Influence of Tinnitus on Auditory Spectral, Temporal Resolution, and Speech Perception Ability in Tinnitus Patients

Abstract

Objectives: (1) Evaluate the influence of tinnitus upon the auditory spectral and temporal resolution. (2) Evaluate the effect of tinnitus on speech perception ability in noise. Methods: To exclude the effect of decreased hearing threshold, unilateral idiopathic tinnitus patients with symmetric hearing threshold were enrolled. The subjects were 13 patients with symmetric hearing loss >20 dB HL and binaural difference <10 dB at 0.25, 0.5, 1, 2, 3, 4, and 8 kHz, or who have normal hearing threshold and binaural difference <10 dB at 0.25, 0.5, 1, 2, 3, 4, and 8 kHz, and threshold discrepancies <15 dB at 9, 11.2, 12.5, 14, 16, 18, and 20 kHz. A total of 13 volunteers with normal hearing were enrolled as a control group. Four different psychoacoustic measurements were performed: (1) spectral-ripple discrimination, (2) temporal modulation detection, (3) Schroeder-phase discrimination, and (4) word recognition in noise. Results: There were no significant differences in spectral-ripple threshold, temporal modulation detection threshold, and Schroeder-phase discrimination between affected sides and non-affected sides of unilateral tinnitus patients. For the word in noise test, affected sides showed worse signal-to-noise ratio compared to non-affected side. Conclusions: We could not find any evidence that the tinnitus-affected ears show worse spectral and temporal processing compared with nontinnitus ears in unilateral tinnitus patients. The spectral ripple discrimination data suggests that the tinnitus-affected ear does not have more damage in its cochlea (especially the outer hair cell) causing the auditory filters to broaden compared with the nonaffected ear with the same hearing threshold.