We have a cold air return that goes from the first floor to the basement through a panned joist (just a piece of sheet metal nailed over two joists). There are loud birds on the first floor, and we are trying to stop the sound coming down from the air return into the basement. What would be the best approach?
I was thinking of loosely covering the two joists with MLV / acoustical barrier from below. Would that work? Or should I put some sort of foam insulation over the duct first, then put the MLV over that? Any other ideas?
I didn't find the right solution from the Internet.