I lined out a 6x4 garden shed out with 3 cm foam and put an old square type ac in it. Initialy it was to be just used as an office but now the kit lives in it. The foam in no way cuts it for sound proofing and i have to play the kit with mute pads. What is the best and cheapest way to sound proof? Is it true that egg cartons may work. Its just a garden shed so the roof is pitched and only just hi enough to swing some stix. I am also concerned that what ever i attempt noise will still find the way out via my wall mounted Air con. Any tips would be great.