OAEs

Otoacoustic emissions (OAEs) are sounds generated by the cochlea, specifically by the outer hair cells, that can be measured in the ear canal with a sensitive microphone. In a healthy ear, outer hair cells amplify and refine sound, and in the process emit a small amount of energy back through the tympanic membrane into the ear canal, where it can be recorded.

There are spontaneous OAEs (SOAEs) that occur without external stimulation and evoked OAEs (EOAEs) that are elicited by acoustic stimuli. EOAEs include transient-evoked OAEs (TEOAEs), produced by brief stimuli such as clicks or tone bursts, and distortion-product OAEs (DPOAEs), produced by two continuous tones (f1 and f2) that interact within the cochlea to generate a distortion product (often at 2f1−f2).

Measurement uses an ear probe containing a microphone and loudspeakers. The probe delivers stimuli and records the resulting emissions, which are analyzed to assess cochlear function. In newborn hearing screening, a pass result generally indicates intact outer hair cell function across the tested frequencies and is used to identify ears that may need further testing.

OAEs reflect peripheral cochlear status and do not assess auditory nerve or central pathways. They are influenced by middle-ear status, probe fit, and ambient conditions; conductive hearing loss or middle-ear effusion can reduce or abolish emissions. OAEs are widely used in newborn screening, pediatric and clinical audiology, and in monitoring cochlear status during ototoxic treatments or other exposures. Limitations include that the presence of OAEs does not guarantee normal hearing across all frequencies or in challenging listening conditions.