Hearing Loss: Causes and Types

Our ears pick up sound waves from different directions. Inside our ears, these signals are processed and then transmitted to the brain. But how exactly does hearing work? What do our ears look like and what happens when sounds waves enter the ear canal? Watch this interactive video to learn more.

Types of hearing loss

There are three basic types of hearing loss: conductive hearing loss, sensorineural hearing loss and mixed hearing loss. Each category is marked by which part of the auditory system is damaged. Here we will take a look at the causes of each.

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Conductive hearing loss

Conductive hearing loss is occurs when there is damage or a blockage in the outer and/or middle ear. This can result in sound not being conducted efficiently through the outer ear canal to the eardrum and the ossicles (tiny bones) of the middle ear, leading to a reduction in sound level or the ability to hear faint sounds. This sort of hearing loss can be either acquired or congenital. Thankfully, conductive hearing loss can often be assisted by surgical or medical treatment.
Possible causes of conductive hearing loss include:

  • Blockages of the ear canal by impacted earwax (cerumen) or other foreign objects
  • Ear infection
  • Fluid in the middle ear from a cold or the flu
  • Swimmer’s Ear
  • ‘Glue Ear’ (middle ear infection, often seen in children)
  • Allergies
  • Perforated eardrum, from a bad middle ear infection or an accident
  • Benign tumours
  • Otosclerosis – a hereditary condition where the bone grows around the tiny bones in the middle ear
  • A malformation of the outer ear, ear canal or middle ear
  • Partial or complete closure of the ear canal

Sensorineural hearing loss

This type of hearing loss occurs when there is damage to the inner ear, in particular the cochlea, or when there is something wrong with the nerve pathways from the inner ear to the brain. Sensorineural hearing loss is the most common type of permanent hearing loss, and most of the time it cannot be helped by medical intervention. Sensorineural hearing loss results in the reduction of ability to hear faint sounds, and can make even loud speech unclear or sound muffled.
Some potential causes are:

  • Hereditary and genetic causes
  • Ageing
  • Illnesses, such as mumps, measles or meningitis
  • Excessive exposure to loud noise
  • Head trauma
  • A malformation of the inner ear

Mixed hearing loss

Mixed hearing loss is the result of a combination of sensorineural hearing loss and conductive hearing loss – so both the outer/middle ear and the inner ear are damaged. For example, if one has hearing loss as a result of a middle-ear infection and is also experiencing sensorineural loss due to the ageing process, their condition is classified as mixed hearing loss.