At day 7, ABR wave I, III, and V latencies, and I-III, I-V interwave intervals (IWIs) in the experimental group were significantly prolonged compared with those in the control group. ABR thresholds were also elevated in the experimental group. We found no significant difference in DPOAEs in the bilirubin exposure group compared to the control group. The ABRs and DPOAEs in the experimental group were restored at age 28 days. Cochlear hair cells showed no signs of loss in either group; however, the total number of neurofilament-positive cells in SGNs was significantly reduced in the phenylhydrazine-treated animals.