목적: Pathophysiology of tinnitus has not been precisely established until now. “Hidden hearing loss” with cochlear synaptopathy(CS) was suggested as a potential pathophysiology of tinnitus with normal hearing threshold. Several studies have demonstrated that subjects with tinnitus and normal audiograms show significantly reduced auditory brainstem response (ABR) wave I amplitudes compared with control subjects, but normal or increased wave V amplitudes, suggesting increased central auditory gain. To our knowledge, little studies of ABR change along duration of tinnitus have been reported. We aimed to research about the “hidden hearing loss” theory along the duration. 방법:In the current study, 84 subjects (31 males, 53 females) who had unilateral tinnitus with normal hearing were included between Jan. 2016 and Oct. 2017. The amplitude of wave I and V, The latency of wave I, III, V were checked at 90dB nHL. Inter-peak latency (IPL) was calculated between wave I and III, wave I and V, wave III and V, respectively. The ratio of amplitude of wave V and I was calculated also. Those data was compared between Tinnitus ear(TEs, Ipsi-lesion) and Non-tinnitus ear(NTEs, Contra-lesion). 결과:The within-subject comparison between TEs and NTEs showed no significant differences in amplitude of wave I and wave V, wave V/I ratio, or latency of wave I, III, V, and IPLs along the duration(acute, subacute, chronic). All other data were not statistically significant, but latency of wave III of TEs are longer than NTEs in acute group. 결론:Our ABR data represent do not meaningful evidence supporting the hypothesis of cochlear synaptopathy with increased central gain in tinnitus subjects with normal audiograms. More subjects are needed.