Better understanding of hearing loss begins by understanding how we hear. The diagram below illustrates the steps involved.
- Sound waves are collected by the outer ear and channeled along the ear canal to the eardrum.
- When sound waves reach the eardrum, the impact creates vibrations which are transferred through a series of three tiny bones.
- The third of these bones is connected to a delicate, snail-shaped structure called the cochlea. The cochlea is filled with fluid and lined with thousands of microscopic hairs.The vibrations are transmitted to the fluid in the cochlea, where the hair cells are bent by the wave-like action of fluid inside the cochlea. The bending of these hairs sets off nerve impulses that are then passed through the auditory nerve.
- The auditory nerve carries the signal to the hearing centre of the brain, which translates the impulses into what we perceive as “sounds”.
Symptoms of hearing loss
Recognising a hearing loss in yourself, or someone you know is the first step toward improving the situation.
- Difficulty hearing high-pitched sounds, such as the voices of women and children
- Difficulty hearing at public gatherings and events
- Difficulty understanding conversations within a group of people, or on the telephone
As hearing loss can gradually develop over several years, most people are not aware of the extent of their loss until family or friends bring it to their attention. Even then they might deny that they have difficulty hearing.
People with mild hearing loss often use the following tactics to cope with the situation:
- Turning up the volume on the TV to a level that disturbs others
- Consistently asking people to repeat themselves, or to speak more loudly
- Avoiding social situations such as restaurants or parties, where noise can make it difficult to hear conversation
- Turning the head to one side while listening
Although these habits can help the individual with hearing loss in some situations, the hearing loss is most likely depriving them of a wide range of life’s sounds. Eventually, as the hearing loss progresses, the above techniques won’t provide adequate hearing assistance.
Causes of hearing impairment
Most often a hearing loss develops gradually and painlessly. Hearing can be damaged by:
- Exposure to loud or constant noise
- Inherited medical conditions
- The natural aging process
- Traumatic injury
Types of hearing loss
- Conductive hearing loss occurs when the eardrum, bones and membranes don’t properly transmit vibrations to the cochlea. Causes include traumatic head injury or birth defects, wax occlusion and middle ear infections.
- Sensorineural hearing loss is characterised by deterioration of hair cells in the cochlea. Causes include the aging process and excessive exposure to loud noise.
- Mixed hearing loss involves a combination of both conductive and sensorineural hearing loss.