In double wall construction...

Michael Jones · Post by **Michael Jones** » Sun Sep 21, 2003 7:55 am

...what's the optimum distance between walls?

Also, what's the acceptable minimum?

knightfly · Post by **knightfly** » Sun Sep 21, 2003 12:24 pm

"what's the optimum distance between walls?" - 50 feet.

"Also, what's the acceptable minimum?" - 1", if you use two 36" poured concrete walls...

OK, now that I've found my Librium... (sorry, Michael, couldn't resist - what can I say, I'm EVIL - MWOO-HAHAHAAAA...)

All seriousness aside, Here's a little "toy" I found the other day, it's a crippled demo but still VERY useful - the demo doesn't let you change wall material (1/2" gypsum only) but you can specify multi layers, distances between leaves, and it does GLASS too (not laminated in demo) I'm just getting a chance to "play" with it, but found that two glasses 15 and 19mm (5/8 and 3/4") placed 300mm (12") can keep up with some pretty serious wall constructions, even at 50 hZ. (Assuming they are NOT operable windows...)

http://www.insul.co.nz/download.html

Got a report that the FULL version costs about $1000 Eur, so probably won't be ordering that soon (gotta pay for the full ETF hard/software package)

If splaying glass, I'd use the narrowest air gap for calculation purposes, and just assume it gets better with distance (kinda like relations with a skunk -

) - actually, similar to said relations, the CLOSEST distance would be the telling condition...

Between the Insul calculator and this

http://www.domesticsoundproofing.co.uk/tloss.htm

you should be able to come up with some reasonably accurate predictions of wall performance.

On the Transmission Loss link, note the effects of damping at low and high freq - (insulation touching panels should be a GOOD thing... Steve

knightfly · Post by **knightfly** » Sun Sep 21, 2003 12:30 pm

Forgot - the narrower the air gap, the more difference a slight change will make (inverse square law)

Also, going from 2 layers to three isn't as effective as from one to two - mass law, double the mass = 5-6 dB, so to get the same improvement in dB from 1 to 2 layers, you'd need to go from 2 to 4. At this point, you'd probably be better off calling in the Redi-Mix truck... Steve

Michael Jones · Post by **Michael Jones** » Sun Sep 21, 2003 1:18 pm

Thanks for the DL Link.
Pretty slick little program!

knightfly · Post by **knightfly** » Sun Sep 21, 2003 2:29 pm

Glad you likee... One of the things I like about it is it actually recognizes that sounds go below 125 hZ.