SOUND-DEADENING BOARD

[jazzman]

Steve,

Last night (July 30th) you quoted the USG manual to state that gluing sheets together is the way to go because, as you said

A wood-stud partition with 1/2-in. USG Sound Deadening Board base layer and 5/8-in. SHEETROCK Gypsum Panel face layer laminated to each side will provide STC 49. The same construction with SHEETROCK nail-applied will test only STC 36

You also said to ignore previous posts. Does that mean you no longer believe this is true, which you wrote July 28th:

As for fastening, you shouldn't glue the new layers on because it will make them act as one panel. That can be ok in some ways, because it lowers the resonant frequency of the panel and makes it harder for lows to get through (as long as they aren't at the resonant frequency) - however, using screws to attach the separate panels lets each act at its own resonant frequency, which further blocks sound (it passes thru more easily at resonance) by making the wall have multiple resonant frequencies, so no ONE frequency finds an easy path through.

This is an important issue, so I'd like to focus on it for a moment.

Your quote from the USG manual, the way I read it, does not really say that gluing is always better than using screws. In this case it is, and it's clear to see why. The Sound Deadening Board is serving the same role in this specific type of construction as does resilient channel, breaking the path of conduction.

But if you are already using resilient channel to do so, or if you are using a double stud-frame wall with separate sole plates, and those separate sole plates are resting on a couple layers of vinyl barrier or thicker closed cell foam or some other viscoelastic material, then you have already broken the path of conduction.

So the question is, if you have already interrupted that direct path, what's the best way to mount additional gypsum panels?

And we should probably be asking for what purpose, for that can make a huge difference as well. If we're shooting for a general increase in transmission loss as defined by STC value, that's one thing. But if we are most concerned about blocking more low frequencies, then the STC values may lead us off in the wrong direction. Here's a good explanation of exactly what STC is:
http://www.sota.ca/stc_info.htm

Any more light that you can shed on this tricky issue would be most helpful. (Heck, you're already extremely helpful...)

Lee

[knightfly]

Lee, I'm still working this out in my head as well - first, I know exactly what STC is, and that's part of what's confusing when picking wall designs for studios instead of "living space" - although any more, what with home entertainment centers and subwoofers, I would hope that eventually ALL building criteria would move to MTC ratings. Sure would make things simpler for us, huh?

So far, my interpretation of the USG info is (subject to change, as I learn/think more)

Solid fasteners thru a second/third layer of paneling (any kind) into WOOD studs are a big no-no.

Solid fasteners thru a second/third layer of paneling into RC are (maybe) OK, since the decoupling takes place because of the RC. Just don't "short out" the RC with a mis-placed, too-long screw.

Solid fasteners thru a second/third layer of paneling into STEEL studs are (again, MAYBE) OK, since the steel studs are the decoupling factor here. Need to study ALL these factors a lot more.

There are three basic types of screws for wallboard construction - don't EVER use the wrong one. Type W for going into wood studs, Type S for going into Steel studs or RC, and Type G for laminating panels WITHOUT having to put screws thru multi-panels into WOOD studs. The easy way to remember these (probably the reason for the designation, duh) is W for wood, S for steel, and G for gypsum.

Adhesives for laminating seem to be just the normal joint compounds, but they appear to assume you're using the Type G screws to keep the panels from slipping, and to make intimate contact between panels (layers, that is)

The USG manual also state NOT to use less than 1/2" for a first layer if using the Type G screws, and NOT to get the panel wet with glue for any extended length of time prior to assembling, or they won't hold properly.

Part of the confusion in my mind was caused by "learned" comments regarding the "causing all panels to act as one is a BAD thing" - Considering that other statements regarding good low frequency isolation stated that "lowering the resonant freq by adding mass" should be done for MTC improvements - guess what, this is EXACTLY what happens when you laminate multi-layers together - lowered resonant frequency...

My goal here is to (at least) work out the ideal combinations of materials/construction to build a quality "music wall" - one that can handle ALL frequencies equally well, for the least amount of money. I know from other reading that it's important to BALANCE the TL, or what little sound DOES get thru will be MORE intrusive than it otherwise would, because it sounds "funny". This means to me that you can't get away with "brute force bass reduction" unless you apply other principles to get equal "brute force mid/high reduction" - in fact, brute force doesn't even seem to work AT ALL unless you go grossly over-budget with double 6 foot thick concrete walls separated by 32 foot air spaces filled with insulation/sand/lead, etc...

