CAUSES
of Hearing Loss
Hearing loss occurs when one or more parts of the hearing pathway is damaged or impaired. Hearing loss can range in degrees of severity and affects people differently.
Where & When
This can occur anywhere from the outer ear, middle ear, inner ear and along the auditory nerve up to the auditory cortex in the brain.
Hearing loss can be present at birth or develop later; it can occur suddenly or may develop gradually over several years.
Common causes of hearing loss
- Ageing
- A genetic disorder which may be present at birth or develop later in life
- A middle ear infection
- Prolonged exposure to loud noise
- Head injury
- Exposure to chemicals or medications that damage hearing cells in the cochlea (permanent sensorineural hearing loss)
- Meniere’s Disease
- Otosclerosis
It is possible for a combination of causes to exist in individuals. For example, hearing loss as a result of exposure to harmful noise can be combined with the hearing loss that develops as part of the natural aging process.
Types of hearing loss
- A conductive hearing loss occurs when problems in the middle or outer ear prevent sound from travelling to the inner ear in the usual way
- A sensorineural hearing loss results from damage that has been caused to the sensory hair cells or nerves within the inner ear
- A mixed hearing loss is a combination of conductive and sensorineural hearing loss – there is damage in both the outer or middle ear and in the inner ear
Degrees of Severity
Hearing loss can range in degrees of severity. The most common classifications are mild, moderate, moderately-severe, severe and profound.
Normal Hearing
The quietest sounds that people with normal hearing can ordinarily detect range between -10dB to 20dB.
Mild Hearing Loss
The quietest sounds that people can detect with their better ear range between 20dB and 45dB. Those who suffer from mild hearing loss may experience difficulties following conversations, especially in noisy surroundings. They may not be able to detect sounds such as the hum of a refrigerator, birdsong or a whispered conversation.
Moderate Hearing Loss
The quietest sounds that people can detect with their better ear range between 45dB and 60dB. Those who suffer from moderate hearing loss likely have difficulty following conversations without the assistance of a hearing device. Examples of sounds within this range include a vacuum cleaner operating at 3 metres away, normal level conversation at 1 metre, or a petrol lawn mower at 30 metres.
Moderately-Severe Hearing Loss
The quietest sounds that people can understand with their better ear range between 60dB and 75dB. Those who suffer from moderately-severe hearing loss will benefit from wearing hearing devices. Examples of sounds within this range include dishwasher operating at 1 metre away and air conditioner operating at 2 metres away.
Severe Hearing Loss
The quietest sounds that people can understand with their better ear range between 75dB and 90dB. Those who suffer from severe hearing loss will benefit from wearing power hearing devices. Examples of sounds within this range include a food blender operating 1 metre from the listener or power drill within 2 metres.
Profound Hearing Loss
The quietest sounds that people can understand with their better ear are from 90dB or higher. Those who suffer from profound hearing loss are very hard of hearing and may rely on lip-reading and sign language or they may be cochlear implant candidates. Examples of sounds within this range include a jackhammer, rock concert or jet passing overhead at 350 metres.