EFFECTS OF CLICK DURATION ON THE LATENCY OF THE EARLY EVOKED-RESPONSE

The effect of click duration on the latency of waves I, III and V was investigated by testing 20 normal-hearing subjects at 60 dB HL [hearing level] using electric pulses of 25, 50, 100, 200 and 400 .mu.s. Alternating condensation and rarefaction clicks were used. Similar and nonsignificant latency differences were recorded for the 25-, 50- and 100-.mu.s pulses. The 100-.mu.s duration is preferred to the 25-.mu.s pulse because the latter reduced the maximum measurable hearing loss by about 13 dB. Latencies increased .apprx. 0.10 ms as duration increased from 100 to 200 .mu.s and by 0.20 ms when duration increased from 100 to 400 .mu.s. Although such differences by themselves are small, they can combine with other stimulus or recording variables to be clinically significant. It is important to control click duration when normative data are generated. The interaction of polarity (condensation rarefaction and alternating) and pulse duration (100 and 400 .mu.s) on the wave V latency were assessed. There were no latency differences among polarities at either duration.