Little is known regarding the epidemiology, etiology, pathophysiology, and comorbidities of hearing loss and tinnitus in the military population. The Department of Veterans Affairs (VA) is consequently unable to predict the risk of auditory disorders in Service members exposed to noise. Compounding this problem, many other military and non-military exposures can cause auditory injury, including solvents, blasts and other sources of traumatic brain injury (TBI), and certain other injuries and medical conditions. Non-military (e.g., recreational) or post-military exposures (i.e., Veterans' occupational exposures) may also contribute to long-term risk. It is critical to attain a fundamental understanding of the epidemiology and pathophysiology of tinnitus and hearing loss, as well as their interrelatedness. Such an understanding could help identify individuals at risk for auditory injury, and ultimately lead toward much-needed rehabilitation methods that target the underlying causes. In 2012, in response to recommendations made by the Institute of Medicine (IOM; now the National Academies of Medicine) in their congressionally-mandated report titled, “Noise and Military Service: Implications for Hearing Loss and Tinnitus,” we assembled a team of audiology, epidemiology, and health services researchers at the VA Rehabilitation Research & Development (RR&D) National Center for Rehabilitative Auditory Research (NCRAR) to design a longitudinal study focused on auditory health in recent Veterans. The Noise Outcomes In Service members Epidemiology Study (“NOISE Study”) was funded in 2013 [Congressionally Directed Medical Research Programs (CDMRP) grant #W81XWH-12- PRMRP-IIRA]. The study enrolls Veterans within 2.5 years of military separation, allowing us to measure their military exposures within a reasonable recall period. In 2014, the Department of Defense (DoD) Hearing Center of Excellence (HCE; San Antonio, TX) was added as a second site to increase enrollment and to expand our target population to include active-duty military Service members. Enrollment at the HCE began in June 2015. The present proposal requests funding to continue study activities for the next 4-year period for the NCRAR site. (Should the HCE not receive continuation funding from the DoD, their participants will be followed by the NCRAR team.) Since the NOISE Study's inception, baseline data have been collected on 644 Veterans at the NCRAR and 373 Service members at the HCE (1,017 participants enrolled across the two sites). The baseline examination includes a full audiologic test battery with an extensive survey component. Participants complete annual follow- up surveys (online) to capture ongoing exposures and any changes in health and functioning. The in-person audiologic examination is repeated every 5 years, allowing us to identify changes in auditory function over time and contrast those changes with Veterans' past military exposures and/or ongoing non-military exposures. For...