This study enrolled patients who visited our out-patient department with the primary complaint of tinnitus. A full medical history assessment was performed, and each patient underwent an otoscopic examination, a basic audiologic evaluation. We selected the patients whose audiogram data met the inclusion criteria for NIHL: 1) bilateral typical NIHL audiogram and type A tympanogram; 2) hearing threshold above 4 kilohertz (kHz) was greater than 25 dB hearing level (HL); 3) audiogram showed the characteristic 4 kHz or 6 kHz notch (average hearing threshold was 10 dB HL higher than the baseline); 4) up-turn phenomenon appeared above 6 kHz or 8 kHz, and 5) symmetrical hearing loss threshold over bilateral ears and the disparity was less than 10 dB HL. Patients with other otologic diseases were excluded.