Everybody, please don't jump on me with a thousand questions about this next statement, because I'm still looking for answers myself - but, one of the ideas I'm researching is whether the frequency balance of isolation values would be negatively impacted by putting all the layers of mass (except ONE) in a "mass-spring-mass) wall, in JUST THE OUTER LEAF. If this didn't cause problems with mids getting through, the wall would still have dissimilar resonances in the two leaves, good LF rejection due to the mass of the outer leaf, with the ADDED BONUS of keeping the inside leaf thin enough to add significant BASS TRAPPING thru panel absorber physics. If you built the wall so that there was intimate contact between insulation and the INNER panel, the damping would broaden the Q and improve the TL. This concept, if it would work, should lessen the need for gross amounts of bass trapping. Just a thought, I'm sure it's going to take some time to figure out (especially from a self-taught late-bloomer like myself)

I'm probably forgetting a few dozen things along these lines, but am planning a more thorough attack on this ASAP.

Everyone feel free to chip in with ideas, but please don't ask me for drawings of the "ultimate wall" just yet (if ever) - I'll share more when I actually HAVE more... Steve

[jazzman]

Steve, this will definitely interest you. Here's a discussion amongs acousticians on this very subject:

http://www.google.com/groups?hl=en&lr=& ... %26hl%3Den

[knightfly]

Lee, thanks very much for that interesting link, some definite "heavies" in conflab there.

I must be getting closer to the "holy grail" of understanding, nothing glaring jumped out at me on a brief scan - copied the whole thing to Word and will dig deeper as I can.

Apparently I'm not the only one confused by the "glue/don't glue" smoke screen...

BTW, does anyone YET know WTF a "Camden" really is???!?

[nukmusic]

Don't even THINK of doing that - the 5/8" firecode sheetrock is only about $6 a sheet, more mass, and NOT flammable. Insurance doesn't make kids not miss their dad, assuming they survive the fire.

PLEASE READ MY ANNOUNCEMENT AT TOP OF THE FORUM... Steve

Ya.. that's what I told my friend. Fire would not be a good thing..........looking where I work professionally http://www.nofd.com

I also watched "Marvel Mysteries" on the HIstory Channel(Cox Cable TV) about "adhesives". Did u know that Duck Tape was designed for the military to be used a a waterproof tape for ammo boxes....."Quack - Quack" But the military personal learned that it worked for all types of things. Man. it's funny how things start off. First time seeing "Liquid Nails"(a glue the acts as a nail). They said that adhesives will replace nails and screws in the future. I'll try to watch that show again because I missed the first few minutes.

Just out of curiosity, I'm new to this forum:
I didn't get how you shut the garage door, if it is just a wood frame partition it could be your weak spot, you should increase its mass as much as possible... masonry would be the best!

Cheers,

Lorenzo

Well Lo, the garage door is closed just like it would be normally, and can't be opened because I took the tracks and door-openner down from the ceiling and filled all leaks. I will build(framing done) the 6" wood frame wall 6 inches away from the door: drywall+soundboard+2x6 wood(insulated) + soundboard + drywall. I'm looking at using RC 's(instead of sound board) if it saves money. Hey......... wonder what a STC the wall 6" wall will have if a 4" wall is 49???????? maybe just a few db.

[knightfly]

"adhesives will replace nails and screws in the future" - How 'bout right NOW? from what I've read (not much, really) if you've flown commercially in the last few years you were being held up by glue - at first, that seems really scary - but when you think about it, if a glue is the right kind for the materials, it's not all that different from welded metal - and that's perfectly fine with almost everybody...

" I took the tracks and door-openner down from the ceiling and filled all leaks. I will build(framing done) the 6" wood frame wall 6 inches away from the door: drywall+soundboard+2x6 wood(insulated) + soundboard + drywall. I'm looking at using RC 's(instead of sound board) if it saves money. Hey......... wonder what a STC the wall 6" wall will have if a 4" wall is 49???????? maybe just a few db" -

J, be sure and thoroughly read that thread Lee linked to - I can see at least 3 mistakes you're about to make that will cost you both money and performance.

1. You should never (in any reasonable cost wall) use more than ONE air space. Insulation is considered an air space in this case. Sooo, if you've SEALED your garage door, that is your first MASS in your mass-spring-mass wall. If it's not heavy enough, you should either add more mass, or ventilate it so it's not there acoustically.

