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Metamaterial-based sensor singles out voice in noisy room

18 Aug 2015  | Ken Kingery

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Smartphones may soon be able solve the classic cocktail party problem by homing in on a single voice in a crowded and noisy room.

Engineers at Duke University have developed a sensor to locate the direction of a sound and extract it from the surrounding background noise. The sensor features compressive sensing and metamaterials—the combination of natural materials in repeating patterns to achieve unnatural properties.

Once miniaturised, the device could have applications in voice-command electronics, medical sensing devices that use waves, like ultrasound, and hearing aids and cochlear implants.

The study was featured in the Proceedings of the National Academy of Sciences.

Prototype sensor

The prototype sensor is tested in a sound-dampening room to eliminate echoes and unwanted background noise.

"We've invented a sensing system that can efficiently, reliably and inexpensively solve an interesting problem that modern technology has to deal with on a daily basis," said Abel Xie, a PhD student in electrical and computer engineering at Duke and lead author of the paper. "We think this could improve the performance of voice-activated devices like smartphones and game consoles while also reducing the complexity of the system."

The proof-of-concept device looks a bit like a thick, plastic, pie-shaped honeycomb split into dozens of slices. While the honeycomb openings may all look the same, their depth varies from hole to hole. This gives each slice of the honeycomb pie a unique pattern.

"The cavities behave like soda bottles when you blow across their tops," said Steve Cummer, professor of electrical and computer engineering at Duke. "The amount of soda left in the bottle, or the depth of the cavities in our case, affects the pitch of the sound they make, and this changes the incoming sound in a subtle but detectable way."

When a sound wave gets to the device, it gets slightly distorted by the cavities. And that distortion has a specific signature depending what slice of the pie it passed over. After being picked up by a microphone on the other side, the sound is transmitted to a computer that is able to separate the jumble of noises based on these unique distortions.


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