This project studies changes in cochlear function throughout the human lifespan, defining the timeline for these age-related shifts and the mechanisms driving the changes. We use primarily otoacaoustic emissions, a noninvasive probe of cochlear mechanics to learn about the human peripheral system. We apply both distortion- (DPOAE) and reflection-source (stimulus frequency OAEs and the reflection-component of the DPOAE) emissions using custom-algorithms, innovative swept-tone methodology and advanced analysis schemes. We disentangle the origin of age-related effects by separating distortion product OAEs into their dual components, distortion and reflection; and studying how each component’s phase and amplitude is impacted throughout the human lifespan. In our lab it is important to study both apical and basal halves of the cochlea to yield a more comprehensive understanding of mechanics. The apex has been minimally studied in humans, and wholly unexplored during maturation. Yet, we have recently reported striking immaturities in DPOAE phase for low-frequency signals coded in the apex of neonates. Our exploration of human cochlear function from base to apex using multiple OAE sources establishes a normative framework, provides detailed information about how the newborn cochlea works and how the elderly cochlea ages. This information contributes to more comprehensive cochlear models and toward the development of more innovative probes of cochlear mechanics for human application. This project has been conducted in past years with creative contributions from Dr. Doug Keefe and especially, Dr. Sumit Dhar. At present, Dr. Christopher Shera is collaborating on this project .