Technical aspects of brainstem evoked potential audiometry using tones.

The brainstem response to brief tones contains a large vertex-positive component. If high-pass filter settings above 20 Hz are used, particularly with high rolloff slopes, the morphology of the response changes so that a vertex-negative wave becomes the most prominent component of the response. The amplitude of the response is unaffected by stimulus presentation rates of up to 35/sec. Tones with longer rise times have greater frequency specificity, but at rise times of greater than 5 msec, the brainstem response becomes very small. At high intensities, regardless of the rise time, the response to tones is not completely frequency specific, and notched noise masking should be used to obtain frequency-specific responses.