A few questions on small garage/studio build!

Hi there, great forum i've stumbled across here! I'm currently in the process of converting a garage into a home studio in a residential area and would like some advice on an approximate ideal figure for the level of sound insulation/proofing that i should be aiming for. The building is currently a single skin garage, and obviously i'll be adding plasterboard and rockwool insulation between the walls - however having spoken to a dryliner who will be fitting the plasterboard, he has asked us for a decibel rating for the level of insulation that i would require. Based on this he can construct it all (wall thickness etc) accordingly. How much is a decent/appropriate rating? 60db? 100db rating? All that the studio will be used for is tracking vocals (so not really much louder than a lot of shouting!) and also for mixing - no live guitar tracking or drumkits! However, we need to be able to use the studio at night without fear of disturbing the neighbours. There are two windows and a door in there, which are all going to be replaced with double glazing (the door will be one of those double glazed plastic/pvc). Also - the floor is also concrete - a floating floor would be too great a task to undertake (and we'd lose too much in height as the ceiling is quite low as it is) - is it ok to use a leveller and then thick carpet tiles with a lot of rubber insulation underneath? Any help would be greatly appreciated Many thanks! Eddie

Eddie, you don't give much detail as to your existing construction so I'm not sure what your outer layer is; but for what you want to do, the equivalent mass of two layers 15mm plasterboard outside, then a separate inner frame (not touching the outer frame) with two layers of 15mm plasterboard, such that the plasterboard double layers are about 200mm apart, and the inner cavity filled with standard fiberglass insulation, should do fine. You'll need to examine your ceiling/roof/windows/doors to make sure they are up to the same specs, or it's no good. The top post in this forum "Dont even THINK......" has several good points and can help you get up to speed on this sort of thing... Steve