The purpose of this agreement is to provide funding for scientific and technical support as well as quality assurance of two large audiometric examination surveys funded by NIDCD. The two surveys are: The National Health and Nutrition Examination Survey (NHANES) and (ii) Age, Gene/Environment Susceptibility Study?Reykjavik Study (AGES?RS). The Audiometry Components of both the NHANES and AGES?RS were previously developed by NIDCD in collaboration with NIOSH and other consultants. NIOSH collaborated on the design of the experimental protocol and provided the equipment specifications, oversight of maintenance and calibration, technician training and oversight, operations manual development, and quality assurance for the NHANES. As well, NIOSH provided similar support to AGES, including site visits for training and observation, technical assistance, and limited quality assurance. The NHANES scientific goals are to establish a statistically accurate, demographically representative baseline on the general health (including Hearing Health) of the U.S. population. NHANES is now a continuous survey and while general health issues are always under investigation such as height, weight and blood pressure, there are also elements that track individual health outcomes that move in and out of the NHANES as it cycles. NHANES consists of two major components: the household interview and the physical examination in the NHANES Mobile Examination Centers (MECs) that are set up in various areas around the country. The data from the NHANES elements are collected, weighted, and made available to the government and the public as a database on which analysis may be performed. Recently, the data have been released every two years with collaborating agencies receiving the data six months prior to the public release of the data sets. The AGES?RS scientific goals are: 1) to identify genetic and new risk factors for selected diseases including atherosclerosis, cognitive impairment, dementia, stroke, hearing loss, visual impairment, sarcopenia, osteoporosis, and obesity, 2) to characterize phenotypes for these diseases and conditions, and 3) to identify contributory molecular markers associated with these conditions. Both AGES?RS and NHANES share a similar hearing component, developed collaboratively by NIDCD, NIOSH, NCHS, and the Icelandic Heart Association Research Institute. The hearing component consists of: 1) a set of questionnaires relating to hearing, noise exposure, and other factors relating to hearing, and 2) audiometric examinations consisting of otoscopy, acoustic immittance (bilateral tympanometry and screening for ipsilateral acoustic reflexes at 1000 and 2000 Hz), and pure-tone, air-conduction audiometry to determine the hearing thresholds in each ear at 500, 1000, 2000, 3000, 4000, 6000, and 8000 Hz. A repeat threshold test is obtained at 1000 Hz as a measure of test reliability. When significant inter-ear differences are found, then retests are performed using insert earphones to maximize the inter-aural attenuation rather than using a noise masker of the non-test ear to obtain what is referred to as masked threshold in the in the test ear, thus avoiding a ?shadow audiogram? from the better non-test ear.