Hearing tests are carried out for two main reasons:
- as a routine part of a baby’s or young child’s developmental checks
- to check the hearing of someone who is experiencing hearing problems or has a hearing impairment
How the ear works
The ear is a highly sensitive organ that allows you to hear. It is composed of three parts:
- the outer ear
- the middle ear
- the inner ear
Sound enters the outer ear and passes down the ear canal to the eardrum (a thin layer of tissue that separates the outer ear from the middle ear). Sound makes the eardrum vibrate as it travels into the middle ear.
The middle ear is an air-filled cavity between the eardrum and the inner ear. It contains three tiny bones that are commonly known as:
- the hammer (malleus)
- the anvil (incus)
- the stirrup (stapes)
These bones pick up and carry the sound vibrations from the eardrum to the inner ear.
The inner ear contains the cochlea (a fluid-filled chamber that is responsible for hearing) and the vestibular system (the balance organ). Vibrations travel in the fluid of the inner ear and stimulate tiny nerve endings in the cochlea, which turn the vibrations into electrical signals that are fed along the auditory nerve to the brain.
The pitch or tone of a sound is determined by how close the waves are to each other. The closer together the waves are, the more high-pitched the sound is. Pitch is measured in Hertz (Hz). High-pitched sounds are more important for hearing and understanding speech.
Hearing problems
Your hearing may be affected if there is a problem with any part of your ear, such as a blockage in your ear canal or an infection of your outer ear (otitis externa) or middle ear (otitis media). This type of outer or middle ear hearing loss is known as conductive hearing loss, wher the sounds are unable to reach the inner ear hearing organ even though it is working normally. Hearing loss of this type may be temporary and reversible.
If sounds reach the inner ear but are still not heard, the fault lies in the inner ear or, rarely, in the hearing nerve. This is called sensori-neural hearing loss. Inner ear hearing loss may occur for a number of reasons, most commonly as a result of age-related change. Inner ear hearing loss is usually permanent.
Rarely, people are born with an inner ear hearing loss. Approximately 1 in 1,000 babies are born with a permanent inner ear hearing loss.
Hearing tests
Hearing tests are painless procedures. A number of different hearing tests are used to check how well the ears are functioning and their ability to detect different levels of sound. Two tests that are often used to check the hearing of babies are the:
- otoacoustic emissions test (OAE)
- auditory brainstem response test (ABR)
See Hearing tests – how hearing tests are performed for further information about the OAE and ABR tests, plus a number of other types of hearing tests.
For older children and adults, a piece of equipment called an audiometer is usually used to test hearing. This test is called an audiogram and it records how well you can hear different pitches sound.
