Conventional versus notch filter amplification for the treatment of tinnitus in adults with mild-to-moderate hearing loss

Introduction: Conventional hearing aids are commonly recommended for the treatment of tinnitus, though results of studies investigating the efficacy of hearing aid-based tinnitus treatments have been mixed. Recently, it has been suggested that the addition of a notch filter around the tinnitus frequency might enhance lateral inhibitory mechanisms and thereby improve tinnitus severity relative to traditional processing. The primary aim of this study was to compare the effects of conventional versus notch filter amplification strategies on subjective tinnitus severity in adults with mild-to-moderate hearing loss and no previous hearing aid experience.

Methods: Thirty-nine adults (mean age=53.6 years; SD=9.7 years) with bilateral, mild to moderate sensorineural hearing loss and an established clinical history of stable, tonal tinnitus participated in this double-blinded study. Each participant was randomly assigned to complete a 12-week hearing aid trial using either a conventional amplification strategy or a strategy which applied a notch filter at the given participant's tinnitus pitch match frequency. Tinnitus-related handicap and distress were assessed before and after the hearing aid trial via the Tinnitus Handicap Inventory (Newman et al., 1996) and the Tinnitus Questionnaire (Hallam et al., 1988).

Results: Average tinnitus severity did not differ significantly between the conventional and notch filter amplification groups following treatment. Moreover, average pre- to post-intervention change scores were relatively low for both groups, indicating minimal effect of either treatment on tinnitus symptoms. Participant age, high-frequency pure-tone average hearing threshold, average daily hearing aid usage, and pre-intervention tinnitus severity ratings were not predictive of treatment success or failure.

Discussion: Results of the present study suggest no significant effect of either conventional or notch filter amplification on average ratings of tinnitus severity following a 12-week hearing aid trial. However, as clinically meaningful changes in tinnitus severity were identified for some participants, future work is needed to better identify those individuals most likely to benefit, as well as optimal amplification characteristics.