Subjects- Human subjects will be recruited for this study who have had a hearing evaluation from the VA Audiology Service at the Portland VA Medical Center and the H. Quillen VA Medical Center. These subjects will respond to flyers or be contacted from an IRB-approved human subject volunteer registry. Additional details regarding recruitment and selection criteria may be found in the next sections of the protocol. The investigators will recruit approximately equal numbers of subjects, with a total of 640. Data will be acquired at the two sites from a total of 190 adult subjects with normal hearing and 180 adult subjects with sensorineural hearing loss. These subjects will be recruited from three age groups: 20-39 years, 40-59 years and 60-79 years for age comparisons of normative middle-ear data. Data will also be acquired at both sites from 250 adult subjects with middle-ear disorders and/or conductive hearing loss from ages 20-89 years. Of this latter group, the investigators plan to enroll 50 subjects with tympanic membrane perforation, 50 subjects with serous otitis media, 50 subjects with cholesteatoma, 50 subjects with otosclerosis, and 50 subjects with unspecified middle-ear disorders. The investigators expect that approximately 20 subjects (from all groups, normal hearing, sensorineural hearing loss, and middle-ear disorders) will be lost as screen failures or will drop from the study, and thus, the investigators will recruit an additional 20 subjects to replace these. This brings the total planned number of subjects recruited for study to 640.