Soundproofing a portable building to use as drum studio

Hi I have undertaken a soundproof building project before, but due to moving house I plan to commence a new project early next year. I'm considering using a portable building as this will save me having to build - I can't afford to do a full on building project. The portable cabin I am considering is here: http://www.ebay.co.uk/itm/Portable-Cabi ... 1118520685 The main question I have is this. The width of this building is just right to fit in to the space I have in my garden. However, I need to maximise the space inside. I don't think a 9 inch air gap between 2 leaves will give me enough space. Any thoughts on how I can maximise space? Thanks James

In Norway there's a gouverment-founded music-cabin project: Pictures: https://www.google.no/search?q=musikkbi ... 59&bih=798 Official site: http://www.musikkutstyrsordningen.no/%C ... ge/brakke/ (Google translate / Google Chrome translate) I've tried the cabin-version of 23m3 (inside), and they're quite nice. 50db sound-proofing. I don't know how the walls are built. Your cabin looks smaller though.

Have you tried this? You can adapt the size of the booth to whatever suits you http://www.dawbox.com/V-Drum-Booth-8x8.htm