Bilateral hearing aids: a review of self-reports of benefit in comparison with unilateral fitting

The literature on self-assessed outcomes from bilateral and unilateral hearing aid fitting is reviewed. The nature, aims, and design of different studies are quite varied, and limitations attend many of them. Nonetheless, certain indications can be extracted from the pattern of reported results. Thus, greater measured impairment, greater self-rated disability, and/or more critical contexts of listening emerge as candidate predictors of preference for, or persistence with, a bilateral fitting profile. Two matters are briefly critiqued regarding one vs two hearing aids: 1) the analogue with binocular optical correction; 2) the unaided ear ("deprivation") effect. Questions are raised about the adequacy of the range of hearing functions addressed by previous investigations of bilateral vs. unilateral fitting-and a broadened range of functions is outlined. A recent self-report-based comparison of one versus two hearing aids (Noble & Gatehouse, International Journal of Audiology, 2006) reveals that the benefit of two lies in contexts of more demanding and dynamic listening and in reduced listening effort.