Otoacoustic

Otoacoustic refers to sounds produced by the inner ear, particularly by the cochlea's outer hair cells. Otoacoustic emissions are faint sounds that the ear generates and can be detected in the ear canal with a sensitive microphone. They were first described in the 1970s, with the discovery credited to David Kemp, and have since become a standard tool in audiology.

The mechanism behind otoacoustic emissions involves the active process of outer hair cells, which amplify motion of the basilar membrane. This activity can generate energy that travels back through the middle ear to the ear canal, where it can be recorded. OAEs provide information about cochlear function and can be influenced by the status of the middle ear and the surrounding acoustic environment.

There are several types of otoacoustic emissions. Spontaneous otoacoustic emissions occur without any external stimulus and are not present in all individuals. Evoked otoacoustic emissions require an acoustic probe to deliver sounds and record responses, and include transient evoked OAEs (TEOAEs) and distortion product OAEs (DPOAEs), which are elicited by brief or paired tones respectively.

Applications of OAEs include newborn hearing screening, pediatric and clinical audiology, and monitoring for ototoxicity or noise-induced cochlear changes. They provide a noninvasive, objective measure of outer hair cell function. However, OAEs do not directly assess inner hair cell function or neural pathways, and results can be affected by middle-ear status, noise, and test conditions.