Hearing loss and tinnitus are the two most common service-related disabilities among Veterans. These two conditions, together with the progressive effects associated with aging, present an important challenge for effective Veteran care. Furthermore, treatment of tinnitus and hearing loss has been shown to improve quality of life. Auditory rehabilitation for hearing loss commonly includes hearing aids as a means to improve audibility and allow access to important cues for accurate speech perception, which, in turn, promotes successful communication and engagement in psychosocial aspects of life. Hearing aids have also been found to reduce the bothersome ratings of those with tinnitus; in fact, some clinicians routinely fit hearing aids as a primary means of tinnitus treatment, in some cases even when hearing thresholds are within the normal range. In addition to the immediate audibility changes and treatment qualities related to acoustic modification made by the hearing aid, amplification also has the potential to affect higher level auditory processing abilities, such as speech perception in noise, cognition or other abilities required for complex listening tasks the effects (e.g., effort). Long-term effects of amplification, also known as acclimatization effects, are not well understood relative to more immediate audibility-related effects. A better understanding of the long-term acclimatization effects, together with more immediate audibility effects, will help audiologist to improve hearing aid success and benefit among Veterans. An approach using psychophysical, physiological, cognitive, and questionnaire outcome measures of both immediate audibility and long-term acclimatization effects that are associated with hearing aid use may help to clarify the positive impacts of amplification as a rehabilitation approach. The purpose of this study is to examine the way in which immediate audibility effects and long-term auditory processing effects of amplification affect a range of outcome measures. Improved measurement of the changes that occur with amplification will then help to understand and improve rehabilitation success.