First let me say I've already done this. Haven't had a chance to really test it but I'm real happy with the results are this point.

I've came across this and wanted to get others input on the validity of these numbers.

link (http://www.nuwool.com/pdf/wood%20stud%20assemblies.pdf)

We double studded our walls and tied our ceiling rafters to the walls and not the upstairs floor. I had someone drop a tool box on the floor upstairs and I heard a light thud but that was it, and it was silent in the HT. In our walls we have over 9" of cellulose and in the ceiling we have over 13" so we have a ton of mass in there.

I am confused about the 10 point difference between the double stud and staggered stud wall. The double with double layers of 1/2 on each side is 66. The staggered stud with double 5/8 on each side is only 56. Is sharing the top and bottom plate responsible for a 10 pt difference? And what about the difference in thickness?

Big sharing the same plate makes a huge difference just so you know. Double studded makes a big difference because the only way the sound is going to jump from the inside wall to the outside wall is through the insulation/air. The staggered stud because they share the same plate you are looking at a point the sound can tranfer through (the wood). Whether or not that makes a 10 point difference is another story.

Also the thickness has more impact on the lower frequencies that aren't in the STC test. So if you are building a wall and want a better low frequency response then you want more mass, i.e. thicker drywall.

I am confused about the 10 point difference between the double stud and staggered stud wall. The double with double layers of 1/2 on each side is 66. The staggered stud with double 5/8 on each side is only 56. Is sharing the top and bottom plate responsible for a 10 pt difference? And what about the difference in thickness?


It is the mechanical connection at the top and bottom. That connection sort of exists for real-world double stud walls which are mounted on a common slab or floor, but in a lab generally speaking double stud walls are truly decoupled and mounted on seperate areas.

Its mostly mid/high freqs where stagg stud walls take a penalty relative to double studs, and in general for a given cavity depth lower freq's are quite similar for the two assemblies.