.

[OrangeCrush]

*

[SecretCode]

OK, I'm intrigued.

How big is it? Single or double garage? What is the construction - brick? Pre-cast concrete?

How sound-proof does it need to be? Do you want it block out outside noise, to be quiet inside? Or make noise inside that can't be heard from your house and others? If so, what kind of noise? Workshop machinery? A garage band with amplifiers, drum-kit, etc? Or something more private ?

[Upphew]

If there's a framework inside, it's quite easy to do, you buy the foam insulation and cut it to size then press it tightly into the spaces.

And thus you have built http://en.wikipedia.org/wiki/Diaphragm_%28acoustics%29
Bad one, but still a vibrating sheet. Use rock wool for soundproofing. Or some other porous and heavy material. One should also make the space air tight. Bad for ventilation, good for soundproofing.

[OrangeCrush]

.

[Upphew]

As such, it ought to have a BIT of ventilation.

Notice _three_ mufflers in ventilation tube.

[MC Deli]

OP, you should head over to the John Sayers forum. It is a bit daunting at first but there a few key concepts and practical solutions that can help you - and stop you wasting time and money. Perhaps the biggest take away is that with sound proofing (attenuation), you are only as good as your weakest link e.g. windows, doors, ventilation.

It is also worth reading about why 2 leaf walls vs 3, the benefits of an air gap, how to decouple and avoid structurally borne noise etc.

And don't forget, as a drummer, you want somewhere that sounds good to you. Don't skimp on acoustic treatment inside, and think about what you can do with your own volume/kit to get a good balance between a great playing space and happy neighbours.

Good luck!