It’s a common belief that people with a hearing loss just can’t hear sounds loudly enough, but it’s more complicated than that. The four main problems caused by hearing loss are:
- Soft sounds can’t be heard.
- Key parts of particular speech sounds may not be heard.
- Sounds are difficult to separate, so voices become jumbled with background noise.
- A reduced range of hearing may make loud sounds intolerable.
What are hearing checks?
Hearing tests simply measure what sounds you can and can’t hear. Your results are marked on a graph called an audiogram which shows how loud sounds need to be before you can hear them—known as your hearing thresholds. This information also lets us know the degree and type of hearing loss you may have. Hearing loss is measured in decibels (dB), which measure intensity, and pitch in hertz (Hz), which measures frequency. Hearing loss is usually described as mild, moderate, severe or profound.
A full hearing assessment with an audiologist is recommended if a hearing check indicates there may be a hearing loss present.
How is hearing tested?
There are a variety of tests that can be used to find out about your hearing. Hearing is tested differently in children and adults.
The simplest way to test hearing is called pure tone audiometry. This involves listening to a range of beeps and whistles, called pure tones, and indicating when you can hear them. The softest sounds you can hear are marked on your audiogram.
Air conduction is when hearing is measured by pure tones played through headphones. The sounds go via the air, down the ear canal, through the middle ear and to the very delicate cochlea in the inner ear.
Bone conduction tests the sensitivity of the cochlea by placing a small vibrator on the mastoid bone behind the ear. Sounds presented this way travel through the bones of the skull to the cochlea and hearing nerves, bypassing the middle ear.
The results of both air conduction and bone conduction hearing tests are marked on an audiogram which can tell us whether the loss is sensorineural or conductive.
Tympanometry is not a hearing test, but a test of how well the middle ear system is functioning and how well the eardrum can move. A small rubber tip is placed in the ear and a little air is pumped into the outer ear canal. If there is a problem in the middle ear, it may show up on this test. The results of tympanometry can indicate the location of a blockage that is causing the hearing loss and if medical treatment will help.
Speech discrimination tests
When hearing is damaged, it is usually not just the volume or quantity of sound heard that is lost. Often the quality of the sound is also distorted. The amount of distortion can be measured using speech discrimination tests. Poor speech discrimination means that voices are distorted and not loud enough.