Abstract: 
Metamaterials are man-made media with properties emerging as the collective response of the subwavelength building blocks. The research of acoustic metamaterials has matured into a robust and active field driven by scientific discoveries and application potentials [1].  In this talk, I will discuss our recent progress in sound field control with membrane-type acoustic metamaterials. 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 [2].

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References:
[1]. G. Ma and P. Sheng, Acoustic metamaterials: From local resonances to broad horizons. Science Advances 2, e1501595 (2016). 
[2]. G. Ma, X. Fan, P. Sheng, and M. Fink, Shaping reverberating sound fields with an actively tunable metasurface. PNAS 115, 6638 (2018). 

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Biography: 
Dr. Guancong Ma is currently an assistant professor in the 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 at 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 20 papers in peer-reviewed journals, including in esteemed journals such as Nature Materials, Nature Physics, Nature Communications, Physical Review X, Physical Review Letters.