Thanks for the quick responses.
The other side of the wall from my listening room is the utility room with the furnace. However, there is a built in book case and a fireplace chimney between the two. From the utility room, I can see what the ducting and drywall wrap look like where it is above/in-front-of the bookcase. However, the part that is buzzing is above the fire place and on the other side of the chimney from the utility room so I can't get to it.
It looks like the aluminum framing is about 1" high and the ducting sits right above this. I think the ducting is vibrating against the framing, so pushing against the drywall causes the framing to push against the ducting and stops it from vibrating.
The aluminum framing is pretty flimsy so I am a little concerned that pumping too much of the foam through a small hole might cause the drywall to bulge. But I think this is still probably the easiest fix without pulling everything down (an expensive and messy fix).
The other side of the wall from my listening room is the utility room with the furnace. However, there is a built in book case and a fireplace chimney between the two. From the utility room, I can see what the ducting and drywall wrap look like where it is above/in-front-of the bookcase. However, the part that is buzzing is above the fire place and on the other side of the chimney from the utility room so I can't get to it.
It looks like the aluminum framing is about 1" high and the ducting sits right above this. I think the ducting is vibrating against the framing, so pushing against the drywall causes the framing to push against the ducting and stops it from vibrating.
The aluminum framing is pretty flimsy so I am a little concerned that pumping too much of the foam through a small hole might cause the drywall to bulge. But I think this is still probably the easiest fix without pulling everything down (an expensive and messy fix).