Glossary

Auditory brainstem response☆

also: ABR, BSER, AABR, automated ABR

An electrophysiological test of the neural auditory pathway from the eighth nerve through the brainstem. It is the essential cross-check for the OAE, which is pre-neural.

See also: Auditory neuropathy spectrum disorder, Cross-check principle, Otoacoustic emission

Auditory neuropathy spectrum disorder☆

also: ANSD, auditory neuropathy, auditory dyssynchrony

A hearing disorder in which the outer hair cells function — so otoacoustic emissions are present — but neural transmission is impaired, giving an abnormal ABR. The signature dissociation that an OAE alone cannot detect.

See also: Otoacoustic emission, Auditory brainstem response, Cross-check principle

Cochlear amplifier☆

also: active process

The active mechanism by which outer hair cells boost low-level sounds and sharpen frequency tuning, feeding mechanical energy back into the travelling wave on a cycle-by-cycle basis.

See also: Outer hair cell, Prestin, Travelling wave, Otoacoustic emission

Conductive hearing loss☆

also: conductive loss, middle-ear hearing loss

A hearing loss caused by impaired sound transmission through the outer or middle ear. It can abolish an otoacoustic emission even when the cochlea is healthy.

See also: Tympanometry, Otoacoustic emission

Cross-check principle☆

also: Jerger-Hayes principle

The principle that the result of any single test must be confirmed by an independent measure before it drives a diagnosis. For the OAE, the cross-checks are tympanometry and the ABR.

See also: Auditory brainstem response, Tympanometry

Distortion-product otoacoustic emission☆

also: DPOAE, distortion product

An otoacoustic emission evoked by two simultaneous pure tones, the primaries f1 and f2. The largest human distortion product appears at the frequency 2f1 − f2.

See also: Otoacoustic emission, Transient-evoked otoacoustic emission, Primaries, Distortion-source emission

Distortion-source emission☆

also: wave-fixed source, nonlinear distortion

An emission generated where the traveling waves of the stimulus tones overlap and the cochlear response saturates. The DPOAE is partly a distortion-source emission.

See also: Reflection-source emission, Distortion-product otoacoustic emission, Dual-source model

DP-gram☆

also: DPgram, distortion-product audiogram

A plot of DPOAE emission level against f2 test frequency, shown alongside the noise floor. The standard way of displaying a DPOAE result.

See also: Distortion-product otoacoustic emission, Signal-to-noise ratio

Dual-source model☆

also: Shera-Guinan taxonomy, two-mechanism model

The framework in which evoked emissions arise by two fundamentally different intracochlear mechanisms — nonlinear distortion and linear coherent reflection.

See also: Reflection-source emission, Distortion-source emission

Early hearing detection and intervention☆

also: EHDI, 1-3-6, universal newborn hearing screening, UNHS

The programme of screening every newborn's hearing, organised around the 1-3-6 benchmark: screen by one month, diagnose by three, intervene by six.

See also: Auditory brainstem response, Otoacoustic emission

Inner hair cell☆

also: IHC, inner hair cells

The sensory cell of the cochlea that transmits the hearing signal to the auditory nerve. Inner hair cells do not generate otoacoustic emissions.

See also: Outer hair cell, Auditory neuropathy spectrum disorder

Medial olivocochlear system☆

also: MOC, efferent system, olivocochlear bundle

The efferent pathway projecting from the brainstem onto the outer hair cells. Its activation reduces outer hair cell gain and measurably suppresses emission amplitude.

See also: Outer hair cell, Cochlear amplifier

Noise floor☆

also: background noise level

The level of background noise in the recording, from the room, the patient, and the instrument. The emission must rise above it to be detected.

See also: Signal-to-noise ratio

Otoacoustic emission☆

also: OAE, cochlear echo, Kemp echo

A low-level sound generated within the cochlea, transmitted out through the middle ear, and recorded with a sensitive microphone in the ear canal. Its presence is a marker of healthy outer hair cell function.

See also: Outer hair cell, Transient-evoked otoacoustic emission, Distortion-product otoacoustic emission, Spontaneous otoacoustic emission

Outer hair cell☆

also: OHC, outer hair cells

The sensory cell of the cochlea that acts as a biological amplifier. Its electromotile length change feeds energy back into the travelling wave; the by-product of that activity is the otoacoustic emission.

See also: Cochlear amplifier, Prestin, Inner hair cell, Otoacoustic emission

Pass / refer☆

also: pass-refer, screening outcome

The two-outcome result of a screening test. A pass means the emission met criterion; a refer means it did not — which is not a diagnosis, only a signal to look closer.

See also: Signal-to-noise ratio, Early hearing detection and intervention

Prestin☆

also: motor protein

The motor protein in the lateral wall of the outer hair cell that drives its voltage-dependent length change — the molecular basis of electromotility.

See also: Outer hair cell, Cochlear amplifier

Primaries☆

also: f1 and f2, primary tones

The two pure tones used to evoke a DPOAE. The lower is f1 and the higher is f2; routine protocols use an f2/f1 ratio of about 1.22 and levels around 65/55 dB SPL.

See also: Distortion-product otoacoustic emission

Reflection-source emission☆

also: place-fixed source, linear reflection

An emission generated by coherent backscatter of the travelling wave off fixed micromechanical irregularities of the cochlear partition. TEOAEs behave predominantly as reflection-source emissions.

See also: Distortion-source emission, Transient-evoked otoacoustic emission, Dual-source model

Reproducibility☆

also: waveform reproducibility, A-B correlation

The correlation between two independently averaged response buffers. A high reproducibility percentage indicates the recorded response is genuine rather than noise.

See also: Signal-to-noise ratio

Signal-to-noise ratio☆

also: SNR, OAE-to-noise ratio

The margin by which the emission exceeds the noise floor. A response is judged present when the SNR meets a criterion value and the response is reproducible.

See also: Noise floor, Reproducibility

Spontaneous otoacoustic emission☆

also: SOAE, spontaneous emission

A faint, continuous tone produced by the cochlea with no external stimulus. A normal finding in many healthy ears.

See also: Otoacoustic emission, Transient-evoked otoacoustic emission

Stimulus-frequency otoacoustic emission☆

also: SFOAE

An otoacoustic emission evoked by a single sustained pure tone. Difficult to separate from the stimulus itself, so it sees little routine clinical use.

See also: Otoacoustic emission, Reflection-source emission

Tonotopy☆

also: tonotopic organisation, place coding

The orderly frequency map of the cochlea: the stiff basal end responds to high frequencies and the floppy apical end to low frequencies.

See also: Travelling wave

Transient-evoked otoacoustic emission☆

also: TEOAE, click-evoked OAE, CEOAE

An otoacoustic emission evoked by a brief broadband click and recorded in the milliseconds that follow. One of the two emissions used routinely in the clinic.

See also: Otoacoustic emission, Distortion-product otoacoustic emission, Reflection-source emission

Travelling wave☆

also: traveling wave, basilar membrane wave

The wave of displacement that moves along the basilar membrane in response to sound, peaking at a frequency-specific place — high frequencies at the base, low frequencies at the apex.

See also: Cochlear amplifier, Tonotopy

Tympanometry☆

also: immittance, impedance audiometry

A test of middle-ear function. It is the cross-check that settles whether an absent emission reflects the cochlea or a conductive middle-ear problem.

See also: Cross-check principle, Conductive hearing loss

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