2. The USG manual is very clear on this - you should NOT use through-fasteners into WOOD studs for any but the FIRST layer. Where the problem would come up in your proposed construction is that Soundboard (celotex/homosote) is NOT STRONG ENOUGH to allow Type G laminating screws to hold for fastening a layer of gypsum over sound board, and there should be ZERO hard fasteners going through both layers into WOOD studs.

3. The subject of Lee's link is Coincidence Dips - in plain english, this means that you should NEVER build a wall that has both leaves built the same way. Even if you put one leaf on RC, the Coincidence frequency will be nearly the same as the other, solidly mounted side. So, if you were to put gypsum over sound board (not a good idea, period) on ONE side of the frame, then the OTHER side of the frame should have a DIFFERENT construction - say, 3 different thicknesses of gypsum wallboard, or two different thicknesses of wallboard with a layer of sound board sandwiched between.

For what you're doing, my recommendation would be to "un-seal" that garage door (because it will be a real bitch to add mass to it, unless it's already one piece and smooth) and then build a mass-spring-mass wall (your 2x6 frame) -

From what I understand right now, you would get really good isolation by putting at least two different thicknesses of sheet rock on the outside (next to the garage door), solid onto the frame (I hope you haven't fastened the frame in place yet) with the second layer laminated (check out my stickys on the USG manual, the page #'s are there) - then, tip the wall up into a pre-laid double bead of acoustic sealant (use Sill Seal first if the floor is uneven) - once the wall is up, then comes insulation and the inner layer. If you can afford it, what I'd do for insulation is to use a layer of 3-1/2" fiberglas batt pushed into the cavity with the un-faced side away from you, toward the outer leaf, then 2" 703 or mineral wool semi-rigid, and finally another layer of standard 3-1/2" fiberglas batt (face out), all held in place by RC (read the USG manual, search on "resilient", it shows you exactly how to install RC) - The insulation will not want to fit the cavities very easily, because you're trying to put 9" of insulation into a 5.5" cavity - my reason for this is to provide damping for the two wall leaves, which is widely believed to broaden the "Coincidence Dip", thereby reducing sound transmission at or near those frequencies.

Then, put a layer of 5/8" wallboard on the RC, and follow that with a layer of Soundboard and a layer of 1/2" wallboard. These, because they are on RC, can all be screwed to the RC (mark where the studs are, and AVOID that area like the PLAGUE when attaching to the RC.) This leaf of the wall should be NOT glued, only screwed to the RC - this retains the individual coincidence frequencies (supposedly) of each differing layer, so there is no ONE frequency that is resonant to all components of the wall. The flexing of the RC keeps through-fasteners from causing flanking loss.

With the outer side of the wall LAMINATED, that will lower the coincidence frequency of that side to below ANY of the inner layers and should help a lot with low frequencies.

Be sure to follow USG's recommendation of spacing the wallboard off the floor on the side with the RC, then caulking thoroughly with acoustic sealant - If you're using multi-layer on the intersecting walls, alternate the layers so you have a "Z" joint at the intersection - caulk each successive joint before putting the next layer up. Use 1/8" removable spacers at the floor, then once the layers are all up pull the spacers and caulk.

BTW, you're right about 6" over 4" (really 5.5 vs 3.5", til you add RC on one side) it will (with proper insulation) probably add only about 2 dB, but that's as much as you'd get from a third layer of wallboard, so why not?

Do yourself a big favor, and don't finish that wall without asking about any changes you plan - what tends to seem "right" for sound proofing, usually ISN'T... Steve

[jazzman]

Apparently a Camden is just a stud wall, named after the first place it was built over there.

Let's see if I've got this right:
Whether you glue or whether you screw depends on what you want to do.

To block more bass, glue. To block more evenly across the entire frequency spectrum, screw. Why? Mass law and coincidence dip.

You can predict that a certain mass will block a certain amount of sound at various frequencies. Theoretically the mass law works on a straight line, blocking less in the bass range, more in the mids, and still more in the highs, EXCEPT at the panel's own resonant frequency, at which more sound is let through. The thinner the panel, the higher the resonant frequency. (The resonant frequency of 5/8" sheetrock is about 2500 Hz, and of 1/2" is something like 3200.) So you combine several panels of different density/resonant frequencies so that together somebody in the bunch is covering the acoustic holes.

