Re: How to soundproof ... floors/ceilings
From: James Kacki (
Date: Tue, 29 Jan 2008 13:15:39 -0800 (PST)
From the Canadian Code: (the data will be the very much the same in the US)

2 separated wood stud walls with 1 layer of drywall each side of the total assembly =STC 45 (can go up to STC 57 if acoustic insul. is used in the walls)

I layer of 8" conc. block alone =STC 50

So both are close and much depends on the detailing of the wall (resilient channels, acoustic insul., # of layers of drywall, etc. All of this info. on STC ratings for various wall designs are available somewhere: municipal codes, internet, your architect, etc., so best to look it up before designing your wall.
Yours in silence,

On 29-Jan-08, at 9:00 AM, Michael Barrett wrote:

 "Michael Black" <mblack [at]> said:
At Yulupa Cohousing we used 2 separate 2x4 walls separated with 1" min. of
air space.   . . . . . .  This system is supposed to offer
better sound control than masonry  . . . .

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Interesting since this is contrary to my experience living with both kinds. While I have been unable to find any published numbers to support (or deny) my experience but there is some data at walls-quiet.pdf

In the table from the link - (which lost its formatting in the copy and paste) - the number before the word "Note" is the STC- Sound Transmission Coefficient . The higher the STC rating, the greater the sound attenuation of the acoustical barrier: that is, a higher number is better. The link notes that the numbers don't add if you add attenuating elements together, i.e. two walls 5/8" Drywall both sides (at STC = 34) don't make an STC of 68.
I have no connections with any of the products being discussed.

Michael Barrett

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Construction Method - 2x4 wood studs, R13, with:

5/8" Drywall both sides 34 Note 4

Double 1/2" Drywall on both sides 38 Note 4

1lb Vinyl under 5/8" drywall 43 Note 5

Resilient Channel 24" OC, ½" drywall 43 Note 4

Homasote® SoundBarrier® under 5/8" drywall under both sides 45 Note 1

Resilient Channel 24" OC, 5/8" drywall 48 Note 4

QuietRock 525 on 1 side, std. 5/8" opp. side 51 Note 5

QuietRock 530 over 5/8" gyp on both sides 56 Note 5

Construction Method - 8" Cinder Block Wall 43 Note 2

Construction Method - 3.5" steel studs, R13, with:

5/8" Drywall both sides 45 Note 4

Resilient Channel 24" OC, ½" drywall 49 Note 4

Homasote® SoundBarrier® under 5/8" drywall both sides 51 Note 1

QuietRock 525 both sides 53 Note 5
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