DIY “Room Within a Room”
You will be very lucky to get complete sound proofing for your studio or rehearsal room, but for basic home recording or practising you will get away with partial soundproofing, unless your family/neighbours are really nasty, or you need to cut out the noise from low flying aircraft. When I was at college my landlady complained about my constant saxophone practising so I used to get inside a wardrobe to practise. This worked to a certain extent but was not very pleasant.
Note that acoustic tiling, foam tiles or eggboxes will only cut down reverberation inside the room, they do practically nothing to stop sound from being transmitted to or from the room.
The most basic type of soundproofing is to add solid matter to existing walls and ceilings: you can do this by fixing layers of thick plasterboard, however this will only cut sound transmission slightly. Double glazing will also help but if you need to be a bit more serious then you need a “room within a room”, ideally a “floating” room made from stud walls and ceiling with at least two or three layers of thick plasterboard on each side. This is basically a box “floated” on rubber so as not to transmit sound from the walls down to the floor of the house and then to all the other rooms.
To float the room it should have it’s own wooden floor that is sitting on a layer of neoprene rubber or specifically designed soundproofing mat. A cheaper solution is to try a couple of layers of rubber carpet underlay, but bear in mind that this will be the hardest bit to replace if you get it wrong.
For windows use thick glass (at least 1/4″), ideally double glazed and set so that they are not exactly parallel in order to cut down resonance. A single pane of very thick glass is better than standard sealed double glazing.
For a door get a 30 minute (at least) firedoor and seal around it with rubber, including the bottom so it will need a sill.
Now for the important bit:
OK, so now you have created some very effective soundproofing, but you will suffocate in this studio unless you either open the door every few minutes or work out some kind of ventilation system with baffles (see below). Air conditioning is a very useful but still needs ventilation or frequent door opening. The quietest air conditioners are those that gradually ramp up and down with the thermostat rather than the on/off type, I have a Sharp AY-XO95E which is quieter than my Macpro.
Ideally you need two of vent holes with fans, one for air in and one for air out. You can get by with just a fan on the extraction hole. Normal kitchen fans are quite noisy as they are bigger and faster than necessary for normal airflow as they are designed for extracting smells very quickly but if you get a 12v fan (available from Maplins, Tandy or Radio Shack), you can control it’s speed with a cheap all purpose power adapter that switches between 3v – 12v.
Here is a basic diagram of how to make a vent baffle that will help cut down sound transmission. The whole thing can be made out of 1/2 inch MDF and is about 4 feet by 2 feet by 2 feet. All the internal surfaces should be lined with rockwool (RW3) and sprayed with varnish or paint to stop dust and bits of fibreglass. If you don’t have room for this type of baffle you need to make sure the vent holes are as small as possible and that the ducts are as long as possible or lead into something like a chimney. As long as you don’t light a fire.