Children attending center-based child care are daily exposed to high noise levels. Associations between noise levels, noise variability, caregiving quality and child well-being were investigated in centers (N = 64) involving children up to four years (N = 245; [mean] = 34.50 months). We examined minimum and maximum levels of noise and noise variability for optimal child well-being. Nonlinear regression analysis confirmed the threshold hypothesis: optimal child well-being was observed for noise levels over 60 dbA and below 65 dbA, and for noise variability over 6.69 dbA and below 7.44 dbA. Linear multilevel regression analysis showed that more hours in care, higher child age and higher general child care quality were related to higher levels of well-being. Noise, a major aspect of environmental chaos, has adverse outcomes on child wellbeing in center child care. The regulation of noise levels in child care centers is needed to provide optimal child well-being. (author abstract)