Almost free acoustic foam.

Guess what I came acrosssed? I was at one of my wholesalers and I spied a stack of charcoal colored foam sheets, about 2" thick in the main body, about 3 1/2" thick in the peak of the little egg carton looking pointy dealeys. (i forgot the technical description) This stuff looks just like the typical acoustic foam sheets that you can buy for $45 for like one or two, and they throw it away by the boxfulls. I told them Ill buy it for $1 a sheet for beer or pizza money and the agreed. Its packing material, they unpack and throw it away. Does any one have any input on whether or not a packing foam that resembles acoustic foam is structurly adequate to control noise, or is acoustic foam made different so that collecting and installing the packing foam will be a waste of my time? thanx d

looks just like this- http://www.uline.com/Browse_Listing_863.asp

Acoustic foam is open-cell polyurethane foam, if I recall correctly. If this packing foam is the same stuff, then it may be usable. Note the emphasis on "may"... Foam By Mail carries open-cell foam for a reasonable price: http://www.foambymail.com/soundproofing.html

....in searching out suppliers for a purchase of acoustic foam last year I learned that it has a density rating....usually "2 pound Ester"...if that's the case with this packing foam I'd say you've probably got a pretty good deal there...I came across a similar situation at an electronics store but they were unwilling to part with it as they used it for returns...

Packing foam is unlikely to be fire retardant in any way - if you value your safety, you would need to spray it with a fire retardant spray, which would put its cost probably equal to the foam by mail stuff, which IS claimed to be fire retardant - Also, foam doesn't work as well as rigid fiberglass or rockwool for most things - less lower mid absorption for same thickness. If you use this, besides finding a fireproof spray http://www.natfire.com/ you should mount it with the "pyramid" side toward the wall - it will work slightly better due to increased average depth of material... Steve

Good to know, good to know... That stuff made specifically for acoustics is just so dang expensive. And I have a lot of area to cover. Considering that fire that great white had, and if I remember correctly there was a foam insulation of some type on the ceiling that ignited. I am very safety minded.... I'd hade to cheap out and create a fire hazard. thanx for the input I may just bite the bullet and order up a few boxes of the gold....... CHIKCHING! D

Hmmm .... I wonder if the foam available at foambymail.com really works ... They call it sound proofing foam :shock: I have problems with dealers that mislead people into buying stuff :x

I know what you mean - that comment makes me cringe too. Short of "free", (which usually ISN'T) one of the lighter density rockwool products is probably your best bang for buck - works better than foam, is intrinsically fire proof, doesn't rot, only needs a cloth cover unless you WANT to build frames, can be hung by using "impaling clips" and construction adhesive, works better than foam, works better than foam, works better than foam... Did I mention that it works better than foam??!? :? Steve

Short of "free", (which usually ISN'T) one of the lighter density rockwool products is probably your best bang for buck

Total agreement. I would write more, but there is nothin more to say. Steve said it all. Andre

Every once in a while someone asks about something like rockwool and next pops up a link with the product. Beuller,... Beuller,... Beuller.. :) I'll buzz around the net a bit to see what rock wool is and looks like. My framing is up and I will wire it soon, so sheet rock paint and finishing arent to far away. If I plan on using rock wool, Id like a mental picture to think about. g

Foam, "Rockwool," whatever... :roll: :D Seriously, just thought I'd let folks know that you can order Mineral Fiber (same stuff as "Rockwool") in 2" or 4" thick 2'x4' sheets from any Auralex dealer. Ours is 8 lb/ft³ density. Absorption coefficients are on our Master Table (PDF download). Price is probably not "almost free," but we try and keep it competitive. :wink:

Sorry Jeff, that foam comment wasn't aimed at you :oops: 8 PCF - have you done any comparisons on ACTUAL room effects vs lighter weights to see what effect the higher weight/density has on grazing incidence at mid/high frequencies? Or are you using a specific cloth covering that helps that some? Curious minds (read T-W-I-S-T-E-D) want to know, an' all that - BTW, I can top your avatar for "ugly" without even resorting to a passport photo, but John would get pissed if I scared off ALL our members :cry:

Steve, > I can top your avatar for "ugly" < Hey, that's "Milton" (Stephen Root) from Office Space - one of my all-time favorite movies! --Ethan

Steve, No worries: Didn't take any offense. Reason why Auralex carries 8 lb/ft³ Mineral Fiber: Because it's the best for improving isolation. This increase versus standard "pink" batt insulation is marginal, but oftentimes situations requiring maximum isolation need all the help they can get! :D As for its absorptive properties, I have no more information than what you can readily find in our Master Table (above) and through other manufacturers' data sheets. I have tested fabric-wrapped 705 for grazing incidence absorption and it does go down. (By how much varies with frequency. E.g., at 2 kHz, it drops 40% or so.) I have not tested Mineral Fiber in the same configuration, with or without fabric. I have a hunch that, either way, it would measure about the same as the fabric-wrapped 705. Finally, no particular fabric in mind. We are a GoM distributor, so we tend to stick to their more common styles. Does that help?

