Otoacoustic emission (OAE) testing evaluates the outer hair cells of the cochlea within the inner ear. In a normal cochlea, when sound is introduced into the ear, active processing and amplification of sound that occurs within the cochlea results in very soft sounds that are emitted from the cochlea back through the middle ear space and the eardrum into the ear canal where they can be measured with a sensitive microphone. The presence or absence of these sounds as well as the volume or level of the sounds recorded can provide information about the function or health of the outer hair cells. OAE test results can help determine if hearing loss measured by basic hearing testing is due to changes in the function of the cochlea. OAE testing can also monitor very small changes in outer hair cell function that may occur from exposure to excessive levels of noise or drugs that are toxic to the ear. OAE testing can show changes in cochlear function before those changes are seen with basic hearing testing thus allowing for adjustment in medications. Changes in OAE test results can also signal the need for the use of hearing protection in noise, as well as provide feedback regarding the effectiveness of hearing protection that is currently being utilized.
OAE testing is painless and brief. A soft plastic probe is placed in the external ear canal and sounds, such as tones or clicks, are introduced into the ear. The sounds are not excessively loud and no response is required from the patient. The only requirement is that the patient sits quietly without moving in a comfortable chair during the test.