Sound check

Georgia Tech Research Institute (GTRI) research engineer Jason Nadler has developed a new material that can reduce the noise of aircraft engines.

The honeycomb-like structure is composed of many tiny tubes or channels that can reduce sound more effectively than conventional methods.

Most sound-deadening materials - such as foams or other cellular materials comprising many small cavities - exploit the fact that acoustic waves resonate through the air at various frequencies.

Just as air blowing into a bottle produces resonance at a particular tone, an acoustic wave hitting a cellular surface will resonate in certain-size cavities, thereby dissipating its energy. The drawback with the approach is that it only reduces noise at certain frequencies.

Nadler’s research involves broadband acoustic absorption, a method of reducing sound that doesn’t depend on the frequency of the noise or resonance.

In his approach, tiny parallel tubes in porous media such as metal or ceramics create a honeycomb-like structure that traps sound regardless of its frequency. Instead of resonating, sound waves enter the channels and dissipate through a process called viscous shear.