Physicists in Hong Kong have discovered an experimental way to achieve perfect sound absorption. Photo by PathDoc/Shutterstock

HONG KONG, Sept. 12 (UPI) -- Physicists from Hong Kong University of Science and Technology have achieved the goal of almost perfect silence via total sound absorption.

Instead of building multi-layered gradient-index material meant to absorb all frequencies -- which would be quite thick considering the amount of wavelengths there are -- the researchers used two resonators to come close to completely canceling out sound waves.


In a paper published Friday in the journal Applied Physics Letters, researchers explain their use of destructive interference to halt the scattering of sound waves, thus achieving near perfect quiet.

Researchers tuned two resonators to the same frequency, which was matched to the background sound's average impedance. The result was absolutely no audible backscattering. They used decorated membrane resonators to complete their two experiments. The first consisted of a flat panel DMR and a pair of coupled DMRs; the second used a tube-ventilated DMR and a sidewall device backed by a cavity.

The rate of sound absorption at the end of both of these experiments came up to 99.7 percent -- almost complete silence.