This project, funded by the National Institutes of Health, is being conducted to determine the effects of aging on hearing, understanding speech, and brain functions. This study will provide a scientific basis for diagnosis, rehabilitation and prevention of hearing loss due to aging. Volunteers who meet the eligibility requirements may enroll in this study, which will include measurements of hearing, making listening judgments of sounds, behavioral tasks, questionnaires, and MRI scanning of the brain. Participants 40 years of age and older with normal hearing or hearing loss are currently being recruited. Three visits of 2-3 hours each are required and scheduling is flexible.