Sonic Cloak Makes Users Invisible to Sound Waves

Author:  Mao Frances

Date:  January 2008

It's an audiophile's worst nightmare: scoring impossible-to-get tickets to the best concert of the year, and having to sit directly behind a giant pillar of rock! If this though has ever frightened you, then worry no more!

Researchers at Duke University have laid the theoretical groundwork for a sonic invisibility cloak. Such a cloak would allow sound waves to travel around an object and emerge on the opposite side, without distortion.

"We've devised a recipe for an acoustic material that would essentially open up a hole in space and make something inside that hole disappear from sound waves," said Steven Cummer, Associate Professor of Electrical and Computer Engineering at Duke.

Possible applications of this technology would be to shield submarines from sonar detection, and to improve acoustics in concert halls. However, because the sound cloak would require materials that do not exist in nature, specially constructed polymers would have to be manufactured.

The "invisibility cloak" previously demonstrated by another research team at Duke allowed light (electromagnetic waves) to travel around objects seamlessly., Cummer's team decided to start from a microwave cloak, and then worked to derive the specifications needed to prevent the cloak from reflecting sound waves.

"It was hard for me to imagine that something you can do with electromagnetic waves could be completely undoable for sound waves," said Cummer. "We've now shown that both 2-D and 3-D acoustic cloaks theoretically do exist."

Written by Frances Mao

Reviewed by Pooja Ghatalia

Revised by Pooja Ghatalia.