Project Summary/Abstract Distortion product otoacoustic emissions (DPOAE) are grossly underutilized in clinical applications. Yet the need for early and accurate diagnosis as well as monitoring of new therapies is growing and will demand more precise diagnostic tools. This proposal lays the foundation for assimilating advanced DPOAE diagnostics into clinical practice. Specifically, the first aim will validate the test performance of a new protocol for recording DP-Grams. This protocol will use frequency-specific stimulus conditions that are matched to local properties of the cochlea with the goal of better detection of mild-to-moderate hearing loss. The second aim will utilize DPOAE growth functions to detect early changes in the cochlea due to aging and differentiate these effects from those induced by over-exposure to noise. The third aim will use an innovative expansion of DPOAEs to objectively estimate cochlear tuning. The proposal will create a two-dimensional joint metric of tuning and DPOAE strength, which will help to identify hearing-related declines beyond mere changes in sensitivity. The proposed work also serves the critical need to extend the frequency bandwidth of all DPOAE applications to the highest frequencies of human hearing. This is made possible by incorporating modern calibration and signal delivery/recording techniques – developed in part by the laboratories of both PIs – into all experiments. The proposed experiments are built on previous peer-reviewed and published work from the two participating laboratories. Taken together, the proposed experiments are critical next steps necessary to move DPOAEs from a screening tool to potent clinical probe that serves the next generation of diagnostic and monitoring needs.