Babies will benefit from portable hearing test

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A REVOLUTIONARY hearing test, using a tiny plug connected to a laptop computer, is helping to trace hearing defects in babies like Kirsty Bray.

The test is portable, can deliver a result in two minutes, does not need to be carried out in silent surroundings and is suitable for babies just a few days old. It will reveal whether Kirsty, aged four months, has a hearing problem and exactly at which frequency it occurs.

It was invented by David Kemp, Professor of Auditory Biophysics at the Royal National Throat, Nose and Ear Hospital, London. The system - otoacoustic emission testing - is now being introduced at NHS hospitals.

The test should allow the early identification of babies born with serious hearing defects. Half of these children do not have any risk factors and problems may not be picked up until they are three- or even five-years-old resulting in difficulties with speech and learning.

The test was developed after Professor Kemp discovered that thousands of cells, known as outer hair cells, within the cochlea in the inner ear, bounce around in response to sound. The energy released by this movement builds in a chain reaction and acts as an amplifier, allowing the cochlea, which is just two or three millimetres high, to hear even quite distant sounds clearly.

Professor Kemp said: 'It is as if we all have a hearing aid inside our ears. When this hearing aid does not work for any reason you have problems.'

The idea for the new hearing test came when Professor Kemp, listening to his own ears with a powerful microphone, discovered that when the outer hair cells react to an incoming sound, some of the amplified noise spills back out of the ear and can be recorded and measured. The result is that the tiny plug in Kirsty's ear broadcasts a series of gentle clicks of different frequencies and, is able to record the ear's response. The computer analyses this and, seconds later, presents the information as a graph showing how well Kirsty hears at different frequencies.

Until now the only ways of examining a baby's hearing have been using a manual test, the accuracy of which varies with the skill of individual examiners.

(Photograph omitted)