Uniformity of gap between walls

[khallgren]

Hello everybody.

I've got a quick question--what effect would differences in the gap between the two walls of a room w/in a room construction have on interior acoustics as well as the total sound isolation of the room?

For instance, if 3 walls and the ceiling have a gap of 6 inches, and the fourth wall has a gap of, say, 12 inches, what effect would this have on the interior sound of the room and its ability to keep music-type sound from getting to the outside world?

I've read in Everest's book that larger gaps help to absorb lower frequency waves (to an extent, and with diminishing returns), so would the entire room benefit from having one gap larger, or would a difference be noticed in just the one wall?

I would think that the sound passing into the smaller gaps would seek the path of least resistance and flank towards the larger gap, thus improving the isolation of the room--maybe I'll just try it and see.

I imagine any responses to this would be purely speculative, but I'd like to hear some other opinions if anybody's got them.

Thanks
Kraig

[knightfly]

Kraig, as far as sound PROOF-ing is concerned it's the "weakest link" theory that matters most.

However, from an acoustic viewpoint each wall's characteristics will affect the inside sound quality. Each wall is, effectively, a "panel trap" - and as such, the depth of the "trap" changes the frequency that the trap works at, so the wider air gap wall would work to trap more lower bass than the other three walls. This would, of course, also depend on what you used for paneling. Heavier panels would resonate at lower frequencies.

As a panel trap, this is good if you're looking to trap more low bass. However, as a WALL that is trying to STOP lows, it wouldn't be good. For that, you need two mass leaves (One on either side of the wall frame) at DIFFERENT resonances, so that the same frequencies don't find an easy path (resonance) thru BOTH leaves.

Back to sound PROOF qualities - all other things being equal, if the wider gapped wall is vented (gap to gap) to the narrower gapped walls, then that would tend to even out the isolative qualities of the dissimilar walls slightly - still, the "weakest link" comes into play, and the narrow gap walls present less absorption/blocking of sound. Overall, the TL of the entire room (omnidirectionally) would be about the same, with perhaps slightly less bass getting through.

Have I used up my $.02 yet? Steve