报告题目：Novel Ways of Sound Field Control with Acoustic Metamaterials

报 告 人：Prof. Guancong Ma (Hong Kong Baptist University）

报告时间：2019年4月24日（周三）下午14:30

报告地点：物理学院新楼五楼多功能厅

报告摘要：

The research of acoustic metamaterials has matured into a robust and active field driven by scientific discoveries and application potentials. In this talk, I will discuss our recent progress in sound field control with membrane-type acoustic metamaterials. In the first part, I will show the way to reshape reverberating sound field in a room by building a “spatial sound modulator” which is based on a metasurface that is an array of actively controllable metamaterials. We show the functionality of the on-demand creation of quiet zones and acoustic hotspots at audio frequencies anywhere in a reverberating room. This is the first realization of the adaptive wavefield shaping for acoustic waves. In the second part, I will show that by building a subwavelength absorber for spherical waves, the focal spot formed by an isotropic converging wave in 3D can become smaller than the diffraction limit. The idea is based on the observation that diffraction limit is the consequence of the interference between incoming and outgoing waves, therefore by removing a majority of the outgoing energy with a subwavelength absorber, the total field profile is drastically modified, leading to sub-diffraction focusing. This result can also be interpreted as the realization of a stand-alone anti-causal Green’s function up to the surface of the absorber. The absorber also plays an important role of an acoustic sink, which is the time-reversal counterpart of a source.

报告人简介：

Dr. Guancong Ma is currently an assistant professor in Department of Physics, Hong Kong Baptist University. Dr. Ma received BSc in applied physics in South China University of Technology (Guangzhou, China) in 2007, and then PhD in physics in Hong Kong University of Science and Technology in 2012. After that, he became a postdoc fellow in Institute for Advanced Study and Department of Physics, Hong Kong University of Science and Technology until 2017. Dr. Ma’s studies classical wave physics. His researches focus on acoustic waves and elastic waves. The topics of interests include acoustic metamaterials, elastic metamaterials, phononic crystals, wavefield shaping, non-Hermitian wave system, etc. He has published over 20 papers in peer-reviewed journals, including in esteemed journals such as Nature Materials, Nature Physics, Nature Communications, Physical Review X, Physical Review Letters, etc. He has also published a review article on acoustic metamaterials in Science Advances, and a review article on topological acoustics and mechanics in Nature Reviews Physics.

邀请人：肖孟 教授