AMADEus Seminar - Prof. Ping Sheng - Monday 4 december 2017 - 4:30 pm - CRPP (Amphi)

Abstract: Even in the 21st century, noise still constitutes a major environmental problem, with the low frequency noise being especially pernicious. One reason for this state of affairs is that the conventional sound absorbing materials have fixed absorption spectra which can only be adjusted by increasing or decreasing the thickness. It would be most desirable if a sound absorber can be designed to fit the noise spectrum, with a minimum allowed thickness. Such sound absorbing structures can now be realized through a design recipe that incorporates the causality constraint on the acoustic response1. The strategy involves the recognition that the causal nature of the acoustic response dictates an inequality that relates the two most important aspects of sound absorption: the absorption spectrum and the sample thickness. We use the causality constraint to delineate what is ultimately possible for sound absorbing structures, and denote those which can attain near-equality for the causality constraint to be ‘‘optimal.’’ Anchored by the causality relation, a design strategy can be formulated for realizing structures with target-set absorption spectra and a sample thickness close to the minimum value as dictated by the causality constraint. By using this approach, we have realized a 10.86 cm-thick structure that exhibits a broadband, near-perfect flat absorption spectrum starting at around 400 Hz, while the minimum sample thickness from the causality constraint is 10.36 cm. To illustrate the versatility of the approach, two additional optimal structures with different target absorption spectra are presented. This ‘‘absorption by design’’ strategy would enable the tailoring of customized solutions to difficult room acoustic and noise remediation problems.

1. Materials Horizons 4, 673-680 (2017).

Speaker biography
Ping Sheng is the William Mong Professor of Nanoscience and Chair Professor of Physics at HKUST. He 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, 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 a Division Associate Editor of Physical Review Letters and is currently a member of the editorial board of New Journal of Physics, and an Executive Editor of Solid State Communications. He was awarded Technology Leader of the Year by the Sing Tao Group in 2002, the Brillouin Medal by the International Phononics Society in 2013, and the National Natural Science Award (second class) by the State Council of the People’s Republic of China in 2014.
Prof. Sheng has published more than 460 papers with a total of over 30,000 citations, with an h-index of 84 (by Google Scholar). He has presented over 300 keynote, plenary or invited talks at international meetings and conferences. His current research interests include acoustic metamaterials, superconductivity in carbon nanotubes, nanostructured graphene, giant electrorheological fluids, fluid-solid interfacial phenomena, and effective medium theory of composites.