It's a common belief that hearing-impaired people just can't hear sounds loudly enough, but it's more complicated than that. The four main problems caused by hearing loss are:
Hearing tests measure what sounds you can and can't hear. Our clinicians can use a variety of tests to find out about hearing. They will plot your test results on a graph called an audiogram. This graph shows how loud sounds need to be before you can hear them - called your hearing thresholds.
Hearing loss is measured in decibels (dB) and pitch in hertz (HZ). Decibels measure intensity, and hertz measures frequency. The results of a hearing test indicate the degree and type of hearing loss.
How is hearing tested?
Children and adults hearing is tested differently. Click here to find out about hearing tests for children.
The most simple test of hearing ability is called pure tone audiometry where you listen to a range of beeps and whistles, called pure tones, and indicate when you can hear them. The loudness of each tone is reduced until you can just hear the tone. The softest sounds you can hear are your hearing thresholds.
Your hearing may be tested with pure tones presented through headphones. This measurement is called air conduction. The sounds go via the air, down the ear canal, through the middle ear, and to the very delicate cochlea in the inner ear.
The sensitivity of the cochlea can also be tested 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. This type of testing is called bone conduction.
Interpreting the results of air and bone conduction tests
Air conduction and bone conduction indicate to the clinician where the hearing problem is located. If the bone conduction hearing thresholds are the same as the air conduction thresholds, this indicates there is no blockage of sound in the outer or middle ear. The hearing loss may be caused by a loss of sensitivity in the cochlea or hearing nerve. This type of loss is called sensorineural hearing loss.
If the bone conduction hearing thresholds are normal, but there is a loss of hearing with air conduction, this indicates that the cochlea is normal and healthy, but there is some blockage to sound in the middle or outer ears. This is called a conductive hearing loss.
It is possible to have a sensorineural and conductive hearing loss - called a mixed hearing loss.
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 may help.
Speech discrimination tests
The ability to hear speech is a function of the ability to detect the sounds of speech, and the ability to understand speech. The range of audible sounds, not just the degree of hearing loss, can vary considerably from person to person.
Unfortunately, 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.