IMMITTANCE AUDIOMETRY

Immittance audiometry is an objective technique which evaluates middle ear function by three procedures: static immittance, tympanometry, and the measurement of acoustic reflex threshold sensitivity. In this test, a small probe is placed in the ear and the air pressure in the ear canal is varied. This test tells how well the eardrum and other structures in the middle ear are working. In acoustic reflex testing a probe is placed in the ear and a loud tone, greater than 70 dBSPL, is produced. The test measures the reflexive contraction of the stapedius muscle, which is important in protecting the ear from loud noises, such as a person’s own speech which may be 90 dBSPL at the eardrum. This test can be used to estimate the hearing thresholds in patients who are unable to perform normal pure tone audiometry and can also give information about the vestibular and facial nerves and indicate if a lesion may be present.