Figure 6: ABR measurements. ABR threshold shifts at different frequencies of the present 14-day groups (dark gray) and the present single groups (light gray). A threshold shift was seen in the 14-day group-double compared to the corresponding single group in all measured frequencies (dark gray) and statistically significant at 8 kHz (P = 0.045), 12 kHz (P = 0.013), and 20 kHz (P = 0.04). No big changes in ABR thresholds were seen in the 14-day group-single compared to the 7-day group-single (light gray). Either the recovery at 4 kHz (P = 0.923), 8 kHz (P = 0.665), and 12 kHz (P = 0.235) or the worsening at 16 kHz (P = 0.855) and 20 kHz (P = 0.904) had statistical significance. Data from earlier investigations of our group. ABR = auditory brainstem recording.