Strong bass causing buzzing behind the wall

I've got a spot in my new listening room (in the basement) where there is a drywall wrap around some hvac ducting along one of the side walls at the ceiling. The drywall is installed over thin aluminum framing. When I play music with strong bass (e.g. Jennifer Warnes "Way Down Deep"), I can hear buzzing in the wall. I set up REW to generate a sine wave around 50Hz and I can easily cause the buzzing. 

The good news is that pushing on the drywall in a particular place will cause the buzzing to stop. So I'm trying to figure out the best way to fix this. I was thinking of drilling a small hole and spraying some expanding foam insulation. Something like this:

But I'm not confident that this will stop whatever is vibrating, and once this stuff is in, it might be harder to deal with the issue another way. 

Any ideas? Thanks.
Ag insider logo xs@2xjaytor

Showing 2 responses by audiozenology

It sounds like whatever is behind the drywall is "hitting" the drywall as the drywall vibrates or vice-versa or the metal frame attached to the drywall is vibrating against the HVAC ducting. Pushing on the drywall either damps the drywall and/or pushes the two up against each other .. or both. Fortunately HVAC ducting does not care if it is bent :-)

Either use a drilling tool with a depth-stop and/or make one with layers of tape on a drill bit so you can drill the depth of the drywall and not further.  Wrap on the drywall with your knuckles to try to get a feel where the vibration is. Drill a hole in the drywall there (assuming it is not an edge).  Then push something blunt through the hole, an allen-key for example and see if something is right there. If there is, you can probably push something blunt like an allen key through the hole and push whatever is there backwards and then wrap your knuckles to see if it has stopped. If the HVAC is loose and sagging, then you may need to push it up, support it, then blow in some foam from a different hole.  I am with jetter, don't go crazy if you don't know how much space is there.

"It can probably bend studs, its that strong."   .... is what was stated. I don't know if that is true or not. Unlikely, because the drywall will give first, and it will, if the foam has no where else to expand.