Human offset auditory brainstem response: effects of stimulus acoustic ringing and rise-fall time

Offset auditory brainstem response (ABR) traditionally has been thought to be an artifactual response elicited by stimulus acoustic ringing. Additionally, offset ABR's sensitivity to stimulus rise-fall time has been associated with concurrent changes in acoustic ringing. The present study tested the validity of offset ABR by recording the response in 40 young, normal-hearing adults using tone burst stimuli with varying degrees of acoustic ringing and various rise-fall times. Stimuli were computer-generated 10-ms tone bursts of 500 and 2000 Hz. In Experiment 1, offset ABR was recorded using stimuli with no acoustic ringing, normal ringing, and excessive ringing. Rise-fall time was held constant at 0.5 ms. In Experiment 2, rise-fall time was manipulated in a stimulus with no ringing. In Experiment 3, only rise time was manipulated in a no-ringing stimulus, while fall time was held constant at 0.5 ms. Reliable offset ABRs were recorded for all degrees of acoustic ringing, including the "no-ringing' condition. Offset ABR was sensitive to rise and fall times, and was elicited best with a 500-Hz stimulus. The results indicate that offset ABR is a real response and not an artifact produced by acoustic ringing.