The frequency specificity of tone-pip evoked auditory brain stem responses

Auditory brain stem responses were elicited by unfiltered clicks as well as 500-Hz and 1000-Hz tone-pips with and without high-pass noise masking, from normal hearing subjects and from patients with high-frequency hearing losses. The responses elicited by tone-pips were similar in configuration to the familiar click-evoked responses. When presented in quiet, the latencies of responses elicited by tone-pips (i.e. wave V latency) were identical, or close to those evoked by clicks, suggesting common origins on the basilar membrane. With the addition of high-pass filtered white noise mixed with the tone-pips, wave V latency shifted, suggesting responses originating from apical low-frequency regions. This procedure yielded a good approximation of audiograms obtained from the same subjects. The unfiltered clicks inferred hearing sensitivity in the 2000 to 4000 Hz range, the masked tone-pips closely reproduced thresholds at 500 Hz and 1000 Hz.