cutting a room in halfish acoustically

Hi Billm,

I think the blankets would have to be pretty thick and heavy to appreciably attenuate the sound. I know that air gaps are valuable in velocity bass traps, as they put the absorptive stuff closer to 1/4 of the wavelength of low frequencies, as measured from the node which occurs at the wall. But a blanket isn't massive enough to cause a node, so I don't know how well air gaps between the blankets would work. I don't imagine they'd do much.

How much attenuation do you need between each side of the room? Or does that matter? I mean, do you intend to use the other side for recording while you're listening? Maybe there are loud noises coming from the other half that you're trying to shut out?

-d

Ah, okay. That makes sense.

It's a paradigm shift for me to think about a 45 foot room, cuz I'm trying to make one work here that's not even a fourth of that volume. And a fridge? Pinball? I'm moving in.

Hmmm... Maybe some portable dense absorptive panels, open on both sides -- aka, "gobos" -- that you can put in the center of the room when you (we? lol) want to listen. So any sort of "slap back" 80-90 msec delay that you'd otherwise get off the far wall would have to travel through the gobo twice. A single layer of 4" of rigid fiberglass or equivalent (like rockwool, shredded jeans, etc) would probably work better than multiple blanket "curtains".

In fairness, though, this is all coming from intuition, not experience. And, I've seen cargo blankets used in professional studios to lower high-frequency leakage between microphones. Most of the positional / timing information is contained in mid to high-mid frequencies, so maybe attenuating those is enough to keep the listening side clean.

That having been said, though... Nah. Bass frequencies travel a lot farther through air than mids or highs. An 80 foot round trip isn't going to do anything to stop them, and I really think they'd tear through blankets too. I imagine the bass there now sounds pretty loose and squishy.

Blankets would probably be easy to try, though. Hang some up, put on some tunes, and go listen by the pool table. Anything you hear there has escaped from the listening side. If the bass isn't *significantly* quieter, then you can assume it's also getting back in the same way it got out, and at close to the same level, with an 80 to 90 millisecond delay. And if it IS significantly quieter, I'd bet you're standing in a null. So don't just listen by the pool table. Listen on both sides of it, and by the fridge, too. With the untreated modes going on, picking one spot won't let you hear how much bass is escaping.

(Anyone else wanna chime in?)

-d

Yes, "isolate" is too extreme a word for what I envision billm is envisioning. The studio I interned at just used cargo blankets to attenuate the SPL, to mitigate mid/high comb filtering between the mics. Even a round-trip through a 4" gobo prolly won't give you a lot more 6dB loss, but at least a gobo would make a dent in the bass freqs. (6db is a total rough guess on my part here, as I haven't done it myself.) Again - that's far from isolation. That may be enough to make the bass sound better, though.

-d

Might be cheaper to build some baffles. You can hang R38 or something inside of a frame. Cheaper than a stage curtain, probably.