48 in. x 20 ft. Sound Barrier Quiet Wall

It shouldn't matter, especially if you add fiber batting as further noise reduction. But I found that the noise-suppressing fiberglass insulation is far more effective and much easier to install than this stuff.

The STC sound reduction rating on this material is 21. The Quiet Wall Commercial product has an STC sound reduction rating of 26.

You can put it there, but it won't do you any good for noise reduction. It's useless.

There are no VOC's in the Quiet Wall. Quiet Wall will not off-gas like PVC or rubber compounds that contain petroleum distillates. EVA is a naturally soft product and does not require VOC's to make it soft.

It's too damned heavy to install overhead. Also it would sag a lot, putting too much pressure on your drywall ceiling.

The material is an impermeable vapor barrier. If there is a vapor barrier on the warm (interior) side of the wall adding the Quietwall to the cold side of the wall will trap moisture between the 2 vapor barriers and cause a condensation problem. The only time it should be used on the cold (exterior) side of the wall is if there is no vapor barrier on the other side of the wall

Yes, but it won't be as effective, if you're going to put another layer of drywall anyways, why not just remove the existing drywall and add this. When it's sandwiched between sheets of drywall, it will not be as effective, right up against studs filled with acoustic insulation is what you need to get the best results. Some sound will still travel through, but it will be great at blocking conversation and normal household levels of noises, if it's going in a home theater the the louder the sound the more sound that will leave the room.

I used FLEX TAPE, it worked just fine to stick to the rubber. But the rubber noise barrier is useless.

It is designed to be used on the interior side of the exterior wall because it is an impermeable vapor barrier and can trap moisture in the wall cavity if it is placed on the exterior side of the wall.

There will still be noise traveling from the inside of the duct, it won't be that effective, just use fiberglass insulation around the ducts. If there is noise from the HVAC equipment, this will not solve that issue, the noise from HVAC equipment is most likely because your ducting is undersized, then the only solution is new ductwork. It sounds like you're describing sound coming from within the duct, and wrapping the outside will do very little if anything to stop the sound waves bouncing off the interior walls of rigid ductwork.