"Hyperacusis" is an extreme aversion and hypersensitivity to sounds that are generally not an issue to others.
Electrical and machine noises, as well as sudden high-pitched noises, are usually hard to tolerate for people with hyperacusis (examples are listed in the box on this page).
However, any sound can potentially trigger a reaction in someone with hyperacusis – even the sound of their own voice.
The abnormal reaction may have happened suddenly or got worse gradually over time.
It's very different from the reduced tolerance for noise that most of us have when we're tired or stressed, or reacting to an obviously unpleasant noise, such as chalk scratching a blackboard.
What sort of reaction does hyperacusis cause?
Hyperacusis can be just a minor nuisance for some, with people feeling uneasy or uncomfortable when they hear the noise.
For others, it can have a major impact on life. Low-level noises may be perceived as intrusively loud and may trigger anxiety.
Noise can be painful for people with severe hyperacusis. High-pitched sounds can be felt as 'a nail being driven into the head' and low-pitched thrumming 'like sandpaper moving across the brain'.
Some react by covering their ears or leaving the room. Crying, anger and panic reactions are not uncommon.
As a result, people with hyperacusis may avoid noisy situations and become socially isolated. People with severe hyperacusis may feel suicidal.
Noises that are commonly an issue for children with hyperacusis include:
dogs and barking
laughter, shouting and loud crowds
firecrackers and fireworks
trucks, cars and motorcycles
classroom noise and school bells
sirens, such as ambulances
musical instruments and loud music
electric machines, such as vacuum cleaners, drills and lawnmowers
Children with hyperacusis may struggle at school, where background noise can make it difficult for them to concentrate, thereby affecting their achievement. Some will need professional help in this critical period of their lives, but they may grow out of the problem over time.
However, this does not seem to be the case for adults with hyperacusis. If a sound triggers pain or discomfort, the fear or anxiety this sound provokes only makes the condition worse.
Who is affected?
Hyperacusis is estimated to affect between 7% and 23% of the UK adult population.
It's estimated to affect between 12% and 27% of children, and is particularly common in children with Williams syndrome, autistic spectrum disorder and tinnitus (see below).
What is the cause?
The cause of hyperacusis is unclear.
Some of the theories are explained below, but for many people, hyperacusis can occur for no apparent reason.
Link with hearing loss
Hyperacusis sometimes occurs in people with hearing loss. For people with hearing loss, the sound signals from the inner ear to the brain will be weaker than normal, and it's possible that the brain amplifies these signals too much to compensate, resulting in hypersensitivity.
However, this doesn't explain the cause in those with hyperacusis and no hearing loss.
Underlying medical condition
Many children and adults with hyperacusis have a medical condition, such as:
Lyme disease– a bacterial infection spread to humans by ticks
Bell's palsy – a condition that causes facial paralysis
Addison's disease – a rare disorder of the adrenal glands, near the kidneys
a genetic disorder affecting the brain – such as Williams' syndrome, autistic spectrum disorder or Down's syndrome
an autoimmune disease – any disease caused by the immune system mistakenly attacking body tissues
tinnitus – hearing sounds like whistling or humming from inside the body
Ménière's disease – a rare disorder of the inner ear
It may be that the condition or disease has affected their hearing system in some way and the brain has overcompensated for this, like it does when there's hearing loss.
People with hyperacusis typically experience negative emotions when they hear certain noises.
The sound may be linked to a previous upsetting experience or to negative thoughts they've had about it previously. This means that every time they hear the noise, it automatically triggers a "fight or flight" response and fear, anger, anxiety or irritation.
This would explain why hyperacusis is sometimes associated withpost-traumatic stress disorder (PTSD).
Previous damage to the ear
For some, hyperacusis may have developed after:
a blow to the head or whiplash
persistent ear infections
exposure to loud noise
How is hyperacusis diagnosed?
Hyperacusis is a difficult problem to study and diagnose because it is a subjective experience that is hard to measure.
Anyone who has a severe sound intolerance should see their GP. They may be referred to an ear, nose and throat (ENT) consultant or a hearing disorders specialist (audiologist) to have a hearing test.
