Hearing loss can occur in either one of two ways, or a combination of both.
Conductive Hearing Loss
Conductive hearing loss occurs when the outer or middle ear is dysplastic or does not work properly. Consequently, sound waves cannot be efficiently conducted to the inner ear. In case of a temporary dysfunction, it is often possible to correct conductive hearing loss with surgery and/or treatment with medication.
Common causes of conductive hearing loss include:
1. Injury of the outer ear itself Blockage of the ear canal due to ear wax (cerumen) or other small objects like food, beads or insects
2. Infections of the outer or middle ear
3. Perforation of the tympanic membrane
4. Congenital deformities (e.g. Down syndrome, Franceschetti syndrome, Treacher Collins syndrome or Achondroplasia (dwarfism)
Sensorineural Hearing Loss
Sensorineural hearing loss is the most common type of hearing loss. It has its origin in the inner ear or along the auditory nerve. Most commonly, the damage occurs in the inner ear (cochlea).
In this instance, the hair cells in the cochlea are damaged and cannot transmit neuro-electrical impulses to the brain. Sensorineural hearing loss can be congenital (present at birth) or acquired after birth.
Common congenital causes include:
1. Hereditary factors
2. Viral infections
4. Birth trauma such as anoxia
5. Acquired causes include:
6. Reactions to ototoxic drugs (damaging to the hearing system)
7. Head injury
8. Noise exposure
Mixed Hearing Loss
The transmission of sound can be blocked in multiple places along the auditory path. When a hearing loss occurs from conditions in the inner ear as well as the outer and/or middle ear, this is known as mixed hearing loss. An example of a mixed hearing loss may be someone with inner ear damage due to exposure to noise in their workplace over many years, who also currently has an infection that has led to a fluid build-up in the middle ear.
Noise Induced Hearing Loss
Given the impact of noise, it is not surprising that males are considerably more likely to have hearing loss than women – including being twice as likely to have a moderate to severe hearing loss.
These days, people are more aware of the damage that noise can do to their hearing. This is illustrated through mandatory provision of ear protection on work sites and within factories. Nevertheless, every day millions of people are exposing themselves to noise levels that will lead to long-term damage to their hearing, including the use of personal stereo systems.
This diagram illustrates the time it takes to cause permanent damage to your hearing when you’re exposed to different levels and sources of sound.