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Trendsetters at noisy discotheques may soon be wearing spectacles that
enable them to hear what their friends are saying despite the din. The spectacles,
developed primarily for use by elderly people whose hearing has deteriorated,
work by amplifying sound from directly ahead of the wearer and ignoring
background noise.

Wim Soede of the acoustics and seismic department at Delft University
of Technology in the Netherlands developed his prototype spectacles with
support from the Dutch Science Foundation and Philips Hearing Instruments,
a subsidiary of the Dutch electronics company, which is now developing them
for market.

Realising that traditional hearing aids are not always beneficial because
they amplify everything unselectively, Soede set out in 1986 to build devices
that filtered out unnecessary background din.

His device relies on rows of tiny microphones, so spectacles provided
the obvious vehicle as the microphones can be mounted on the arms and frame.
He eventually devised two prototype pairs of spectacles. The first pair,
which Soede dubbed the ‘broadside array’, has the microphones above the
eyes. The system works by summing sounds that arrive simultaneously at each
of the five microphones, as would happen if someone was speaking directly
in front of the wearer, and amplifying them.

Background noise, by contrast, would strike the ‘broadside array’ at
oblique angles so the sound would reach each of the five microphones at
intervals separated by a fraction of a second. The electronics in the system
would identify these spaced sounds and not amplify them.

In the other, so-called ‘end-fire’ array design, the microphones are
situated along one of the arms and point forward so that the sound waves
from a speaker reach each consecutive microphone slightly later. In this
case the way the signals are processed and amplified is effectively reversed.
The signals to be summed are the ones arriving at the closely spaced intervals
of time, rather than the ones that are arriving simultaneously. This means
that background noise arriving simultaneously at each microphone would not
be amplified.

In listening tests conducted at the audiological centre of the ear,
nose and throat department at the Rotterdam University Hospital, Soede managed
to perfect prototype spectacles that lowered the level of the background
noise by 7 decibels. He says that this attenuation helped wearers to distinguish
50 per cent more speech than was possible unaided.

While Soede has focused mainly on the elderly and hard-of-hearing, he
says that his spectacles are equally adaptable to discotheques and noisy
parties where people, even with normal hearing, may find it tough to hear
conversation. He envisages people taking ‘trendy discotheque specs’ with
them in their pockets on an evening out so that they can talk as well as
dance.

He says that the microphones are expensive, at $13 each, but the glasses
could still work out cheaper than traditional hearing aids.