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  Published:  February 14, 2001 New Scientist Magazine by Duncan Graham-Rowe

A new earpiece that screens out unwanted noise could make yelling to make yourself heard in a crowded bar a thing of the past.

The Personal Active Radio/Audio Terminal (PARAT) earpiece was developed by engineers at the SINTEF research lab in Trondheim, Norway for the Norwegian military. The aim is to help troops talk to each other in noisy tanks, planes or artillery placements.

But it could equally well be used in hands-free sets for cellphones, blocking out most external noise but letting through vital sounds like car horns or safety buzzers. Soccer managers could use it to talk to their earphone-wearing players without shouting themselves hoarse.

The PARAT earpiece will contain a tiny computer, equipped with a program that can recognise particular sounds - the human voice, for example - by their characteristic waveforms. This lets it pick up the sound of people's voices while intelligently filtering out any other types of sounds you choose.

In quiet surroundings PARAT simply tranmits everything it hears. "When there is no need for hearing protection then the device is completely transparent," says Jarle Svean of SINTEF. But, he says, if you are suddenly surrounded by clamour, it switches in so fast that you shouldn't even notice the noise.

The earpieces are mounted in a sealing unit that physically blocks out as much sound as possible. A microphone on the outside picks up sound from your surroundings and relays it to a signal-processing circuit inside that drives a miniature loudspeaker inside the earpiece. An additional microphone next to the speaker monitors sound reaching the ear.

When PARAT is turned on, it first analyses the sound reaching the wearer's ear, looking for voice signals. "It knows what areas of the spectrum voices are produced in, and it looks at the time variation and frequency content of the signal," explains Svean.

The internal microphone ensures that the loudspeaker's volume is at a safe level, and also serves to pick up the wearer's own voice through the ear canal. This was important for the military, says Svean, because it avoids the need to have a microphone boom in front of the mouth where it could interfere with other equipment, such as a gas mask.

PARAT is smart enough to block out droning, cyclical sounds with components within the vocal frequency range. It can even home in on a single voice - so you could shut out the bar room bore.

SINTEF has begun military trials of the system and has spun off a company called NACRE, also in Trondheim, which is planning to commercialise the PARAT technology next year.



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