Re: How to soundproof ... floors/ceilings
From: Michael Barrett (mbarretttoast.net)
Date: Tue, 29 Jan 2008 07:01:10 -0800 (PST)
 "Michael Black" <mblack [at] mblackarchitect.com> 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 
http://www.practical-home-theater-guide.com/support-files/making-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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