I will be in Yosemite for a week next September and I plan to camp in one of the campgrounds in the valley.

How noisy should I expect them to be at that time of the year?

Last time I was there, in April, Curry village was very rowdy after dark and friends who stayed there didn't get much sleep. (I stayed at the Wawona.)

Yosemite Lodge at the falls might be a quiet option, but I am happy camping and it would save me quite a bit.