How do I HUSH UP that duct? (1 Viewer)

My mechanical room is adjacent to my Ht room and I was wondering if anybody has any ideas on how to reduce the resonating noise transfer coming from the one of my main supply ducts and my return duct. The ducts run just above a door into the HT room (see pic) I am currently in the process of building a room around the furnace and such to keep the noise down and finish up the basement. I can get some acoustical duct liner and clips but that would require removing the ductwork and reinstalling it. Are there any sound damping methods that I can do from the exterior of the ducts? Has anyone tried using a material like dynamat? I have lots left over from my car installation but I don’t want to waste over a $100 of the stuff if it will not work.

John Manville and Owens makes a 2-3" insulation that may help I can't think of the name of it but someone on the board may know. It's not the regular insulation that goes in the walls

I think using standard R-13 insulation, which you can get in sealed batts, would do the trick just fine for little cost. You just need to figure out a simple way to keep it in place, but if you notice, the standard insualtion specifies it is for temperature and sound.

Carpet.



put some furry carpet on the duct, furry side to the metal. put another piece of carpet over that, furry side out. then cover over it all with drywall. Two layers of drywall. You can get carpet leftovers and mill ends for cheap.