Thanks for the reply, I tried cleaning the fans but it didn't help, but I ended up putting together a much better fan, it's one of those $20 Hamilton Beach Trueair carbon filter fan deals. I ripped off the front screen faceplate and taped a plastic square bowl to it, cut a hole in the bowl and attached a PVC pipe with more tape, and it sucks the air through the pipe into the grow box, and is very very quiet. I actually have two good horticultural fans but they're just too noisy, and probably too powerful for my one plant space anyway.