaterials are structures with exotic acoustic properties, with promising applications in noise mitigation, acoustic beam steering, focusing, and impedance matching. In recent years, many different designs have been proposed and investigated, whereas, not all of them are usable in practice due to expensive manufacturing, impedance mismatch, or thermos viscous losses. However, a simple c-shape meta-atom can overcome most of the issues and allows designing efficient acoustic metamaterials. In the first part of the talk, an acoustic metamaterial capsule for noise control based on a c-shape meta-atom is presented including numerical and experimental results. The second part deals with Willis coupling of acoustic scatterers, an acoustic analogy of bianisotropy. Here it is illustrated how Willis coupling can be tailored between zero and its maximum bound using c-shape meta-atoms. Furthermore, this part includes experimental results demonstrating Willis coupling magnitude of 90% of the limit given by the conservation of energy. Finally, the current progress on designing acoustic metagratings with high efficiency anomalous reflection using c-shape meta-atoms is reported.