The auditory brainstem response (ABR) is a true neurological potential that that occurs within the brainstem in response to an auditory stimulus. The ABR typically occurs 15 milliseconds after presentation of the stimulus. ABR testing uses averaging to accumulate the tiny ABR response hidden in the noise, displaying the response amplitude from the brainstem over time.
Electrocochleography (ECochG) is a measure of the electrical potentials of the cochlea. Typically, the measurement is characterized by the stimulus onset (baseline), the response of the cochlea to the stimulus (summating potential), and the response to the synchronous firing of nerve fibers (action potential).