Anton Melnikov, Fraunhofer Institute for Photonic Microsystems IPMS. Microwave Seminar at The Department of Physics & Engineering, ITMO | 05/18/2020
Title: "Acoustic metamaterials: noise control, Willis coupling and anomalous reflection"
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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 metaatom 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.
00:00:00 Speaker presentation
00:01:06 Start of the talk
00:02:33 Introduction to acoustics
00:09:25 Introduction to acoustic waves
00:12:19 Acoustic metamaterials
00:15:16 Question from Alexey Slobozhanyuk about the unit cell manufacturing process.
00:15:50 Concepts for noise mitigation
00:20:39 C-shaped unit cell acoustic metagrating and metacapsule
00:27:21 Application of metamaterial capsule for noise control
00:30:31 Willis coupling of acoustic scatterers
00:33:08 Possible applications of Willis coupling
00:37:16 Theoretical boundary of Willis coupling
00:39:26 Question from Alexey Shcherbakov on non-bianisotropic scattering
00:41:06 Material designs for maximizing Willis coupling
00:45:01 Question from Ivan Toftul on losses
00:47:33 Willis coupling in C-shaped resonators
00:55:56 Question from Alexey Slobozhanyuk about measurement error
00:59:47 Anomalous acoustic reflection with metagratings
01:06:47 Summary
01:09:24 Question from Mikhail Zubkov on anomalous reflection
01:10:06 Questions from Alexey Slobozhanyuk on noise absorbers and prototype manufacturing quality
01:15:31 Questions from Mikhail Zubkov on the realtion of the mata-atom size to its properties and Willis coupling bandwidth
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