Otoacoustic Emissions (OAE)

The normal cochlea produces sound in response to external stimulation; this internally generated sound is the measured response during OAE tests.

To measure OAEs, a small probe is placed in the infant’s ear canal and sound is presented by either one or two tiny loudspeakers. Any response generated by the ear is recorded with a small microphone housed inside the probe.
Signal averaging is used to reduce the level of background noise, which comes primarily from breathing or movement.
If an infant’s cochlea is functioning normally, internally generated sounds will be recorded.

If cochlear hearing loss exists, the cochlea either will not generate a response or it will generate a response that falls below the level that is expected from an ear with normal hearing.

Normal external and middle ear function is important if OAE measurements are to be interpreted correctly as tests of cochlear function. Even if a cochlea is functioning normally and produces an OAE, the response may not be recorded if it is attenuated by fluid in the middle ear or any external ear canal anomalies.

Transient evoked and distortion product OAEs are in the most widespread clinical use. They differ somewhat in the way that they are generated and recorded, but both provide accurate frequency-specific information.