"A considerable amount of research has documented the effects of noise on elementary school_aged children's cognitive performance and motivation. However, although the preschool years are critical in terms of cognitive development, very little research has been done with this age group. In addition. research on the effects of noise is often done in large metropolitan areas where the noise source is external to the home or school, i.e., road traffic, train traffic, airplane traffic. Noise levels, ho ever. can also be excessive due to design features, i.e., room adjacencies, ceiling heights, too many hard surfaces. In this study preschool_aged children were evaluated on measures of cognitive performance. All of the children attended a child care center in a small town away from any major external noise sources. Due to the design of the classrooms and center, the "internal" noise levels were substantial, approaching decibel levels found in classrooms adjacent to busy airports. A cohort model was used to evaluate changes in cognitive processes before and after major sound attenuation renovation at the child care center. A total of 90, 4 and 5 year old children participated. Children were evaluated on a standardized index of reading readiness. Children were also evaluated by their classroom teacher on language skills utilizing a standardized scale. Approximately half of the children were tested in the first year of the study in the noisy condition. The other half were tested after the renovations were made to reduce noise levels. Family income and parents' educational levels and occupation were comparable for the two cohorts. After the renovations, there was a significant reduction in classroom noise levels. These reductions in noise levels, in turn, appeared to have positive effects on children's cognitive performance. Those in the quieter conditions were rated as having better language skills (e.g., the child's ability to understand others when spoken to, the child's use of language, and the child's ability to be understood by others). Children in the quieter classrooms also performed significantly better than their peers in the noisy classrooms on items from the TERA (Test of Early Reading Ability) testing for children's recognition of letters, numbers, and words."