Otoacoustic emissions

Otoacoustic emissions are sounds generated by the inner ear and measurable in the ear canal. They arise from active mechanical processes in the cochlea and provide a noninvasive measure of cochlear function.

Cochlear amplifier: An active process in the cochlea that amplifies faint sound-induced vibrations through energy supplied by outer hair cells. Its active gain is the source of the cochlea’s measurable acoustic output.
Otoacoustic emission test: A hearing test that measures sound emitted by the cochlea through a probe placed in the ear canal. It is the direct clinical method for detecting these emissions.
Distortion-product otoacoustic emission: An otoacoustic emission generated when two tones interact nonlinearly in the cochlea. This common test response probes cochlear function at selected frequencies.
David Kemp: A British physicist who demonstrated measurable sounds emitted by the human ear in 1978. His observation established the modern study of otoacoustic emissions.
Outer hair cell: A sensory cell in the cochlea that changes length in response to electrical stimulation and helps amplify sound-driven motion. These cells provide the active force underlying most otoacoustic emissions.
Newborn hearing screening: Routine testing that identifies newborns who may have hearing loss and need further evaluation. Otoacoustic emissions provide a quick, noninvasive screening method.
Transient-evoked otoacoustic emission: An otoacoustic emission elicited by a brief sound such as a click or tone burst. Its response to a broadband transient offers a different measurement from two-tone testing.
Georg von Békésy: A Hungarian-American biophysicist who studied traveling waves in the cochlea and received the 1961 Nobel Prize in Physiology or Medicine. His passive model of cochlear mechanics preceded evidence for active amplification.
Cochlear traveling wave: A wave of motion that travels along the basilar membrane in response to sound. Its interaction with active cochlear mechanics shapes emitted sounds.
Auditory brainstem response: A test that records electrical activity in the auditory nerve and brainstem after sound stimulation. It can assess neural hearing pathways that an emission test does not measure.

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