Tinnitus is the most prevalent service-connected disability for Veterans. Many Veterans are offered sound- based (acoustic) therapy for tinnitus that is intended to alter the tinnitus perception and/or reactions to tinnitus in a clinically beneficial way. Various methods of acoustic therapy are in use and companies are promoting different products. It remains unknown; however, how certain acoustic parameters may be more effective than others. Recent research has shown the benefit of one such acoustic therapy, Notched Noise Therapy, that presents wideband sound with the tinnitus frequency region notched out, theorized to distribute lateral inhibition into the notched frequency region to suppress neural activity believed to cause the tinnitus percept. Previous studies have typically involved brief daily exposures, which are not as likely to remodel neural processes underlying tinnitus as is continuous “immersion” in background sound, which is adopted here. The proposed study will conduct a randomized controlled trial to evaluate the efficacy of notched noise therapy (NNT). The long-term goal of our research program is to develop an accessible, evidence-based treatment that reduces tinnitus loudness and to be able to assess that treatment through a validated method of behavioral and physiological clinical tools. The overall objective for this CDA-2 research plan, which is the next step toward attainment of our long-term goal, is to systematically evaluate the utility of functional, psychoacoustic, and electrophysiologic measures to reveal the overall whole-health impact in Veterans with chronic tinnitus. The trial will enroll 108 participants, who will be randomized to one of three acoustic therapy methods: amplification + notched noise, amplification + noise without notch, and amplification-only. The three groups will be asked to wear ear-level devices (combination instruments that provide both amplification and 1-10 kHz shapeable noise) as much as possible during waking hours. All participants will undergo acoustic therapy for 8 weeks and will complete outcome measures (i.e., Tinnitus Functional Index, Psychoacoustic loudness and pitch matches, AEP, and EEG measures) at baseline and at 4 and 8 weeks. They will repeat outcome assessment at 12 weeks to evaluate for maintenance of any effects while not receiving acoustic therapy for 4 weeks. (Participants requiring hearing aids for hearing loss will continue to use their aids during the 4-week no- treatment period). We hypothesize that NNT suppresses tinnitus perception by distributing lateral inhibition into the notched frequency region and will therefore, reduce the perception of tinnitus loudness. At the completion of this CDA-2 program, the expected outcomes include a NNT as a therapy for tinnitus and the contributions that it may have on tinnitus perception as well as a solid training foundation for a successful VA research career. These results are expected to have an important positive impact ...