Otoacoustic emissions (OAE) tests are objective electrophysiologic tests that assess cochlear function in response to stimulus and are routinely used as a screening method for newborn hearing impairment. OAEs have high sensitivity but relatively low specificity. A microphone in the ear canal records the sound produced by the outer hair cells in the cochlea, which can be spontaneous, or in response to a stimulus. The test is performed with a speaker and microphone probe in the ear canal. The automated OAEs are used for screening purposes and remove the need for interpretation. Transient-evoked OAEs measure the response to brief clicks at 80–86 decibels. Good responses are expected when hearing thresholds are above 20 dB. The responses are lost above 30 dB, independently of the aetiology of the hearing loss. Distortion product OAEs are tested with two pure tones of different frequency presented simultaneously and for a longer period. The frequencies can be varied to estimate hearing thresholds across the frequencies. One of the limitations of OAEs is that it can miss hearing impairment due to auditory neuropathy. In such patients, the OAEs can be present despite significant hearing impairment and absent or abnormal ABRs.