I failed to mention there's already electricity connected with a lot of points around the garage. I'll be happy to just run things off the currently installed power points.
Right, but after you build the inner-leaf, all of those will be inaccessible, on the other side of the wall...
I'm definitely going ahead with this construction so it's just a matter of more learning about the most effective isolation design and working towards that financially.
I'd suggest two books: "Master Handbook of Acoustics" by F. Alton Everest (that's sort of the Bible for acoustics), and "Home Recording Studio: Build it Like the Pros", by Rod Gervais. The first one is great for learning about the principles of acoustics, and the second one is great for learning about how to actually design and build a studio, in terms of the construction materials, techniques and tools that you will need.
When you say beefing up the outer leaf/metal shell, would this be a case of attaching large amounts of acoustic insulation material?
Not really, no. Acoustic insulation, such as foam. mineral wool, and fiberglass, do not stop sound. They just absorb some of the energy as it passes through, but that's not the same thing. It's a bit hard to get your head around this concept at first, but absorbing sound is very different.
Think of it this way: if you need to mop up some water that spilled in places you didn't want it in your kitchen, then a sponge is a great way of doing that. It just soaks up the water, really well. But if you turn on the tap and hold the sponge across the end of the tap, the sponge does nothing at all to stop the water flowing through. The same with acoustic absorption: it's great for mopping up sound that is going some place you don't want it (treatment) but lousy at stopping sound from getting out of the building (isolation).
To stop water flowing out your tap, you need something solid and massive, and it needs to seal up tight against the tap. Ditto for sound: To stop sound, you need mass and hermetic seals. "Mass" means heavy, and "hermetic seal" means air-tight. No gaps. Not even the slightest tiny crack.
So "beefing up your wall" means adding a lot of mass to them, with some type of heavy construction material, such as drywall (= gypsum board, = plaster board, = sheetrock), or OSB, MDF, plywood, fiber-cement board, or similar panels that are heavy. And you need to attach them in such a way that the joints between them are seamlessly air-tight, all around the room.
I'm not sure if it is feasible to do that to your existing structure, for two reasons: 1) How would you attach that to the thin steel skin on your shed? 2) Can the structure safely support the huge additional weight that you'd be hanging from it? I suspect that the answer to #2 is "no", and to #1 is "can't be done easily".
That leaves you with the only other feasible option: build another isolation wall just inside that one. In this case, you would end up with a 3-leaf wall, instead of the much more desirable 2-leaf wall, but sometimes that is the only solution.
Regardless of the costs involved, am I naive in thinking this will provide an adequate level of sound insulation?
For the same reason I outlined above, that would not work. Absorption does not stop sound, any more than a sponge stops water.
I live in a reasonably remote area and don't have heaps of neighbours so don't need absolute silence outside, just a significant reduction in volume.
That is certainly possible, but you do need to put numbers to it. "significant reduction" is not something you can plug into the equations that help you figure out how to build your walls. You need a real-world number, such as 40 dB reduction, or 60 dB reduction, or 50 dB, or whatever it is you decide on. You can figure that out with a simple hand-held sound level meter.
- Stuart -
