In a crowded room with voices coming from every direction, the human auditory system is incredibly good at homing in on a single voice while filtering out the background jabber. However, computers are not. The new sensor uses a combination of metamaterials and compressive sensing to determine the direction of a sound and extract it from the surrounding background noise.

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 technology may allow iPhone users to more easily talk to digital assistant Siri in loud environments.

"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 University 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," said Xie.

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.

When a sound wave gets to the device, it gets slightly distorted by the cavities. The 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 noises based on these unique distortions.

The researchers tested their invention in multiple trials by simultaneously sending three identical sounds at the sensor from three different directions. It was able to distinguish between them with a 96.7 per cent accuracy rate.

While the prototype is six inches wide, the researchers believe it could be scaled down and incorporated into the devices we use on a regular basis. "This concept may also have applications outside the world of consumer electronics," said Xie.

"I think it could be combined with any medical imaging device that uses waves, such as ultrasound, to not only improve current sensing methods, but to create entirely new ones. "With the extra information, it should also be possible to improve the sound fidelity and increase functionalities for applications like hearing aids and cochlear implants," said Xie.

The study published in the Proceedings of the National Academy of Sciences.

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