Different types of hearing loss
- Conductive hearing loss
Sound doesn’t travel properly (“conduct”) from the outside to the inner ear. Causes include infection, wax blockage and trauma. This can sometimes be corrected by surgery or simple amplification.
- Sensorineural hearing loss
Generally a problem with the inner ear, or cochlea, in which the sensory hair cells do not detect sounds of certain frequencies as well as they should. Causes include ageing, excessive noise exposure and some viral infections. Most hearing impairments fall into this category, so this is the problem that most hearing aids seek to address.
- Mixed hearing loss
A mixed hearing loss occurs if both conductive and sensorineural hearing losses are present.
With a sensorineural impairment, you might lose only low or only high-frequency sounds, for example, so you would need a hearing aid that amplified frequencies very selectively.
Not only that, but in an environment where there are many sources of sound (such as someone talking over the sound of traffic), you’d want to amplify only the soft sounds that you can’t hear rather than making the louder sounds painfully unbearable.
Finally, you need a hearing aid to work in subtly different ways in different listening environments, such as at home, on a busy street, or in a noisy restaurant.
Long-term studies suggest that without proper stimulation, the brain can “forget” how to hear. This is known as auditory deprivation and results in permanently reduced speech understanding which cannot be restored with hearing aids.
Hearing loss in children
The most common cause of hearing loss in children is due to ear infection, or otitis media. This can usually be successfully treated. In rare cases, hearing loss may be present from birth or acquired due to infection or trauma. In these cases hearing aids may be helpful.