During the mastoid surgery, drilling noise can reach 130 dB SPL and these intensities have been known to produce cochlear hair cell damage. Since this noise damage may begin in the high frequency range, high frequency audiometry is an appropriate tool to assess the acoustic trauma incurred during mastoid surgery. This study was undertaken to measure the degree of high-frequency sensorineural hearing loss following mastoid surgery. Forty patients undergoing mastoidectomy procedures were tested preoperatively, 1 day, 7 days, and at 30 days postoperatively using Belton 2000 high-frequency audiometer. Duration surgical drilling was recorded. There were no significant changes in postoperative hearing threshold. Therefore, there is no influence on contralateral hearing threshold by drilling noise after mastoidectomy.