Cohousing-L Mailing List: Re: How to soundproof ... floors/ceilings

[Tim Mensch (tim-coho-l]

"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  . . . .
>   
Michael Barrett wrote:
> 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
>   
Actually that PDF has a great example comparing staggered stud 
construction and double stud construction (the latter being the one 
Michael Black described above), and it said that double stud adds 
another 3-5dB of isolation on top of the staggered stud design, both of 
which being better than masonry, assuming I'm reading the numbers correctly:

8" cinder block:  STC of 43 (higher is better)
Double Stud/standard gypsum: STC of 51-58, depending on spacing and stud 
type
Double Stud/Double gypsum: STC of 66-80, depending on gypsum type

It doesn't say what happens if you start with cinder block and add 
layers of gypsum on top, though. Also, your perceptual difference may 
have been due to particular sound frequencies being blocked better by 
one kind of wall construction or another, since the STC number above is 
a curve-fitted average across all audible frequencies. Or it may have 
been that the neighbors had great tapestries that deadened the sounds 
from within their units... :)

Tim

--
Tim Mensch

Currently at Wild Sage (Boulder, CO): http://www.wildsagecohousing.org

Founding member of Tumblerock, a Boulder, CO area community in its forming 
stages: http://tumblerock.org