Reflection of bounce phenomenon in TEOAE in humans: dependence upon exposure parameters

The bounce phenomenon is an alteration of hearing acuity after presentation of loud tones. Generally, it implies the improvement in hearing acuity that followed by the worsening. The dependence of the bounce upon exposure stimulus parameters has been evaluated in the present study. Normally hearing subjects were investigated, while transiently evoked otoacoustic emission, TEOAE, has been recorded to estimate the event objectively. In the 1st experiment, the bounce indices have been compared under different intensities, 55-100 dB SPL, of exposure-tone of 250-Hz frequency. At lower intensities, 65-75 dB SPL, the augmentation phase in TEOAE bounce reflections exceeded the depression one. At higher intensities, 80-95 dB SPL, both phases of the bounce were of similar magnitudes. The event appeared thus bipolar and symmetric. At the highest intensity, 100 dB SPL, TEOAE drop has hardly been preceded by any augmentation. In the 2nd experiment, the bounce manifestations have been compared under different exposure-tone frequencies, 250, 500, and 2000 Hz. Under 250- and 500-Hz frequencies, the bounce was of similar magnitudes. Under 2000-Hz frequency, a conventional bounce has not been seen, a trend to the overall TEOAE decrement being observed only. The bounce mechanism is discussed and its complex rather than simple nature is considered.