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.
So, it is the drywall itself that is moving?

If so, can you tighten it up to the frame?
Hi jaytor, if you have never used it be very careful with it.  If you put too much in it will expand so much to push out your drywall, easily.  It can probably bend studs, its that strong.
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.

Yes that will work to stop the vibrating. But you better think about it real good first. Because while this will stop the ducting and drywall from making the noise hitting each other, it will work by bonding them together. What this means is any mechanical sound or vibration in the ducting will be transmitted to the drywall. If its minor you might not notice even up close. But you could just as easily wind up turning the wall into a speaker that lets you hear really good all the furnace air noises and believe me you do not want that! Only you know how loud your furnace is, how close, etc.

But the alternative really good and proper fix is remove the drywall, secure the duct real good, install insulation, and replace, refinish and repaint. That's a lot of see's. Vs one small hole you plug up with some plaster and are done.

If it was me I'd try the hole. That gap filler really expands a lot. Don't drill, use something like a 16 penny nail to poke a hole. That way it will push the duct and not cut through like the drill bit might. Maybe even blunt the nail first. Push the duct back as much as you can, to create some volume to get more bond area. Then just blast it in there. Should work. Fingers crossed!
That Warnes drum by the way, dobro I think its called, yeah pretty powerful and.... repetitive....
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). 
Jetter, the idea that this type of product can bend 2 x4 studs has not been my experience.  Are you speaking from experience, or just going by what you've read on the internet?
I am a little concerned that pumping too much of the foam through a small hole might cause the drywall to bulge.

Not a problem. The way that stuff works it comes out goopy and bubbly and expands. It doesn't push, just spreads out in all directions, path of least resistance kind of thing. You'd have to pump a whole can in there to have a problem. Maybe not even then.

The more likely problem is it goes in and by gravity or whatever just doesn't fill in the right spot. But you're really only out the cost of a can so what's to lose? Worth a shot.
Yes, I did exaggerate a bit, on purpose to make a point to someone who may not have used the product. I would hate to see a tiny problem replaced with a big one. I had very expensive Marvin Ultimate windows installed where the installers used the expanding foam as a bit of insulation on two of the windows and to this day the windows are a bear to open and close. Yes, I have used it myself.

I do disagree with Millercarbon's benign description of the product just above.
Maybe they just did a poor job of installing, I really doubt that the foam could bulge 2x4 studs.
"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.
I agree with you audiozenology.  Really no need to analyze my comments any further as wl all have made OP aware that this stuff expands like all get out and can wreck "stuff" (yes most likely drywall or sheetrock name depending on the part of the country you live) if not used carefully.

213runnin, it was used between the stud and the wood frame of the window.  Per Marvin professionals it is not an uncommon problem that the foam can bend the wood frame of the window which is much thinner than 2x4.
Expansion is only a problem when there's nowhere to expand into. Duh.

Which was covered in the original.

Reading comprehension. Reasoning skills. Marvelous. Highly recommended.
jaytor OP
Strong bass causing buzzing behind the wall

Find where it’s rattling by placing your hand on the drywall playing the music that sets it off.
This will be the spot where you have to fill the square inside made up of the "studs" and "noggins" see link

The distance between the "studs" are around 20" and the distance between the "noggins" around 18" or the other way round.

This is the square you have to fill with the expanding foam, make a hole in the drywall to put the nozzle in and squirt the foam up and down inside in for about 6-8secs only, should be enough, then fix or hang something over the hole.

Cheers George
I've used this foam insulation spray on different occasions, and I'm going to have to call BS.  It does not exert pressure when it expands as jetter suggests.  Look up the "Great Stuff Pro" ad copy and you'll see they specifically say it, "expands to fill gap without distorting frame" for windows and doors.

I'm afraid that his window installers either didn't know what they were talking about or were covering for poorly constructed windows.  Or they were poorly installed.