The theory here is that children with autism have a non-linear frequency response in their hearing range, so that, to an  child, sounds at certain pitches seem hundreds of times louder than they should be. It is a fact that many such children are hyper-sensitive to certain sounds, and this incidentally is another symptom of mercury poisoning in adults.

There is nothing wrong with their ears – it is the processing of the sound in the brain which is malfunctioning. It would appear that, by listening to music with certain modifications, extra “synaptic routing” is created in the brain which improves this processing and creates a “flatter” frequency response. Out of 28 studies of auditory integration training, 23 found measurable behavioural improvements in children with autism. The most popular method is that of Dr Guy Berard, available in the UK at the Sound Learning Centre. The Johansen method, also used for dyslexia, has the advantage that it can be employed at home by listening to CDs through headphones.

The most celebrated case of success with AIT is documented in the book The Sound of a Miracle by Annabel Stehli, whose daughter emerged from Autism thanks to this treatment. The most famous quote from the book is that after recovering, Georgiana wanted to play in the rain because “it does not sound like machine-gun fire anymore”, a statement that provides great insight into the hardship endured by those afflicted with autism.

Since the days of Dr Berard, other systems such as Fast Forword have been developed using computer-modified speech to assist language processing, with the modifications gradually phased out adaptively according to progress.

Tests for auditory processing can be carried out by Dr Sirimanna at Great Ormond Street Hospital in London, sometimes on the NHS via GP referral. As well as being a sound basis on which to base treatment, these test results can be a useful means of obtaining education support in school where auditory processing may be disrupted by classroom noise.