Age-related hearing loss (presbycusis) is a chronic health condition that affects 1/3 of the world’s population. One hallmark of presbycusis is a difficulty hearing in noisy environments. Presbycusis can be separated into two components: alterations of peripheral mechanotransduction of sound in the cochlea, and central alterations of auditory processing areas of the brain. While the effects of the aging cochlea in hearing loss have been well studied, the role of the aging brain in hearing loss is less well understood. Therefore, to examine how age-related central processing changes affect hearing in noisy environments, we used a mouse model (Thy1-GCaMP6s X CBA mice) that has excellent peripheral hearing in old age. We used in vivo 2-photon Ca2+ imaging to measure the responses of neuronal populations in auditory cortex (ACtx) of adult (2-6 months, 9 male, 6 female, 4,180 neurons) and aging (15-17 months, 6 male, 3 female, 1055 neurons) while listening to tones in noisy backgrounds. We found that ACtx neuro...