IT鈥橲 no fun yelling to make yourself heard at a party or in a crowded bar.
And sports coaches know just how tough it is to talk tactics to a team above the
roar of a crowd.
What you need in these kind of noisy environments is selective hearing:
something that blocks the noise you don鈥檛 want to hear, leaving the sound you do
want coming through loud and clear. And engineers at the SINTEF research lab in
Trondheim, Norway, have come up with just the thing.
Its Personal Active Radio/Audio Terminal (PARAT) earpiece was developed for
the Norwegian military 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.
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The idea is that the PARAT earpiece will contain a tiny computer, equipped
with a program that can recognise particular sounds鈥攖he human voice, for
example鈥攂y their characteristic waveforms. This lets it pick up the sound
of people鈥檚 voices while intelligently filtering any other types of sounds you
choose.
In quiet surroundings PARAT simply tranmits everything it hears. 鈥淲hen there
is no need for hearing protection then the device is completely transparent,鈥�
says Jarle Svean of SINTEF. But, he says, if you are suddenly surrounded by
clamour, it switches in so fast that you shouldn鈥檛 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鈥檚
ear, looking for voice signals. 鈥淚t knows what areas of the spectrum voices are
produced in, and it looks at the time variation and frequency content of the
signal,鈥� explains Svean.
The internal microphone ensures that the loudspeaker鈥檚 volume is at a safe
level, and also serves to pick up the wearer鈥檚 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鈥攕o
you could shut out the party 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.