How aging and noise exposure interact to produce hearing loss is an important issue for understanding its etiology. The relationship between age-related hearing loss (AHL) and noise-induced hearing loss (NIHL) is not always additive. Studies using mammalian models suggest that sensitivity to acoustic trauma may be greatest during the extremes of ontogeny - that is, in developing animals and in senescent animals. Zebrafish (Danio redo) have become a popular vertebrate model for examining embryogenesis and genetic defects because there is considerable synteny between zebrafish and human genes. Thus zebrafish mutations that affect ear development, or interact with age to affect hearing, may shed light on similar pathologies in humans. Although age-related shifts in hearing has been examined in developing fishes, the effects of degeneration due to senescence have not been examined in zebrafish or any other teleost. In order to fully understand the effects of inner ear genetic mutations and NIHL in the zebrafish model, baseline data of age-related shifts in hearing capabilities in wild type zebrafish are needed. The purposes of the proposed research will be to 1) examine shifts in hearing capabilities with age and 2) determine how aging (AHL) and noise exposure (NIHL) interact to cause hearing loss in zebrafish. To fulfill these goals, zebrafish will be exposed to specific sound exposures at various ages, and then pathology of the inner ear (via SEM) and hearing thresholds (via auditory brainstem response) will be examined.