This project, funded by the National Institutes of Health, is being conducted to learn how structures of the middle-ear and inner ear are affected by age and hearing ability, and to provide a scientific basis for diagnosis and rehabilitation of hearing loss. Volunteers who meet the eligibility requirements may enroll in this study, which will include measurements of hearing using several procedures. Participants 18 years of age and older with normal hearing or hearing loss are currently being recruited. One or two visits of 1.5 to 2 hours are required and scheduling is flexible. Compensation for time will be provided and parking validated.