Otoacoustic Emissions are faint sounds - best described as “echoes” - produced by the hair cells of the inner ear (the cochlea) in response to stimuli. OAEs are not a test of hearing, but are used as a tool to determine cochlear function. OAE recordings are electrophysiologic and are not dependent on patient response. A probe is placed into the opening of the ear canal for approximately 20 seconds while the patient listens to sounds, like notes on a scale for DPOAEs, or soft clicks for TEOAEs. By measuring the emisssions, audiologists can quickly determine the status of the cochlea, most notably the functionality of the outer hair cells.