Figure 2

Measurement of hearing function using ABR and DPOAE before and after shock-wave exposure. (a, d) Significant ABR threshold shifts were observed one day after shock-wave exposure (filled red squares) for up to 28 days after exposure (filled green diamonds) at higher frequencies in the LISW group (d) compared to the pre-exposure thresholds (filled circles). Although the thresholds 28 days after exposure at all frequencies were larger than the pre-exposure thresholds, no significant elevation of the ABR threshold was observed in the shock-tube group (a). (b, e) The ABR wave I amplitude was decreased at all frequencies in the shock-tube group, (b) which was also seen in the LISW group, at the same frequencies at which the threshold shift was observed (e). (c, f) A temporal decrease of DPOAE level was observed at 1 day after exposure both in shock tube and LISW group. Although the DPOAE levels 28 days after exposure at higher frequencies were larger compared to the pre-exposure levels, no significant elevation of the DPOAE level was observed at 28 days after both in shock tube and LISW group (g) The ABR threshold shifts (the threshold at 28 days after exposure minus that at pre-exposure) were significantly higher in the shock-tube group at the lower frequencies (5.55–11.33 kHz). (h) The ratio of the wave I amplitude (28 days after exposure to pre-exposure) also decreased in both the shock-tube and LISW groups at all frequencies. Significant differences were observed at the lower frequencies (5.66 and 8.00 kHz). (i) The DPOAE threshold shift between the shock tube and LISW group 28 days after exposure did not differ significantly. The asterisks indicate significant differences (p < 0.05) compared to the pre-exposure values (2-way ANOVA, followed by Bonferroni correction for multiple comparisons). The error bars indicate the SEs of the means (n = 5 in each group). ABR, auditory brainstem response; DPOAE, distortion product otoacoustic emission; LISW, laser-induced shock wave; SE, standard error.