Sound-bouncing membrane could make plane cabins 1,000 times quieter

A more peaceful flight could be on the horizon thanks to researchers at North Carolina State University and MIT.

Michael Franco
Freelancer Michael Franco writes about the serious and silly sides of science and technology for CNET and other pixel and paper pubs. He's kept his fingers on the keyboard while owning a B&B in Amish country, managing an eco-resort in the Caribbean, sweating in Singapore, and rehydrating (with beer, of course) in Prague. E-mail Michael.
Michael Franco
2 min read

A new membrane applied to the honeycomb insulation in planes could act like a drum, bouncing engine noise away. Yun Jing

Even when airplane cabins aren't filled with wailing babies, safety announcements and flight details, they are still pretty noisy places due to sounds and vibrations from jet engines. However, a new rubber membrane could make plane cabins significantly more peaceful.

Plane cabins are currently insulated with a strong, light honeycombed material. While it's great at keeping weight down -- and therefore, fuel economy up -- it's not so great at blocking sound.

North Carolina State University and MIT researchers, whose work was detailed last week in Applied Physics Letters, figured out that by putting a rubber membrane measuring 0.25 mm thick (about 0.01 inches) on the honeycomb, they could bounce up to 1,000 times more sound waves away from the cabin than is currently possible. The membrane is particularly effective at eliminating low-frequency noises, like those that come from the plane's massive engines.

While that seems like a no-brainer to any frequent flier, airlines might not be so quick to adapt the material. A major hurdle is that the membrane adds 6 percent to the overall weight of the plane, which would then raise fuel costs. However, Yun Jing, an acoustician at North Carolina State University who helped develop the membrane method, told Scientific American that a compromise might be possible. A thinner membrane would add just a few percentage points in weight, while still offering significant sound reduction.

Such a solution might actually be even more beneficial, as Jing said some people find engine noise comforting. "Some people say they actually want to hear the sound of the engine," he told Scientific American. "They don't want the cabin to be too quiet. They want to make sure the plane is still flying."

And don't forget, a little engine noise helps drown out the wail from that crying baby in row 15.