Prof. Ping Sheng
Professor Emeritus, HKUST, and Associate of Clare Hall, Cambridge University
Impedance Matching and Designed Acoustic Wave Absorption Spectra
Abstract:
This talk focuses on acoustic metamaterial absorption from the perspective of tuning the impedance of the absorber over a broad frequency regime. In particular, I show that the consideration of the causality constraint can lead to an integration scheme tailored to the target sound source spectrum to be absorbed, with minimal possible absorber thickness. Two schemes will be presented: one for the air-borne sound and another one for underwater acoustics. In air-borne sound, we use Fabry-Perot resonators as the LEGO pieces in the frequency domain– each one giving rise to strong but narrow-frequency-band absorption, to compose the desired absorption spectrum [1]. For underwater acoustics, impedance mis-match of the solid absorber with water can lead to significant reflection at the absorber surface. We propose a novel scheme, involving the use of segmented structures, to form a solid absorber that not only can impedance-match with water, but also naturally form the base material of Fabry-Perot resonators for underwater acoustics, with minimal absorber thickness. That sets the stage for resonator integration that can lead to either tunable or near-total underwater acoustic absorption [2]. An underwater absorber with the average thickness of 8.9mm is shown to absorb 90% of the incident wave from 3 to 20 kHz [2].
[1] Materials Horizon 4, 673-680 (2017); Applied Science, 8, 1247 (2018); Journal of Applied Physics 129, 171103 (2021).
[2] Science Advances 8, eabm4206 (2022).
Affiliations:
Professor Emeritus at Hong Kong University of Science and Technology
Associate of Clare Hall College, Cambridge University
Biography:
Ping Sheng is a Professor Emeritus at HKUST. Since October 2023 he is also an Associate of Clare Hall College in Cambridge University. Prof. Sheng obtained his BSc in Physics from the California Institute of Technology, and PhD in Physics from Princeton University in 1971. After a stay at the Institute for Advanced Study, Princeton, Ping joined RCA David Sarnoff Research Center in 1973. In 1979 he joined the Exxon Corporate Research Lab, where he served as the head of the theory group during 1982-86. In 1994 Ping joined the HKUST as a professor of physics and served as the head of the physics department from 1999 to 2008.
Prof. Sheng is a Fellow of the American Physical Society and a Member of the Asia Pacific Academy of Materials. He served as the Executive Editor of Solid State Communications, a Division Associate Editor of Physical Review Letters and a member of the editorial board of New Journal of Physics. He was awarded the Brillouin Medal by the International Phononics Society in 2013, the Rolf Landauer Medal by the ETOPIM Society in 2018, and the Bloch Prize in 2021. Prof. Sheng was elected a member of the Hong Kong Academy of Sciences in 2019.
Prof. Sheng has published more than 480 papers with a total of over 55,000 citations, and an h-index of 104 (by Google Scholar). He has presented over 350 keynote, plenary or invited talks at international meetings and conferences. His research interests include acoustic metamaterials, nanostructured carbon, giant electrorheological fluids, fluid-solid interfacial phenomena, and effective medium theory of composites. Prof. Sheng’s research has led to the founding of a successful startup company by two of his students, the Acoustic Metamaterials Group.
Prof. Sheng now resides with his wife in Cambridge, UK.