Evaluation of Masking Effects on Speech Perception in Patients With Unilateral Chronic Tinnitus Using the Hearing in Noise Test

Abstract

To verify that tinnitus itself could disturb speech perception and to evaluate the effects of masking noise on speech perception ability in the patients with normal hearing but unilateral chronic tinnitus using the hearing in noise test. Prospective, nonrandomized study. Between June 2009 and May 2011, we enrolled 20 patients with normal hearing and subjective unilateral tinnitus that had persisted for more than 12 months, along with 20 healthy controls of the same age. All subjects were evaluated using audiologic examinations, the tinnitus handicap inventory, and the Korean version of the Hearing in Noise Test (K-HINT) to assess characteristics of tinnitus and speech perception ability in various noisy situations. Reception threshold for speech (RTS) in a quiet environment and signal-to-noise ratio (SNR) in various conditions of noise were significantly higher in the tinnitus than in the control group, regardless of whether noise came from the front, right, or left (p < 0.05). When the tinnitus group was subdivided according to the site of noise exposure, the mean SNR of the contralateral noise group was -7.9 ± 1.4 dB, which was significantly higher than the ipsilateral noise (-9.1 ± 1.8 dB) or control group (right, -10.0 ± 0.6 dB; left, -10.1 ± 0.5 dB) (p < 0.05). In addition, there was no significant difference between ipsilateral noise and control groups. From this study, we showed that tinnitus itself could adversely affect speech perception ability by increasing both RTS and SNR in the tinnitus patients in comparison with healthy controls. In addition, we suggest that proper level of noise on the site of tinnitus might be helpful to increase speech perception in the patients who experience chronic subjective tinnitus.