Please critique my new build

Sorry, I got the maths wrong in that previous post. Also, the positioning of the outer walls has changed slightly again. The two possibilities are: a) 100mm block > 210mm air/rockwool > 2 x 12.5mm plasterboard b) 190mm block > 120mm air/rockwool > 2 x 12.5mm plasterboard Same total thickness (now = 335mm). Which is best? Thanks.

(a) STC 78/50 dB @ 50 hZ (b) STC 83/42 dB @ 50 hZ The thinner block with wider air gap is better at low end, which is harder to stop. Therefore (A) is your best choice, provided there are no windows to muck it up... Steve

Hehe - you just addressed the window issue in my other thread. There's another factor which is that the thinner blocks are considerably cheaper, and easier to carry. (This latter part might not sound important, but I live in a terrace house with no vehicle access to the garden. All building supplies need to be dropped off on the side of the road outside the house, and carried by hand through to the back garden for the building. We're currently working on shifting eight tonnes of ballast for the foundations this way, and not looking forward to the blocks!) So I guess I'll go for that. But just out of interest - I take it from your figures that the thicker blocks and smaller airgap would be better for mid frequencies, but worse for lows. This is the opposite of what I would have expected, as greater mass is required to control lows. Strange... Thanks again for your help.

Just shows how important the air gap can be in msm calculations :?