Reflection of bounce phenomenon in TEOAE in humans: dependence upon test-stimulus parameters.

The bounce phenomenon signifies an alteration of hearing after presentation of low-frequency loud tones. Generally, it implies an initial improvement and a following reduction in auditory sensitivity that reaching peaks at 1- and 3-min intervals of the post-exposure time, respectively. The dependence of the bounce upon test-stimulus parameters has been investigated in the present study. Normally hearing subjects were tested and transiently evoked otoacoustic emissions, TEOAEs, were utilized for an objective assessment of the event. Clicks and tone-pips served for test-stimuli, i.e. for TEOAE registrations, while a tone of 250-Hz frequency and of 95-dB SPL intensity has been exposed during 3 min for the bounce initiation. Post-exposure TEOAE changes were more prominent at lower than at higher test-stimulus intensity, 15 vs. 35 dB nHL. The differences concerned both phases of the bounce, augmentations and reductions. On the other hand, under different test-stimulus frequencies, 250, 500, and 2000 Hz, the bounce, particularly augmentations, owned similar magnitudes. It has been concluded thus that the mechanism of the bounce, particularly of its augmentation phase, is global and covers all cochlear regions, tuned to different sound frequencies.