If you're stuck with using all panels of the same thickness, and you screw them together, you've got the same hole at the same range in the frequency spectrum. In that case you could glue the panels together, making them act as one larger panel. There will still be an acoustic hole at some frequency, but it will now be lower because larger masses resonate at a lower frequency. You have to decide whether that's good or not.

Other complicating factors: stiffening the wall with added bracing will damp the wall's vibration but will also raise the resonant frequency - it's a trade-off.

Again, when you glue several panels together, the glue tends to make the whole thing work as one, but the total performance becomes harder to predict, as it depends on the nature of each panel and the nature of the glue itself.

I've also read that you HAVE to use at least a couple of screws per panel even with glue for stability and security, or else the damn thing is just going to fall off over time.

Just looking at STC ratings of various walls obviously doesn't tell you enough to help you decide. That's why good studio builders like John Sayers and Rod Gervais with tried and true experience that goes way beyond the theory are so essential in leading us out of the darkness.

Lee

[jazzman]

put 9" of insulation into a 5.5" cavity - my reason for this is to provide damping for the two wall leaves,

Steve, you've been giving great advice - with the possible exception of this point. Angelo Campanella has a mantra of "fill but don't overstuff". I'd feel comfy with 6.5" of batt insulation in 5.5" space, though. I'm guessing that the reason for their admonition is that if you squeeze the batts too tight, they no longer absorb as well, i.e. they don't turn the wave energy into heat energy. Too stuffed and the energy may just transmit more than you want from one side to the other. It's a good intention to want the insulation to serve the purpose of damping as well, but it's just a question of degree to get it right.

One thing I've learned from all this reading is that the air space itself is very very important. The more air you can get between your two leaves, the better. One of the reasons why the RSIC-1 clips give you 7 STC points more than standard 2x4 walls with resilient channel has little to do with the materials of the clip itself, but rather that they add over an inch to the air gap, and make room for R-19 instead of R-13.

Lee

[knightfly]

Lee, the things we both believe to be true are apparently the same right down the line - as for the squished insulation, if you subtract the 2" of basically "non-squishable" 703 from the stated wall, you have 4" of space left - cut that in half, and you have 2" into which to stuff 3-1/2" of fiberglas, which to me isn't a very tight fit. OC makes their 700 series panels in a version that's purposely too wide for a stud cavity, just so they will bow enough to stay firmly in contact with the wall panels - If they can do that with rigid, it wouldn't seem (to me, anyway) that 3-1/2" into 2" would be too tight.

I agree completely that the air space is more important than generally thought - and maybe when I actually started trying to cram that much insulation into a wall I'd reconsider. Right now, it just doesn't seem like it would be tight enough to be detrimental... Steve

[jazzman]

one of the ideas I'm researching is whether the frequency balance of isolation values would be negatively impacted by putting all the layers of mass (except ONE) in a "mass-spring-mass) wall, in JUST THE OUTER LEAF. If this didn't cause problems with mids getting through, the wall would still have dissimilar resonances in the two leaves, good LF rejection due to the mass of the outer leaf, with the ADDED BONUS of keeping the inside leaf thin enough to add significant BASS TRAPPING thru panel absorber physics.

Interesting idea, Steve. Let's consider:

A standard gypsum wall built 16 OC absorbs .29 of 125 Hz, i.e. there's 29% less bass in the room at that point. Where does it go? Either it's turned completely into heat by the flexing of the gypsum panel, or some of it passes right into the wall cavity. (Common experience indicates the latter.) What happens to it then, and is that what you want?

Lee

[nukmusic]

for a better idea of what I am doing.
1. Temp. location for studio(12-18 mths).
2. $1000 budget
3. Garage door stays in (closed position). looks like regular home from the outside.
main 3 goals that I will not change. with the help from you guys I'm right on schedule. Thanks. I plan to build this studio design(thanks John S.) but on a large scale( larger rooms) at a commerical location in the near future using the double wall construction and metal studs:

http://www.saecollege.de/reference_mate ... s%202..gif

1. You should never (in any reasonable cost wall) use more than ONE air space. Insulation is considered an air space in this case. Sooo, if you've SEALED your garage door, that is your first MASS in your mass-spring-mass wall. If it's not heavy enough, you should either add more mass, or ventilate it so it's not there acoustically.

