I had exactly this same problem in a condo I owned once. Instead of
having the fitting go directly into the room, I re-routed it inside
the closet through about 6' of flexible hose. I did get a little
pressure/flow drop, but not enough to present a problem. The noise
level reduction was amazing. Before I did that, it sounded like a 747
in heat. I had to cut a hole in the side of the plennum, block up the
old hole, etc. Parts at Lowes, and about an hour's work. Cost $50,
maybe.