# quick double drywall question for sounddeadening.



## dvand (May 12, 2009)

I'm finishing a basement and want some sound proofing for a future HT space. I'm planning on drywalling the ceiling as well as doing R12 in the joist spaces to provide some soundproofing to the upper floor.

After reading on these forums I'm considering double drywall on the sealing. My question is if there's substantial difference if it's only done on the ceiling vs the exterior basement walls as well?


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## bpape (Sep 14, 2006)

The ceiling will help but walls will help too. You'll also need to consider any can lights, outlets, hvac, etc. - basically any penetrations in the wall. If the walls aren't framed, consider framing them 1/2" short and using some DC-04 clips to isolate them. Much less expensive that RSIC and hat channel and will help some if you decide not do do double drywall and green glue on the walls.

Bryan


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## Matteo (Jul 12, 2006)

Hi Dvand,
You might consider using Quietrock or something similar. It may be cheaper than double sheet rocking your walls and will be lighter as well. 
Matteo


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## kujomujo (Apr 24, 2010)

Another idea would be to use sound/fire insulation. I've put two layers of Roxul Safe n' Sound insulation in the joists of the ceiling. I even left a space between the two layers. This works well. My only issue was that I had an air return in the ceiling, so no matter how much sound proofing I did, the sound just entered the vent and headed out into the rest of the house.

KM


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## kujomujo (Apr 24, 2010)

Oh, and to combat that air vent problem, I just closed it up and covered it with drop ceiling.

KM


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## Home Theater Guy (Jul 18, 2009)

dvand said:


> I'm finishing a basement and want some sound proofing for a future HT space. I'm planning on drywalling the ceiling as well as doing R12 in the joist spaces to provide some soundproofing to the upper floor.
> 
> After reading on these forums I'm considering double drywall on the sealing. My question is if there's substantial difference if it's only done on the ceiling vs the exterior basement walls as well?


If you do double drywall on any of the theater interior walls or ceilng, you're going to increase the effect of room modes substantially. A single layer of 1/2" drywall acts a low-grade pressure absorber, and would be much better for your theater room acoustics.


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## bpape (Sep 14, 2006)

While it will provide less absorption at the normal frequencies, it also does still provide some absorption, but now at a lower frequency. 

Bryan


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## Home Theater Guy (Jul 18, 2009)

I hope you didn't infer that I meant to use drywall to treat higher frequencies...or that 1/2" drywall is a room treatment in and of itself. My only point was that using double drywall would take away any flex that the walls would have. The modes (which are of course in the lower frequencies) would be much more pronounced, and sound quality would suffer as a result.


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## bpape (Sep 14, 2006)

Absolutely agree. My only point was that while it does in fact take away from wall effectiveness in midbass to lower mids, double still provides some absorptive characteristics at lower frequencies while also providing improved S/N ratio available by reducing overall noise floor in the room.

Isolation from structure and allowing the structure to flex are many times at odds to each other. All a matter of where you want to put your money and what your overall goals are.

Bryan


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## bbieger (Sep 15, 2009)

Double drywall will definitely help a great deal. Drywall with GG, even bettter. That GG is pretty magic stuff. The issue between just the ceiling and doing both ceiling and walls is that of you don't treat the walls, sound will enter the wall and pass around your ceiling via the framing. This is referred to as flanking. I wouldn't worry about room modes as your goal is sound proofing, not holly grail accoustic response. You can always address room mode issues (to an extent) with in-room treatments.

Based on the reports I have read, save yourself from expensive drywall and fancy fiberglass insulation and just use GG. I suppose if you really didn't want to double the walls you could stuff the upper 2 feet of your wall cavity with rockwool? Bpape- would that work or would vibration just pass through the framing? My 2" thick rockwool treatments really knock down the higher frequncies.
_Posted via Mobile Device_


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## Ted White (May 4, 2009)

Standard insulation works very well, and is great in hollow areas. R19 in ceilings, R13 in walls and soffits.


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