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MrAngles 06-01-2012 09:41 AM

Soundproofing a basement room
Ted was a great help in my other thread but we started getting away from the exterior insulation subject of the thread so I thought I'd start a new one to discuss interior soundproofing.

Here's my current plan for the basement, I'll be soundproofing the theater room on the top right:

For the ceiling I plan on doing two layers of 5/8" drywall with green glue between the joists, followed by sections of the fiberglass blanket insulation that came on the exterior walls of the basement, and two layers of 5/8" drywall with green glue decoupled from the joists using whisper clips.

Exterior Walls
The exterior walls I think I'm pretty much set on after the discussion in other thread, 2" XPS foam on the concrete held up by 2" furring strips, covered in a single layer of drywall and capped off at the top with two (maybe more?) layers of drywall with green glue and a double drywalled soffit to transition to the ceiling.

Theater Room/Mechanical Room Wall
I'm pretty concerned about the wall between the theater room and the mechanical room, as the furnace is loud and will be very close to the wall. I was planning on doing a staggered stud wall with double drywall and fiberglass insulation, but after reading Building a Room Within a Room at again I saw the double wall concept and that appeals to me. What would be the most effective use of up to 12" of space here? Two 2x4 walls with 2.5 inches of space between them and double drywall on the outside of each? Or should I move them closer together and add more layers of drywall? Does insulation go between the two walls? Would it help to put a layer of drywall inside the wall?

Rear Theater-Mechanical Room Entry Wall
I figured I would do a similar wall here as with the Theater Room/Mechanical Room wall to cut down on flanking from the mechanical room, although I worry about what a standard door will look like on a 12" thick wall.

Windows on Wash 06-01-2012 09:19 PM

gregzoll 06-01-2012 11:32 PM

You really need to be looking at the threads over at There is a real science involved, that at times I think that it is overboard, but it creates a real listening experience. In particular, look at this thread The book they are talking about, gives you more information than anyone on here can give you.

Ted White 06-02-2012 08:42 AM

I was consulted for the Soundproofing portion of the Home Theater Book. Have a look.

Regarding the walls, if given a choice between more cavity depth or more mass, you would choose the mass.

Furnace noise won't make it through a decpoupled wall with the damped mass of double drywall. You might consider a third sheet of drywall to contain the low frequency explosions from escaping, however.

MrAngles 06-02-2012 09:43 PM

Thanks! So if I'm adding a third layer of drywall, am I just screwing that into the other two layers, or should I get some extra long screws so I can attach them to the studs? Or should I make my first layer OSB instead of drywall to make it easier?

MrAngles 06-06-2012 09:01 PM

Ted what do you recommend for doors? It seems like a lot of people use solid wood doors and there are the edge seals and door sweeps, but I'm planning on having carpet in both the room and the hallway and I'm wondering if a pre-hung external door would be better, since it's sealed on all sides including having a bottom plate in the jamb that will seal.

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