A Pilot Study to Evaluate a Residual Inhibition Technique in Hearing Aids for Suppression of Tinnitus

Tinnitus acoustic therapy is defined as any use of sound where the intent is to alter the tinnitus perception and/or the reactions to tinnitus in a clinically beneficial way. The parameters of sound that may cause beneficial effects, however, are currently only theorized with limited data supporting their effectiveness. Residual inhibition is the temporary suppression or elimination of tinnitus that is usually observed following appropriate auditory stimulation. Our pilot study investigated the effects of a therapeutic acoustic stimulus that was individually customized to maximize residual inhibition of tinnitus and extend its duration to determine if there could be a sustained suppression of the tinnitus signal (i.e., reduced tinnitus loudness) and a reduction in the psychological and emotional reactions to tinnitus. This pilot study had two objectives: (1) to evaluate the feasibility of residual inhibition technique therapy through daily use of hearing aids and (2) to determine its effects by measuring reactionary changes in tinnitus with the Tinnitus Functional Index (TFI) and perceptual changes in tinnitus loudness. A total of 20 adults (14 males, 6 females; mean age: 58 years, SD = 12.88) with chronic tinnitus were enrolled in a four-visit study that consisted of the following: (1) baseline visit and initiation of the intervention period, (2) a 1-month postintervention visit, (3) 2-month postintervention visit and initiation of a wash-out period, and (4) a 3-month visit to assess the wash-out period and any lasting effects of the intervention. The intervention consisted of fitting bilateral hearing aids and creating an individualized residual inhibition stimulus that was streamed via Bluetooth from a smartphone application to the hearing aids. The participants were instructed to wear the hearing aids and stream the residual inhibition stimulus all waking hours for the 2-month intervention period. During the wash-out period, the participants were instructed to use the hearing aids for amplification, but the residual inhibition stimulus was discontinued. At all visits, the participants completed the TFI, study-specific self-report measures to document perceptions of tinnitus, a psychoacoustic test battery consisting of tinnitus loudness and pitch matching, and a residual inhibition test battery consisting of minimum masking and minimum residual inhibition levels. At the end of the trial, participants were interviewed about the study experience and acceptability of the residual inhibition treatment technique. Repeated measures analyses of variance (ANOVA) were conducted on the two main outcomes (TFI total score and tinnitus loudness) across all four visits. The results showed a significant main effect of visit on the TFI total score ( p  < 0.0001). Specifically, the results indicated a significant reduction in TFI total scores from baseline to the 1-month post-intervention period, which remained stable across the 2-month post-intervention period and the wash-out period. The ANOVA results did not show a significant change in tinnitus loudness as a function of visit ( p  = 0.480). The majority of the participants reported a positive experience with the study intervention at their exit interview. This pilot study demonstrated that residual inhibition as a sound therapy for tinnitus, specifically through the daily use of hearing aids, was feasible and acceptable to individuals suffering from chronic tinnitus. In addition, participants showed improvement in reactions to tinnitus as demonstrated by sustained reduction in TFI scores on average over the course of the treatment period. Achieving residual inhibition may also provide patients a feeling of control over their tinnitus, and this may have a synergistic effect in reducing the psychological and emotional distress associated with tinnitus. There was no significant reduction in long-term tinnitus loudness resulting from the residual inhibition treatment; however, the current pilot study may not have had sufficient power to detect such a change. The combination of tinnitus suppression and improved psychosocial/emotional reactions to tinnitus may result in a better quality of life in both the short and long term. A larger-scale study is needed to determine the validity of using residual inhibition as a clinical therapy option and to ascertain any effects on both perception and reactions to tinnitus.