The greatest fans of middle-of-the-road chart-toppers such as Enya and Fleetwood Mac would hesitate before claiming medical benefits from listening to their CDs. But such mellow sounds are at the heart of a radical new technique that claims dramatic improvements in the speech and behaviour of autistic and other disturbed children.

Admittedly, the tracks sound as though they are fresh from the turntable of a demented scratch DJ - notes sigh and wobble, the volume rises and falls. But there is growing evidence that listening to this doctored rock for twice a day for 10 days can change the way sounds are registered in the brain.

Autism, which afflicts an estimated 115,000 people in Britain, is notoriously hard to treat. The sufferers live in a withdrawn world, often incapable of any human communication and given to strange ritualistic behaviour. Anything that offers hope is clutched at. The parents whose children have done auditory integration training (AIT) have no doubt that it works.

At the age of three, Joshua Alderman was diagnosed autistic and his behaviour, says his mother, Tracy Alderman, was obnoxious. 'He would have tantrums for a whole day, his only communication was to say what he wanted. Meal times were horrendous; food had to be cut into exactly the same-sized squares and if one was wrong he would have a fit.'

Then, in April, Joshua started a course of AIT at the private Hale Clinic in London. The practitioner is Aditi Silverstein, an American speech and language pathologist who has her own AIT centre in Virginia. For half an hour, twice a day for 10 days, Joshua put on headphones and listened to the treated music. 'Most of the parents don't believe that the children will sit still for that long,' says Ms Silverstein, 'but they nearly all do.'

Four months later, Joshua's mother describes the effect on him as 'amazing, uplifting'. Before, she says, it was impossible to reason with him, but now she can discuss things. 'Going out used to be a minefield but we have just been on the first holiday since he was born. His behaviour is still bad at times but instead of lasting for a day, it is over in an hour.'

Joshua's NHS paediatrician has seen the difference too, and his speech therapist declared that his spoken language and grasp of concepts had much improved.

What can be going on? How can listening to tampered Peter Gabriel change speech and behaviour? 'We don't know exactly what's happening on a neurological level yet. However, there is no shortage of theories - about 17 according to one recent research paper,' Ms Silverstein said.

She believes that many these children are suffering from what might be called auditory dyslexia. 'They have difficulty with their hearing, although not the sort that shows up on a conventional audiogram. They have problems processing certain frequencies, with the result that their auditory world is mangled.' One mother said of her son: 'It's as though he's permanently at Heathrow and hearing everything through the Tannoy system.' Not surprisingly, they believe, the frustration this causes leads to bad behaviour.

In AIT, frequencies that are believed to be causing the problems are isolated and the music for the sessions is then electronically filtered and made louder or softer to emphasise them. 'This forces the brain to listen to them afresh because it doesn't know what to expect. This changes the way auditory information is received, so the children are less likely to block out sounds. Afterwards, the children actually hear the world differently,' she said.

Acute sensitivity to noise is certainly something many children with learning and behaviour difficulties experience. For instance, 10-year-old Christopher Woods, a young American patient of Dr Silverstein, used to be hyperactive and easily distracted. Certain sounds, such as the buzz of chainsaws could make him hysterical. But after treatment at Silverstein's centre at Roanoke in Virginia, he became much calmer. 'He's not perfect, but he's much mellower and less aggressive. We now realise that he was being distracted by sounds that we didn't think were a problem, but they were for him.' his mother said.

The connection between auditory problems and learning difficulties was highlighted by a report last month of work from Dr Glen Rosen of Beth Israel Hospital in Boston. He found that in the brains of dyslexics the region of the left brain that deals with hearing has fewer neurons for dealing with fast staccato sounds. than a normal brain. 'What this means is that dyslexics may have difficulty constructing a mental dictionary that keeps track of what letters sound like,' he suggested.

Although AIT has claimed dramatic success with autism it was originally developed to help children with learning difficulties such as dyslexia. It originated in France more than 25 years ago and was developed by a French physician, Guy Berard, who treated 1,850 dyslexics, claiming positive results for 1,410. However, it remained little more than a curiosity until four years ago when it took off in America with the publication of a book, The Sound of a Miracle, by the mother of a severely autistic girl, Georgianna Stehli Thomas. She was treated by Dr Berard and improved so dramatically that she eventually graduated, and got married.

The AIT literature has pages of anecdotal successes, much of it heartbreaking: a five-year-old who went to the toilet on his own; a 12-year-old who said 'I love you' without prompting.

But theories and anecdotes are not enough. What about clinical trials? A small study last year at the University of Virginia found a dramatic improvement in auditory ability in three out of 11 patients, while the behaviour of the others improved significantly. A detailed study undertaken this year at Upper Valley Medical Centres, Troy, Ohio looked at 13 subjects with attention deficit hyperactivity disorder treated with AIT. It found improvements in behaviour and brainwave pattern.

A large clinical trial is now needed to prompt greater acceptance of AIT by professionals.

The Hale Clinic is holding a free seminar on AIT on 5 October. Details of this and treatment on 071-631 0156.

(Photograph omitted)