What is hearing loss?

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Hearing loss or deafness occurs when sound signals do not reach the brain. It is caused by a problem in the hearing system. There are many causes of deafness. Some children are born deaf (congenital deafness) and others may become deaf later (acquired deafness).

Hearing loss can affect one ear (a unilateral loss) or both ears (a bilateral loss). Deafness can be described in levels - mild, moderate, severe or profound.

Types of hearing loss

There are two main types of hearing loss; conductive and sensorineural. It is possible to have a combination of both types and this is known as mixed hearing loss.


This happens when a blockage, such as ear wax, stops sound passing from the outer ear to the inner ear.

Sounds will become quieter and things might sound muffled. The most common cause during childhood is a temporary build-up of fluid in the middle ear known as ‘glue ear’.

It is usually temporary but it can be permanent. 


This is caused by damage to the hair cells inside the inner ear, or damage to the hearing nerve, or both. It makes it more difficult to hear quiet sounds and reduces the quality of sound.

Sensorineural hearing loss is permanent.

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