What are otoacoustic emissions (OAEs)?

Otoacoustic emissions are sounds that are produced by healthy ears in response to acoustic stimulation.

How are OAEs measured?

OAEs are measured by presenting a series of very brief acoustic stimuli, clicks, to the ear through a probe that is inserted in the outer third of the ear canal. The probe contains a loudspeaker that generates clicks and a microphone that measures the resulting OAEs that are produced in the cochlea and are then reflected back through the middle ear into the outer ear canal. The resulting sound that is picked up by the microphone is digitized and processed by specially designed hardware and software. .

What is the clinical use of OAEs?

OAEs are evidence of a vital sensory process arising in the cochlea. OAEs only occur in a normal cochlea with normal hearing. If there is damage to the outer hair cells producing mild hearing loss, then OAEs are not evoked. A good rule of thumb is that OAEs are present if hearing is 35 dB or better. Because OAEs are evoked by signals that have a wide frequency response, a broad region of the cochlea responds, providing information on the frequency range from 1000 Hz to 4000 Hz.

OAEs were approved by the FDA for clinical use on July 14, 1989. They are most appropriate for use in difficult-to-test patients: newborn infants, young children, and developmentally delayed populations. OAEs only provide information about the activity of the cochlea, and do not assess the status of the auditory pathway, which is tested by the brainstem auditory evoked response (BAER).

A clinical update:

Many states are now requiring all infants to be screened for hearing loss. In fact, the State of North Carolina requires mandatory screening of all infants born in any hospital. The use of OAEs has proved to be a very good screening tool for infants over 24 hours old and will probably be incorporated into most screening programs.