A review of auditory gain, low-level noise and sound therapy for tinnitus and hyperacusis
Objective: This article reviews: (1) the evidence related to enhanced central gain as a potential mechanism for the generation of tinnitus and hyperacusis, (2) the neuroplastic changes induced by prolonged, low-level sound stimulation and (3) the clinical effectiveness of various sound therapies and amplification for the treatment of tinnitus and hyperacusis. Design: General literature review. Study sample: Peer-reviewed articles related to auditory neural gain, prolonged low-level noise exposure and effectiveness of sound therapy. Results: A large body of literature exists supporting the enhanced neural gain model of tinnitus and hyperacusis. Neuroplastic changes associated with prolonged low-level noise show evidence of reversing enhanced neural gain, which should theoretically reduce percepts of tinnitus and/or hyperacusis. However, the available clinical evidence assessing the efficacy of sound therapy to reduce tinnitus or hyperacusis lacks controlled clinical trials to accurately assess the effectiveness of sound therapy. Conclusions: The available literature from basic science studies supports the neural gain model of tinnitus and hyperacusis, which conceivably should be effectively managed with sound therapy. However, well-controlled clinical trials are needed before conclusions can be made on the effectiveness of sound therapy for tinnitus and hyperacusis.