[Effects of short-term tone exposure on DPOAEs]

Test parameter combinations are known to affect DPOAE measurement. The present study was attempted to find out if different test parameter combinations affect DPOAEs' utility in reflecting the change of cochlear function. Pure tones of moderate intensity (82 dB SPL) and short duration (3 min) were introduced into rabbit's ear canal to cause temporary change of cochlear mechanics, and the change of amplitude of 2f1-f2 DPOAE representing 10 kHz over 10 minutes after the exposure was monitored using equal- and different primary level combinations. It was found that, under the same exposure condition, 2f1-f2 DPOAEs induced by primaries of different levels (L2 = L1 - 12 dB) had showed more initial reduction in amplitude and slower recovery than that induced by primaries of equal levels (L1 = L2). The difference may indicate that there are multiple physiological processes that contribute to the generation of 2f1-f2 DPOAE and that change of DPOAE test parameters may selectively reveal different DPOAE generating processes.