The characteristics of Audioscan and DPOAE measures in tinnitus patients with normal hearing thresholds

Objectives: To investigate auditory dysfunction in patients with tinnitus and normal hearing thresholds using two sensitive audiological measures. Design: The study was designed to investigate the characteristics of Audioscan and DPOAE tests in tinnitus patients with normal hearing thresholds. Audioscan and DPOAE notches were analysed and compared. All tests were performed in a sound-treated chamber or in a sound-treated room. Study sample: Forty-five tinnitus patients with normal hearing thresholds were examined following a written clinical protocol. Results: The averaged hearing levels obtained from tinnitus participants were significantly worse at high frequencies than those derived from the normative data. There was a significantly higher prevalence of Audioscan and DPOAE notches, whose central frequencies matched tinnitus frequencies in the mid-frequency regions, but not in the low-and high-frequency regions. A significant correlation was found between the centre frequencies of the Audioscan notches and the DPOAE notches from 500 to 4000 Hz. Conclusion: Tinnitus in different frequency regions may be associated with different underlying mechanisms of tinnitus generation. Some negative results on the Audioscan and DPOAE notches matching tinnitus pitches may be due to a limited set of discrete frequencies used for the tinnitus pitch matching test.