For a domestic space there is much one can do to alleviate noise leakage. I'm building a home studio in my converted roof at present and here are a few things I'm doing which may help. It's not an exhaustive list but hopefully will give food for thought:
For insulation, use at least 100mm of Rockwool RW3. This has a weight of 60Kg/m3 and is one of the more effective materials when it comes to sound absorption.
Note that this may require you to batten out (thicken) the ceiling joists and rafters, as building regulations (certainly in the UK, and probably most places worldwide) require a 50mm air-gap between the insulation and the roof itself for ventilation to avoid condensation buildup. In my case I did not have to do this on the walls, only the ceilings. The guidance I was given by the building regs people was:
- Dormer face & cheeks – 100mm dense mineral wool batts + multifoil & resilient bar over face, then plasterboard.
- Rafters (counter battened to give 50mm air gap to roofing felt) – 100mm dense mineral wool batts + multifoil & resilient bar over face, then plasterboard.
- Flat roof- 50mm air gap to roofing deck, 125mm dense mineral wool batts + multifoil & resilient bar over face, then plasterboard.
Unless the floor is solid concrete, install isolation tape between the floor joists and the subfloor above them. In my case the subfloor is 22mm flooring tongue-and-groove board, and I have it sitting on Green Glue Joist Tape.
Do not screw the flooring down through the tape into the joists as this will negate the benefit of the tape. Rather, glue the boards together using a strong wood glue, running a bead along the entire length of all joins and have the floor 'floating' as a single large mass on the isolated joists.
I found that using a glue that foams up a bit while it's drying worked very well as it expands into the joints, although you will need to shave off the foam once it's dry to make it flush with the joints. Leave a small gap around the periphery of the floor.
For the walls and ceiling, use two layers of acoustic plasterboard, with one being at least 15mm thick, separated with a thin layer of green glue noiseproofing compound between the sheets. Ideally each layer of plasterboard should be different thicknesses but for a domestic space that may not matter so much.
The plasterboard should not be screwed directly to the wall, but mounted on flexible supports in the form of resilient bars or genie clips (the latter of which can support standard steel furring channels). Genie clips are more expensive but give an additional 4-6dB of attenuation over resilient bars.
In both cases, the plasterboard screws must only engage with the steel bars and not go through to the wall or studwork. This means that the entire surface has a few mm of 'spring' in it allowing it to flex back and forth.
There should be a 3-to-5mm gap around all edges of each wall (and the ceiling) to prevent them impinging on each other and compromising that movement. This gap should be filled with an acoustic sealant. I'm using green glue sealant for this.
A solid door, the heavier the better, will also help and it should be installed such that it is as airtight as possible (I'll be using compressable rubber strips) when closed.
It also may be possible to get acoustic glass fitted in your windows. This consists of a laminated double-glazed pane which has a layer of polymer sandwiched in it. Depending on the window size and whether or not you need to see out of it as opposed to just having it for illumination, you could also look at adding a layer of Clearsorber to the frame.
In short you're looking at a lot of mass, combined with movement. In total, the plasterboard and insulation in my studio (roughly 60m2 when the area of the walls and ceilings are added up) weighs about 2.5 metric tonnes. It's a lot of work and it's going to cost more to do but it's well worth the effort.
I'm sure others can give more advice, but the above is a good set of practical basics. All links are for illustration only - I'm not recommending any particular source.
