The consequences of exposure to extreme noise levels are not always clearly identified.

Hyperacusis, which is an increased sensitivity to sounds, could result in feeling pain or discomfort when hearing sounds that are usually tolerated by other people.

The exact cause is not yet fully understood but is related to malfunctioning inner ear protection, often as a result of sudden exposure to loud noise.

A temporary threshold shift or hearing loss is usually determined by the severity and length of a relatively short period of exposure. A permanent threshold shift can occur, also as a result of a sudden exposure to an excessively loud noise, known as an acoustic trauma.

Alternatively, noise induced hearing loss is the outcome of continuous exposure over a long period caused by irreversible hearing damage to the hair cells in the inner ear. Years of unprotected daily exposure to extremely high levels of machinery noise in the workplace can ultimately, lead to a serious hearing impairment, often described as industrial deafness.

A condition known as tinnitus may also be a first sign that one or both ears have been damaged by noise due to continued exposure to loud noise. Whistling, ringing or buzzing sounds may suddenly occur or gradually become heard before an effect is felt on hearing. Those who suffer with tinnitus can also have hyperacusis.

Similarly, hyperacusis may come on gradually or suddenly but not all people are affected by an increased sensitivity to the same sounds other people normally register as very minor.

Hyperacusis may be suffered on its own or with a range of other conditions such as depression, migraine, chronic fatigue syndrome and visual over-sensitivity. Sounds which may feel painful or startling can cause reactions of anger, distress or anxiety. After being exposed to an uncomfortable sound, the discomfort can continue for a period of time afterwards and worsen if the sound is heard again. Expecting to hear the sound again can also increase anxiety and discomfort.

Medical research does not yet have a full understanding of the likely different causes of hyperacusis. It is thought that certain hearing system functions, which normally ‘balance’ sounds and protect the system, may be affected. When exposed to a noisy environment, the brain sends noise level ‘information’ back to the inner ear, to enable the ‘volume’ to be reduced and protect the inner ear.

Damage to this feedback mechanism may be an underlying cause of hyperacusis. Problems affecting the vital role the brain plays in processing sound signals received from the inner ear could be another cause of hyperacusis.

Hyperacusis generally first develops after sudden exposure to very high levels of noise or after a head injury, sometimes damaging delicate structures within the inner ear. A specialised audiologist may need to be consulted for thorough audiogram testing and advice on remedial treatment, such as auditory desensitisation, which aims to help improve the level of noise tolerated.