How we hear

You will receive detailed information about how we hear from your newborn hearing screening program or Australian Hearing. This table provides a brief overview.The ear can be divided into three sections that work together to conduct sound from the environment to the brain where it is processed. A problem at any site within the ear can lead to a hearing loss. The type of hearing loss will depend on the site of the problem.
Table 1: Understanding the ear and how we hear
Section of the ear Consists of: Function Type of hearing loss
Outer ear
  • Pinna
  • Ear canal
Transmits vibrations (sound waves) from outside the ear, down the ear canal to the eardrum. Problems in the outer ear result in a conductive hearing loss, e.g. ear wax, otitis externa and mictrotia & atresia
Middle ear
  • Eardrum
  • Air-filled cavity containing three tiny hearing bones - the hammer (malleus), the anvil (incus) and the stirrup (stapes)
  • Oval and round window membranes
  • Eustachian tub
The vibration of the eardrum moves the three hearing bones. the stirrup is attached to the oval window membrane and moves the membrane in and out.

The Eustachian tube connects the middle ear with the back of the throat. The Eustachian tube adjusts the air pressure in the middle ear cavity.
Problems in the middle ear result in a conductive hearing loss, e.g. otitis media (glue ear) and cholesteatoma.
Inner ear
  • Cochlea
  • Semicircular canals
The cochlea is a small snail-like structure containing fluid and thousands of microscopic hair cells sitting on a membrane which runs the length of the cochlea. Movement of the hair cells creates electrical impulses which are carried along the auditory nerve to the brain.

The semi-circular canals are responsible for our sense of balance.
Problems in the inner ear result in a sensorineural hearing loss.

Air conduction vs. Bone conduction

Sound waves can reach the cochlea (inner ear) through two routes. Most of what we hear is due to sound waves travelling through the air. Sound waves travel from the outer ear to the middle ear and into the cochlea in the inner ear. This is known as 'air conduction.' Sound waves can also reach the cochlea through vibration of the bones in the head. This is known as 'bone conduction.'

Next: Understanding UHL - Describing the hearing loss

09-Dec-2015 5:40 PM (AEST)