This piece by Arline L. Bronzaft on the effect of classroom noise on learning is really interesting and relevant with a lot of links included.
A recent report on the impacts of background noise on children’s speech and learning referenced a study linking activity in the auditory cortex to a child’s difficulty in identifying sounds in a noisy environment. Another recent study linked noise to lower math scores in classrooms.
Interestingly, it was over 40 years ago that a student in my environmental psychology class informed me that her son and other children attending school near an elevated train track in Upper Manhattan were having difficulty learning in the class. She asked if I could help with the noise problem because I had been lecturing on the effects of noise on behavior.