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Audiology How the Test is Performed:
General screening may be used to estimate the need for
audiography. Specific procedures may vary, but they generally involve occluding one ear at a time and checking for the ability to hear whispers and then spoken words or the sound of a ticking watch. A tuning fork may be used to test your general ability to hear by air conduction and bone conduction. The tuning fork is tapped and held in the air on each side of the head to test the ability to hear by air conduction. It is tapped and placed against the mastoid bone behind each ear to test bone conduction.
Audiography provides a more precise measurement of hearing. Air conduction is tested by having you wear earphones attached to the audiometer. Pure tones of controlled intensity are delivered, usually to one ear at a time. You are asked to indicate (by raising a hand, pressing a button, or other means) when they hear a sound, and the minimum intensity (volume) required to hear each tone is graphed. An attachment is placed against the bone behind each ear to test bone conduction.
How to Prepare:
Adults:
There is no special preparation.
Infants and children:
The physical and psychological preparation you can provide for this or any test or procedure depends on your child's age, interests, previous experience, and level of trust. For specific information regarding how you can prepare your child, see the following topics as they correspond to your child's age:
How it Feels:
There is no discomfort. The length of time varies. Screening may take about 5 to 10 minutes; detailed audiography may take about 1 hour.
Risks:
There is no risk.
Why this Test is Performed:
This may be a screening test to detect a hearing loss at an early stage. It may also be used when there is difficulty in hearing from any cause. Common causes of hearing loss include chronic ear infections , a ruptured eardrum , acoustic trauma , an occupational hearing loss , a head injury , inherited conditions, diseases of the inner ear, and complications of ototoxic medications (medications that can be toxic to the nerve of the inner ear, including certain antibiotics such as neomycin, diuretics such as Lasix, and large doses of salicylates such as aspirin).
Normal Values:
The unimpaired ability to hear a whisper, normal speech, and a ticking watch is normal. The unimpaired ability to hear a tuning fork through air and bone is normal.
Audiography screening usually includes 2 tones of 256 cps and 4,096 cps delivered at 5 and 10 dB (the normal speech range). Detailed audiography shows normal hearing, with low tones (around 64 cps) heard at 1 or 2 dB and high tones (11,584 cps) heard at around 10 dB, and tones in between this range all heard at less than 10 dB.
Abnormal Results:
There are many different kinds and extents of hearing loss . Some include only the loss of the ability to hear high or low tones, or the loss of only air or bone conduction. The inability to hear pure tones below 10 dB indicates some extent of hearing loss. The extent and kind of hearing loss may give clues to the cause and the prognosis (probable outcome).
Conditions that may affect test results:
Cost:
A screening audiometry test with only a few tones costs around $10 to $15, and some schools provide this service to children at no cost.
A detailed audiometry test costs about $40 to $50.
Special Considerations:
There are many hearing function tests, from simple screenings (such as producing a loud noise and observing the test subject for a startle response) to complex, detailed measurements such as the auditory evoked responses test (BEAR), in which an electroencephalogram is used to detect brain wave response to sounds.
This is an illustration of the external, middle, and inner ear. The detailed section is of the eardrum and the three tiny bones that conduct sound from the drum to the cochlea.
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