Prelude: noise-induced tinnitus and hearing loss in the military

Hearing is critical to the performance of military personnel and is integral to the rapid and accurate processing of speech information. Thus, noise-induced hearing loss (NIHL) represents a severe impairment that reduces military effectiveness, safety, and quality of life. With the high levels of noise to which military personnel are exposed and the limited protection afforded by hearing conservation programs, it should be no surprise that annual Veterans Affairs disability payments for tinnitus and hearing loss exceeded $1.2 billion for 2009 and continue to increase. Military personnel work in high-noise environments, yet the Department of Defense (DoD) cannot predict who is susceptible to noise-induced hearing loss and tinnitus. Of those exposed to noise, 80% may also suffer from chronic tinnitus. Despite its prevalence, there are no means to objectively measure the severity of tinnitus in those individuals. A fundamental understanding of the underlying mechanisms of tinnitus and its relation to noise-induced hearing loss is critical. Such an understanding may provide insight to who is at risk for each condition, allow aggressive hearing protection measures in those individuals most at risk, and create areas for treatment for those already suffering from the conditions. The current review will address the scope of the problems of NIHL and tinnitus for the military, discuss the noise environments in which military personnel operate, describe the hearing conservation measures currently in place, and the challenges those programs face. Some recent breakthroughs in NIHL research will be discussed along with some challenges and directions for future research on NIHL and tinnitus.