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How is hearing tested?

The simplest test is called pure tone audiometry where the patient listens to a range of beeps and whistles and presses a button to indicate what he or she has heard. The volume of each tone is gradually reduced.

The softest sounds the patient can hear (their 'hearing thresholds') are marked on an audiogram.

Air conduction

When hearing is measured with pure tones presented through head-phones, the measurement is called air conduction. The sounds go via the air, down the ear canal, through the middle ear, and to the very delicate organ of hearing in the inner ear - the cochlea.

Bone conduction

The sensitivity of the cochlea can also be tested by placing a small vibrator on the mastoid bone behind the ear, and measuring the softest sounds that can be heard.

Sounds presented this way travel through the bones of the skull to the cochlea and hearing nerves, bypassing the middle ear.

The air conduction and bone conduction hearing levels on the audiogram can tell us a lot about where the hearing problem is.

Tympanometry

This 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. For example, if there is very little movement of the eardrum, it may indicate fluid behind the drum as a result of a middle ear infection.

If the results of tympanometry are abnormal this may indicate a problem in the outer or middle ear and medical treatment may help.

Speech Perception Testing

The ability to hear speech is a function of two abilities:

An audiogram shows the degree and type of hearing loss, but to measure a person's 'speech discrimination' - how well speech can be understood - special tests are used. For example, words may be presented (usually at different levels of loudness) which the hearing impaired person has to repeat. Someone who has a problem with understanding the words, even when they are loud enough, may find the benefit provided by a hearing aid will be limited. Generally speaking, the greater the hearing loss, the poorer the speech discrimination.

Although hearing loss is measured in decibels, it is usually described in terms of degree of impairment for hearing conversational speech.

If you have any queries about how hearing is tested, please feel free to contact us.