What is deafness and hearing loss?

Deafness, or hearing loss, happens when one or more parts of the ear are not working effectively. This affects how well someone can hear sound. 

This can in turn affect how a child develops speech, as they cannot hear certain sounds clearly. 

How does the ear work?

The ear has 2 main functions.

• It receives sound and converts it into signals that the brain can understand.
• It helps us to balance.

The 2 functions are closely related.

The ear is the first part of the hearing system. The outside part of the ear is called the pinna. It acts like a funnel and catches sound waves and directs them down the ear canal. The waves then cause the eardrum to vibrate.

These vibrations are passed across the middle ear by 3 tiny bones: the malleus, incus and stapes (sometimes known as the hammer, anvil and stirrup). These bones pass the vibrations into the cochlea.

The cochlea looks like a snail’s shell. It's filled with fluid and contains thousands of tiny sound-sensitive cells. These cells are known as hair cells. Unlike other cells in the body, they do not grow back when damaged.

The vibrations entering the cochlea cause the fluid and hair cells to move, much like the movement of seaweed on the seabed when waves pass over it.

As the hair cells move, they create a small electrical signal. The auditory nerve carries these signals to the brain where they are understood as sound.

For an ear to work fully and pick up sound, all of these parts must work well.

Why are some people deaf?

There are lots of reasons why someone may be deaf. Some people are born deaf, which is called congenital deafness. Other people become deaf later, which is called acquired deafness.

Sometimes doctors may not know why someone is deaf. Even with lots of testing, sometimes the exact reason cannot be identified. This can be difficult for families seeking answers and highlights the need for ongoing research to better understand childhood deafness.

Find out more about the causes of deafness.

Different types of deafness

There are 4 types of deafness: conductive, sensorineural, central, and mixed. It can be helpful for you to know and understand your child’s type of deafness. You can ask your child’s audiologist if you’re not sure.

More information about different types of deafness can be found in our Understanding your child’s hearing test resource.

Conductive deafness

Conductive deafness is when sound cannot pass efficiently through the outer or middle ear to the cochlea and auditory nerve.

Conductive deafness may be temporary or permanent.

Permanent conductive deafness can be caused by conditions such as microtia and atresia.

Temporary conductive deafness can be caused by a blockage such as wax, or by glue ear.

Sensorineural deafness

Sensorineural (or nerve) deafness is when there’s a problem in the inner ear (most often because the hair cells in the cochlea are not working properly) or auditory nerve. It is permanent.

Sensorineural deafness can have a range of causes including genetic conditions or infections.

Mixed deafness

Mixed deafness is when there’s a combination of sensorineural and conductive deafness, such as when a child has glue ear and permanent sensorineural deafness.

Central deafness

Central deafness is the rarest form of deafness. It is caused by a problem in the brain’s central auditory processing system. Usually, the ears are healthy, but something (usually a stroke) has affected part of the brain that processes sound.

Deafness can be in both ears or just in one. Deafness in one ear is called unilateral deafness.

There are also different levels of deafness - mild, moderate, severe and profound - which describe which sounds can be heard without technology.