Hearing loss

by Alexandra Middleton | 26 Nov 2013

In Australia, one in six people are affected by hearing loss, a figure that is expected to increase as the population ages. More men than women are affected, and more than half of the population of Australians aged 60 to 70 are hard of hearing.

How do we hear?

The human ear has three parts: the outer ear, the inner ear and the middle ear. In the case of normal hearing the outer ear directs sound waves down the ear canal to the ear drum. This causes the ear drum, along with the three small bones attached to it (hammer, anvil and stirrup) to vibrate.

The movement of these bones causes the hairs and fluid within the cochlear to shift, sending signals to the hearing nerve. The cochlear is where all sound is processed and is the organ that sends noise information to the brain for interpretation. 

Types of hearing loss

Loss of normal hearing occurs in varying degrees of severity. Hearing loss can exist from birth or be acquired later in life as a result of accident, illness, exposure to drugs and chemicals, or as part of the ageing process.

There are three types of hearing loss: conductive, sensoineural and mixed.

Conductive hearing loss
Conductive hearing loss can be present from birth or acquired later in life. It is caused by a blockage or damage to the outer or middle ear, and is characterised by a loss of loudness.

Australian Hearing lists the causes of conductive hearing loss as:

• Blockages of the ear canal by impacted wax or foreign objects
• Outer-ear infection (sometimes the result of swimming)
• Middle-ear infection, a common problem in young children
• Perforated eardrum, caused by a bad middle ear infection or an accident
• Otosclerosis, a hereditary condition where the bone grows around the tiny stirrup bones in the middle ear
• Partial or complete closure of the ear canal

Sensoineural hearing loss
Sensoineural hearing loss can also be present from birth or be acquired later in life. It is caused by damage or malfunction of the cochlea or the hearing nerve. It leads to a loss of loudness as well as a lack of clarity. Treatment using a hearing aide is less effective with this type of hearing loss, as the quantity and quality of sound are both affected.

Australian Hearing lists the causes of sensoineural hearing loss as:

• The ageing process
• Excessive noise exposure
• Diseases such as meningitis and Meniere's disease
• Viruses, such as mumps and measles
• Drugs that can damage the hearing system
• Head injuries

Mixed hearing loss
Mixed hearing loss occurs when there is a problem in the outer, middle and inner ear. As its name suggests, it is a combination of both conductive and sensorineural hearing loss. For example, a perforated eardrum may cause conductive hearing loss in someone who also has sensorineural hearing loss caused by excessive noise exposure.  

Treating hearing loss

If you suspect your hearing is deteriorating, the first step is to undergo a hearing assessment to establish the type and severity of your loss.

Some types of hearing loss, such as those caused by a middle-ear infection, can be corrected with surgery.

The second type of treatment is to have a hearing aid fitted. For individuals who can’t wear an aid, hearing implants are a solution. The most common types of hearing implants are the cochlear implant or bionic ear. These implants are suitable for people of all ages who have sensorineural hearing loss that is severe or isn’t helped by a standard hearing aid.

Preventing hearing loss

As exposure to excessive noise is the leading cause of hearing loss in Australia, accounting for 37 per cent of loss, it’s important to minimise it. Because of the delicate makeup of the cochlear, it is easier than most people expect to cause irreparable damage to your ear. This damage may not be instant, but may accumulate over time due to continual exposure to loud noise.

In order to protect yourself:

• Wear earplugs when at a loud concert or when working with loud machinery.
• Limit the time you spend in loud places. If this is unavoidable, regularly take quiet breaks.
• Don’t be afraid to speak with those around you about ways to reduce noise levels.
• Set your personal and car stereos to a moderate level.