This test involves listening through headphones to sounds of increasing intensity, and pressing a button when the sound becomes uncomfortably loud. Self-reporting questionnaires can also be used to measure how much hyperacusis affects the person's life.
How is it treated?
Doctors will want to rule out any medical condition that may be causing hyperacusis. Treating the former may cure the latter.
If the underlying cause isn't certain or there's no obvious treatment, a referral may be needed for retraining counselling and sound therapy.
This therapy is widely available privately, and may be available for people with very severe or persistent hyperacusis. It should only be carried out by someone specially trained in the technique.
Some people may also be advised to have cognitive behavioural therapy (CBT).
What is retraining counselling and sound therapy?
Hyperacusis is thought to result from the brain amplifying sound signals too much. Retraining counselling and sound therapy aim to modify this brain response by removing negative emotional associations to sound.
Retraining counselling teaches patients how emotions and the nervous system may play a role in hyperacusis, and encourages them to reclassify troublesome noises as neutral signals.
Sound therapy helps this process by temporarily desensitising the hearing system so that the individual can go to noisy places without being constantly affected by them. "Desensitising" means listening to and gradually getting used to the sound, which is achieved through the use of noise generators.
What is a noise generator?
Noise generators are small devices worn like hearing aids. They produce a steady, gentle noise with a volume control, allowing the noise level to be turned up or down.
The sound is fed into the ears through an ear mould, which is designed not to block the ear canal, allowing background noise to be heard normally.
It's used to improve a person's ability to tolerate normal exposure to sound – the ear gradually gets used to it and becomes less sensitive.
There is no possibility that hearing will be damaged through using a noise generator, and benefits have been shown even when the generator is not in use.
This is an established method of treating hearing oversensitivity and is used in many audiology departments in the UK.
How is a noise generator used?
Initially, the aim is to increase the length of time the device is worn to at least six hours a day.
The volume should be set so the noise it generates is just about audible, and not intrusive.
If the background noise level is uncomfortable, the volume can be increased to cope with the discomfort.
When the device can be used comfortably for six hours a day without any problems, the level of the noise output should be gradually increased, little by little. The new level should not cause problems, although it may take time to adjust to it.
There is no set level that must be reached, but when the person can tolerate all noises with the generator on, there the volume does not need to be increased any more.
At this point, they shouldn't need to rely on using the device so much, and can gradually reduce the volume or the hours of use.
How long will retraining therapy take?
Typically, after using a noise generator for 12 to 18 months (about 7 appointments), most people find a long-term improvement in their sensitivity, without needing to use the device.
What lifestyle changes might help?
Some people also find the following tips helpful:
relaxation – stress can make hyperacusis worse, so regular exercise such as yoga may help
listening to music – calming music and sounds may also be relaxing, especially at bedtime
support groups – sharing experiences with others who have hyperacusis may be helpful (see Useful Links on this page)
avoid wearing earplugs or muffs – these won't allow the ears to become accustomed to the noise, and may actually make them more sensitive
How might CBT help?
Cognitive behavioural therapy (CBT) is recommended for people with hyperacusis who also have anxiety and depression, or for those who did not benefit from retraining therapy.
CBT is based on the idea that a person's thoughts affect the way they behave. It aims to retrain the way a person thinks in order to change their behaviour – this may be helpful for people who feel a strong emotional response, such as anxiety, to noises.
The aim is to enable the patient to identify and modify their troublesome thoughts. This helps reduce the anxiety and depressed mood, and allows them to accept the noises, which may become less noticeable after a while.
2nd International Conference on Hyperacusis
9-10 July 2015
Venue: Birkbeck College, University of London, UK
Recruitment, misophonia and phonophobia
Recruitment is a type of sound intolerance associated with hearing loss. A weak sound cannot be heard, but when the volume is increased just slightly, it's perceived as becoming very loud very quickly.
Misophonia has been described as an intense dislike of certain body or environmental sounds, such as eating and breathing noises, and repetitive sounds, like the noise of brushing teeth.
Phonophobia has been described as a persistent and abnormal fear of certain sounds.
Symptoms of misophonia and phonophobia may overlap with those of hyperacusis, and some audiologists believe these are different aspects of the same condition.