I think it depends on how you exhaust. If you live away from other houses, I'd recommend exhausting outside. The noise on mine is very manageable that way. If you need to use filters to keep the air inside, then build a folded baffle port in the attic for the return air after it is filtered. That will help cut down on noise. Works like a muffler on a car by canceling noise as it changes direction of the air flow. Just make it over sized so you don't lose air flow because the exhaust is choked down. I'd make it equal to a 10 or 12" pipe. Jim.