Gotcha on the one air gap and the weak sound board. I also thought about this before and I was right and just didn't know it

Of coarse you know that the areas left, top, and right of the garage door(thin non-isulated metal door) is constructed like the rest of the house. The floor is 8" slab and the The front wall is framed and still on the floor ready to be raised into place The garage door is not really sealed real good. IT has a nice rubber seal at the bottom that I will also seal with acoustic caulk and a rubber flap(water stopper) around the rest of the door on the outside. I cramed the small gaps around the door with insulation. The ceiling guide tracks have been taken down but the wall tracks are still up holding the garage door in the closed postion. I can push the new front wall up against the tracks?????

I did plan you use 5/8 drywall on one side and 1/2 drywall on the other with the sound board or RC's for all my walls, but..one question about the "Dip" thing. Is it better to allow a little on each freq. through(2 sizes of drywall) OR allow a lot of one freq. through(1 size drywall)? If I can get a STC of 50 with all the outer walls I would be happy(temp studio location).

One of the reasons why the RSIC-1 clips give you 7 STC points more than standard 2x4 walls with resilient channel has little to do with the materials of the clip itself, but rather that they add over an inch to the air gap, and make room for R-19 instead of R-13.

WHy not use neoprene pads or 1" thick rubber strips with the RC? Has any one every tested a wall with neoprene pads/rubber strips and drywall screwed into wood studs(no RC)? Just an idea Seems to me like rubber would absorb more vibrations then metal.

Thanks

[jazzman]

Docta'J, I can see now that what I wrote about the RSIC-1 clips is very misleading. I should have said, one reason the clips have a higher STC value is the increased air gap they create. Another reason is the fact that the rubbery part of the clip that touches the stud has 12 tiny feet, so there is less contact at that point. Yet another reason is that when you use the RSIC-1s with the hat track, you only have to attach to every third stud. Less contact points means less conduction.

So, J, to answer your question, neoprene pads aren't cheap either, you would need 3 times as many as you would need RSIC-1s, so the costs aren't that different, and the RSIC-1s are already proven to work better.

Screwing drywall through neoprene into studs still has a direct connection between the drwall and the stud, so that won't work.

In the RSIC-1, you've got a metal screw going through a ferrule (a little metal cylinder) that holds the rubber against the stud, and the rubber holds the hat track. So the drywall only touches the hat track being held by the rubber, it doesn't touch the studs.

Lee

[knightfly]

Guys, here is by far the best explanation of wall performance I've seen to date -

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

they are only very gently trying to sell their products, like their "soundmat" which is actually several times cheaper than similar products at places like Acoustical Solutions, Auralex, etc...

J, please pay attention BEFORE you tip up that wall - IF you're putting wallboard on BOTH sides of your 2x6 frame (and you should) then DO NOT, repeat DO NOT, seal that garage door. Just leave it as is, fasten it so it can't be opened, but DON'T CAULK IT !!!! You might want to fasten some black 6 mil plastic over the window panes so they reflect from the outside, making it harder for anyone to tell what's inside.

No, I wouldn't push the new wall right up against the garage door - both sides of the new wall need to be free to vibrate at their own separate resonant frequencies, or it screws up sound isolation. I'd leave at least a 1" gap there.

As to spreading out the coincidence dips, DO IT. Check out the above link and you'll see exactly why... Steve

[giles117]

Hmm their soundmat is a thermoplastic.

I wonder..

I will check a local supplier tommorrow to see if they carry such a product..

They are a major automotive supplier.

I am working on my live room and got all the neoprene I needed for (drum roll) $25.00 and still had some left over.....



Will check out this plastic thing.

Here is a Question, I notice with their design of a room in a room, the AFB is on placed physically on the outer wall instead of between the studs of the new wall. Any Ideas?? I am curious as I start the wall construction probably tommorrow.

And what thickness is that material I wonder???

I was considering either 2" or 4" Wool. Obviously 2" is cheaper ($2.00 per 2x4 slab for me)

Any Ideas???

Bryan Giles

[knightfly]

"I notice with their design of a room in a room, the AFB is on placed physically on the outer wall instead of between the studs of the new wall. Any Ideas?? " -

You lost me - what page, and which diagram, are you referring to? I saw nothing about a RIAR (room-in-a-room) on the page I linked to, and nothing wierd on insulation.

I think their stuff is about the same as Auralex SheetBlok, just a limp-mass layer... Steve