Earspeaker coupling effects on auditory action potential and brainstem responses.

Human auditory nerve action potential and brainstem evoked response input-output functions were obtained with standard audiometric earspeakers coupled in three different ways, commonly used in auditory evoked potential laboratories (ie, free field, circumaural cushions, standard audiometric cushions). All other stimulus values were matched as closely as possible. Under the different coupling conditoins, substantially different amplitude-intensity and latency-intensity functions were generated for both auditory nerve N1 and brainstem V peaks. Differences among the input-output functions were predictable from differences in click frequency spectra.