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Alternative Names Return to top
Audiometry; Hearing test; Audiography (audiogram)Definition Return to top
An audiology exam tests your ability to hear sounds. Sounds vary according to the intensity (volume or loudness) and the tone (the speed of sound wave vibrations).
Hearing occurs when sound waves move to the nerves of the inner ear and then the brain. Sound waves can travel to the inner ear by air conduction (through the ear canal, eardrum, and bones of the middle ear) or bone conduction (through the bones around and behind the ear).
INTENSITY of sound is measured in decibels (dB):
Usually, sounds greater than 85 dB can cause hearing loss in a few hours. Louder sounds can cause immediate pain, and hearing loss can develop in a very short time.
TONE of sound is measured in cycles per second (cps) or Hertz:
The normal range of human hearing is about 20 Hz to 20,000 Hz, and some animals can hear up to about 50,000 Hz.
How the Test is Performed Return to top
The first steps are used to estimate the need for an audiogram. The specific procedures may vary, but they generally involve blocking one ear at a time and checking for the ability to hear whispers, then spoken words or the sound of a ticking watch.
A tuning fork may be used. 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.
Audiometry 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, to one ear at a time. You are asked to raise a hand, press a button, or otherwise indicate when you hear a sound. The minimum intensity (volume) required to hear each tone is graphed. An attachment called a bone oscillator is placed against the bone behind each ear (mastoid bone) to test bone conduction.
How to Prepare for the Test Return to top
No special preparation is needed.
How the Test Will Feel Return to top
There is no discomfort. The length of time varies. An initial screening may take about 5 to 10 minutes. Detailed audiometry may take about 1 hour.
Why the Test is Performed Return to top
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:
Normal Results Return to top
What Abnormal Results Mean Return to top
There are many different kinds and degrees 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 25 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).
The following conditions may affect test results:
Risks Return to top
There is no risk.
Considerations Return to top
There are many different hearing function tests. Simple screenings involve making a loud noise and watching to see if it startles the patient. Detailed screenings include brainstem auditory evoked response testing (BAER). This test uses electroencephalogram to detect brain wave activity when sounds are made.
A newer hearing test called otoacoustic emission testing (OAE) can be used in the very young (such as newborns) or when standard tests do not produce reliable results.
References Return to top
Cummings CW, Flint PW, Haughey BH, et al. Otolaryngology: Head & Neck Surgery. 4th ed. St Louis, Mo; Mosby; 2005:3466-3479.
Kerschner JE. Neonatal hearing screening: To do or not to do. Pediatr Clin North Am. June 2004; 51(3): 725-36, x.
Update Date: 2/19/2007 Updated by: Alden J. Pearl, M.D., Clinical Assistant Professor, Department of Otolaryngology, State University of New York Health Science Center at Brooklyn, Brooklyn, NY. Review provided by VeriMed Healthcare Network.
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Page last updated: 25 September 2008 |