Yeah, thanks - I'm a bit curious on the "improves isolation" comment though - is this for in-wall use, or as a gobo? And at what frequencies? Steve

Steve, In-wall use. USG did some studies eons ago about using higher density insulation to improve STL/STC. What they found was a marked difference between 0.7-1.0 lb/ft³ "batts" and 3-8 lb/ft³ "boards," like Mineral Fiber. The difference was only 1-2 STC points max (for "standard" wall construction) and the changes were mostly at 500-4000 Hz. Again, nothing to write home about, but for the more critical commercial and industrial situations, it could be the difference between being visited by OSHA and not. FWIW, they found that there were diminishing returns above 8 lb/ft³. They asserted that 2.5-4 lb/ft³ was "optimum," all things considered. But they had also just developed a 2.5-4 lb/ft³ insulation that they wanted to sell the poop out of. Having worked with myriad studio designers over the years, we've found that they have a preference for 6-8 lb/ft³. Some swear by it. YMMV...

Just spent a little "quality time" with IR-761, looking for correlations - the only wall constructions I found that had a counterpart with different density insulations were all one layer of 16mm gypsum both sides, using 90mm steel studs - these were 93-002 (used 75mm of 44kg mineral wool) and 93-003 and 338, which used 83mm of 98 kG mineral wool - all examples were essentially identical @ 50 hZ, running around 21-22 dB, but the lighter insulation came in 3-4 dB BETTER for STC, which seems to be exactly opposite of the USG insulation density report which (in a roundabout way) claimed that heavier insulation worsened LF TL, while lighter insulation IMPROVED the LF TL. Also found this - http://www.naima.org/pages/resources/li ... /BI405.PDF which basically says same STC regardless of density, that only thickness matters, and that the first inch is 'way more important than the rest - Starting to be even MORE convinced that for in-wall, anything but closed cell foam is fine, just throw it in there and obsess about something ELSE... Steve

Thanks for the research Steve.

Steve,

knightfly wrote:

which seems to be exactly opposite of the USG insulation density report which (in a roundabout way) claimed that heavier insulation worsened LF TL, while lighter insulation IMPROVED the LF TL.

Are we talking about the same report? Mine is a technical report from Form & Function (FF-85-2B).

Starting to be even MORE convinced that for in-wall, anything but closed cell foam is fine, just throw it in there and obsess about something ELSE... Steve

And I would generally agree: Empty is bad. Solid (closed cell or hardening foam) is bad. Low to medium density fuzz is good. But again, I go back to the fact that some consultants and designers swear by the heavier (but not too heavy) stuff. And as long as those guys are demanding it... :) One other thing I will say about higher density (6-8 lb/ft³) Mineral Fiber (or other fuzz): You can't beat it for seating risers. I realize this is OT, but it also applies to floated floors. We always suggest our Mineral Fiber to fill seating risers in home theaters. The reason we do this is risers or floors filled with lower density stuff "ring" more. We experienced the unfortunate drawback of lower density recently with a seating riser where we had no choice but to drill large holes in the riser and blow in cellulose insulation. While the difference between the cellulose (~1 lb/ft³) and empty was drastic, it just did not perform as well as the Mineral Fiber risers we've done. Still a little resonance in the 20-40 Hz range that might be annoying once the subs are fired up. But then again, kids these days; they LOVE the bass... :shock:

I was referring to this page - http://www.usg.com/Design_Solutions/2_3 ... onperf.asp I have to agree on the risers/floors thing - this was forcibly etched into my brain (and ass) last year; Ann and I went to an Earth Wind and Fire concert in Portland; held in a converted theater/auditorium - they thought it would be cool if the drums were set up on this "tower" - so there was a riser about 4' tall on stage, fairly large, where another riser (about 4' tall) sat on top - the larger riser also held some dancer chicks, the upper one held the drums. If I could have chopped off the drummer's feet, the concert would have been very enjoyable - as it was, it was only bearable because we both had earplugs, and even then it sounded like "baby just got a new 10 KW sub" - and hadn't yet discovered there was a setting other than "12" - As you also mentioned, the younger whelps in the audience (who probably thought they had "discovered" this "new" band, BTW) didn't seem to mind... Steve

Steve,

knightfly wrote:

I was referring to this page - http://www.usg.com/Design_Solutions/2_3 ... onperf.asp

Yep. That's the one. Thanks for the link. I also edited my post above to reflect their actual conclusion: 2.5-4 lb/ft³. (That'll teach me to skim...)

Jeff: Do you have the graphics that go with the article? Several parts of the text refer to them, and they are not on the USG page. Thanks Andre

Sheesh!. My comments are for all the newbies that want to pop in here on this site, look around for a bit, and figure they are now experts. No way! I havent a clue about anything your talking about. Stay sitting down, dont get up to explain. All the little abreviations, technical words, makes me realize there is a lot to this if one wanted dive into it. Dont bother to explain, If I spend enough time here, Ill pick some of it up. Its just a little humbling....... thats all. d

D, sorry about that - you just got your thread temporarily hijacked; Andre is better versed in a lot of this stuff than I am, Jeff is the chief acoustic engineer for Auralex, and I've been studying this stuff off and on for over 20 years; I can see why it would seem a bit overpowering when we all stop explaining things and just start rapping on some level where we're temporarily not trying to explain basic concepts - not to worry, ask ANY question you have, someone will take a crack at it. That's the idea here, mostly. Sorry about the diversion... Steve

Nah, its totally fine. My question about the foam was answered fine. As you guys with more knowledge and lingo chat, I just realize that this studio thing can be really indepth... d