Distortion product otoacoustic emissions (DPOAEs) are evoked by the simultaneous presentation of two pure-tones or primaries, referred to as f1 and f2. Because the cochlea is non-linear in nature, distortion occurs at various places along the cochlea during stimulus presentation. During a DPOAE test, various pairs of the stimuli are presented to the ear and the largest corresponding distortion product is measured at the frequency expressed as 2f1-f2.

Transient evoked otoacoustic emissions (TEOAEs) are most often evoked using a repeated broadband click stimulus. They are recorded during the brief intervals between the stimulus presentations that activate a wide area of the basilar membrane.

There are many reasons for choosing one OAE test method over the other. Some prefer the TEOAE method when trying to conduct a quick OAE screening on a child while others find DPOAEs more suitable when assessing adult patients. Either way, both methods assess outer hair cell function and provide important information about the status of the cochlea.