We have a rehearsal room in a large garage that is 22 x 8 x 16 ft (WxHxD). The problem is that we need to build a room within the room that will be able to dampen the sounds of a heavy rock band (the loudest of our clientele produces about 110dB on a good day!). Our biggest concern is a group of houses outside the back wall of the studio. If we could stop the sound escaping from the back of the room, that should be enough to allow bands to practice every night without disturbing the neighbours.
We only have limited knowledge about where to begin on this project, and we do not want to spend lots of money on something that might not work. Could you suggest anything?
Editor In Chief Paul White replies: The usual weak points are doors and windows, so you'll need double doors with an air gap between them, double or triple glazing (block off unwanted windows if possible) and seals around the doors and windows to make sure the entire room is airtight.
If the walls are solid they probably don't present much of a problem, but you can put battens, Rockwool infill and layers of plasterboard on the inside to improve things further. You also need to treat all sides of the room, not just one side: low frequencies are not very directional, so they'll get to to your neighbours whichever wall they escape from.
I'd also recommend reducing your playing levels, as the daily safe exposure time at 110dB, before long-term hearing damage becomes likely, is around 12 minutes! Use power soaks or smaller amps to get the right sound at a lower level. Rumoured new legislation is apparently going to put a cap of 90dB on gig levels soon anyway, so you'll need to work out some way of making less noise all round.