Audiology

• Alternative Names

  Audiometry; Hearing test; Audiography (audiogram)

• How the test is performed

  The first steps are to see whether you need an audiogram. The specific procedures may vary, but they generally involve blocking one ear at a time and checking your ability to hear whispers, 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. To test air conduction, 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

  No special preparation is needed.

• How the test will feel

  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

  This test can detect hearing loss at an early stage. It may also be used when you have difficulty hearing from any cause.

  Common causes of hearing loss include:

  • Acoustic trauma
  • Chronic ear infections
  • Diseases of the inner ear
  • Head injury
  • Inherited conditions
  • Medications that can be toxic to the nerve of the inner ear, including certain antibiotics (such as neomycin), diuretics, and large doses of salicylates (such as aspirin)
  • Occupational hearing loss
  • Ruptured eardrum
• Normal Values
  • The ability to hear a whisper, normal speech, and a ticking watch is normal.
  • The ability to hear a tuning fork through air and bone is normal.
  • In detailed audiometry, hearing is normal if you can hear tones from 250 Hz - 8,000 Hz at 25 dB or lower.
• What abnormal results mean

  There are many different kinds and degrees of hearing loss. In some types, you only lose the ability to hear high or low tones, or you lose only air or bone conduction. The inability to hear pure tones below 25 dB indicates some hearing loss.

  The amount and type of hearing loss may give clues to the cause and outlook.

  The following conditions may affect test results:

  • Acoustic neuroma
  • Acoustic trauma
  • Age-related hearing loss
  • Alport syndrome
  • Labyrinthitis
  • Meniere's disease
  • Occupational hearing loss
  • Otosclerosis
  • Ruptured or perforated eardrum
• What the risks are

  There is no risk.

• Special considerations

  There are many different hearing function tests. In simple screenings, the health care provider will make a loud noise and watch to see if it startles you. Detailed screenings include brainstem auditory evoked response testing (BAER). This test uses an electroencephalogram to detect brain wave activity when sounds are made.

  A newer hearing test called otoacoustic emission testing (OAE) can be used in very young children (such as newborns) or when standard tests do not produce reliable results.

• References

  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.

Review Date: 10/10/2008

Reviewed By: Alan Lipkin, MD, Otolaryngologist, Private Practice, Denver, Colorado. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.