[No Change Proposed by Supplement Activities] PROJECT SUMMARY/ABSTRACT Adverse auditory environments in indoor spaces present constant challenges to children during everyday learning and social interactions. Spatial hearing provides access to auditory cues that promote auditory and speech perception in these difficult listening situations. However, auditory spatial cues are distorted in most indoor spaces due to reverberation—the excessive sound energy reflected from room surfaces arriving at the listener shortly after the initial sound directly from the source. The perceptual consequences of reverberation on spatial hearing have not been characterized in children with normal hearing, leaving a critical gap in our knowledge of benchmark abilities to assess hearing device fitting outcomes for children with hearing loss during real-world listening. In the proposed work, our goal is to reveal the developmental trajectories of functional spatial hearing abilities under realistic reverberation between 6- to 18-year-old children. This age range reflects the protracted development of perceptual abilities, which underlies a multitude of immaturities in children’s processing of auditory information particularly in difficult listening situations. This work takes an innovative and unprecedented approach to study the impact of reverberation in auditory virtual reality, in which realistic auditory environments mimicking children’s learning environments are simulated to maximize ecological validity. Across the specific aims, we examine three aspects of functional spatial hearing abilities under virtual reverberant environments that vary in interaural coherence—a metric that describes reverberation severity. In Aim 1, we will investigate developmental changes in apparent source width—a measure of perceived auditory object size that is critical for auditory scene analysis. In Aim 2, we will investigate the development of minimum audible angle, the smallest detectable angular separation between two sounds—a well-tested metric for auditory spatial acuity. In Aim 3, we will investigate developmental changes in minimum angular separation—a novel measure of spatial unmasking based on the smallest spatial separation required to receive a target speech benefit in competing babbles. By correlating the three outcome measures from the independent aims, we will assess the inter-relationships between auditory object perception, spatial acuity, and spatial unmasking in reverberant environments among school-aged children. Findings from the proposed work will (i) establish our understanding of typical developmental trajectories of functional spatial hearing in realistic reverberant environments, and (ii) elucidate the role of auditory object perception in spatial acuity and subsequently spatial unmasking in children. Together, this work will provide intervention benchmark to assess fitting outcomes for children with hearing loss, and will generate substantial feasibility and ...