Soundproofing wood shed... worth the effort and cost?

Discussion in 'Acoustics (Live Room, ISO Booths)' started by Chris del Camino, Jul 20, 2020.

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  1. kmetal

    kmetal Kyle P. Gushue Well-Known Member

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    Perhaps snake is a better description? The only accurate things the guy said could be read from the gg website. ie its a constrained layer dampening compound. The other accurate thing he said was gg is best in certain cases. This is common knowledge. Its LF performance isn't better than the equivalent drywall.

    Nobody uses drywall, or any other isolation material for is frequency response, its used for it TL value (at various frequencies). That's why 100% of pro studios use acoustical treatment. Because isolation value, and room frequency response are different animals. This guy conflates the two. Same thing he did with TL and absorption coefficients. They are measuring two different things and are not interchangeable.

    But an unknowing person could easily "see the numbers" and think this guy knows something, and grossly over pay for an inferior studio.

    Big time studio designers use drywall because its cheap and pretty decent in the Low Frequencies relative to other sheathings. Its cheap mass simple as that. They use masonry because its cheaper than drywall to get high TL values, or other logistical reasons. You don't get isolation and accurate/pleasing acoustics from the same materials. It doesn't work like that. Nobody walks into a concrete room thinking "this is a good place to mix". A good verb chamber quite possibly.

    For music low frequency isolation is usually the biggest concern. Low Frequency absorbsion is often the biggest acoustical concern. The reason drywall and fluffy fiberglass are so common is because they perform best in those areas cost vs performance.

    This guy claims to know things the best in the biz don't... And then says outright wrong things like use construction adhesive.

    When it comes to isolation most of it is science, its figured out pretty darn well. The methods, the materials, the cost vs performance, its all well established. GG is interesting because it is fairly new, brian rivannas (butchered spelling) invented it 20 or so years ago.

    Until new materials are invented isolation and its techniques are about as good as they can be. Drywall, Lead, Concrete, and Plywood/OSB is what is tried tested and true.

    Id bet 100$ the "other constrained layer dampening" he uses is MLV. A grossly overpriced form of mass. Which does have a few good use cases. Id also bet this guy has another video talking about why different density sheathings are superior. Which has no test data to back it. Lol maybe ill search for the videos.

    When in comes to internal room acoustics, different schools of thought and methods have been defined and used. None of them perfect. We don't have the same grasp on acoustics as we do isolation.

    In places where weight is an issue and no more mass can be added, GG is a great way to gain isolation, without adding a considerable weight to the structure. For example went using resilient channel or whisper clips. If you can only supprt 2x layers of dw, gg can add some more isolation without going over the load bearing limit.

    This guy has a reputation for being misleading and outright wrong around other forums. He's been debunked many times.

    He simply feeds on the unknowing, misleading, using unsubstantiated claims (we use 'something' better), and conflating specs, to appear knowledgable.

    He may even know he's doing it.

    Either way he is not a reliable source of info.
     
  2. kmetal

    kmetal Kyle P. Gushue Well-Known Member

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    At some point its worthwhile starting a GG thread with tons of links ect. But my current set of related links isn't completely organized.

    This thread is great. Despite being 5 pages, its first several posts explain quite a bit. It even includes an itemized cost breakdown from Rod Gervias on a real project he used it on. Great explanations from Eric Desart, designer of Galaxy studio, one of the world's most highly isolated studios.

    https://www.soundonsound.com/forum/viewtopic.php?f=24&t=650
     
  3. Chris del Camino

    Chris del Camino Active Member

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    Kyle thanks for help explaining some of those calcs.. Roughly it sounds like the floor needs ~2100 lbs of mass to be on par with double walls. I checked the STC ratings of resilient vs double drywall and for the 3-4 points I gain but at an extra cost for the channels + hats, it doesn't seem worth it. Was going based on RSIC-1 and not whisper clips though. So 2100 (2" thick at 120 sq ft) lbs of self leveling concrete is over $1000 but the same mass can be had from 30 sheets of drywall ($300), except it'll be eating up 5" (8 layers of gypsum).. but the ceiling is "vaulted" you could say, since it's a gable roofed shed reaching 10ft at the top... whew.
     
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  4. paulears

    paulears Well-Known Member

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    It does appear that everyone has a view on green glue, but there seems NO independent evidence on performance. I guess because the damn stuff is too expensive to experiment with. With all the wall systems what gets me is how the weight of the walls is simply massive. If you use aluminium strip and isolation mounts it's quite surprising how much movement there is. The strip itself is designed to flex to assist with transmission. The rubber mounts are designed to flex too. The strip and the rubber visibly move when weight is added. I know that as there are lots of them, the weight of the sheet is divided by the number of mounting points, but with two, maybe three layers of plasterboard the gap you left at the bottom visibly reduced with each added sheet, plus I see no way to stop leakage underneath. A bead or two of silicon lets sound through far better than going through the paster layers. If you put three layers sitting on the floor directly into the timber that's a very good seal, and surely the timber being fixed to the boarding directly adds to the mass, and adds rigidity - which presumably allows these flanking paths access to the cavity. So maybe a layer direct to the timber, and then the isolation strip and mounts to the next layer of sheeting would be better. This is the snag. We have to use science and predict what will happen.

    HF clearly is constrained by travelling through thinner sheeting, so we're left with the bottom end. I suspect we're thinking that the kick drum pressure wave hits the first sheet and physically moves it, dropping the energy. Some makes it through the sheet, then finds a tiny gap with the beads of squidgy glue. The sound crosses the gap, losing a little more in the air space and the glue itself, then tries to generate movement in the deeper sheet, which is attached perhaps with the insulated mounts. Tiny savings in transmission through the inner to outer skins. However - we have fixings to consider. It doesn't take much to go through the aluminium strip and hit a stud, removing all the isolation from the components and how many of these mistakes eats up the benefits (if you believe them) of the Green Glue. Some people I read thought green glue was glue and thought it stuck the plasterboard layers together, so no screws were needed. Most people realise that the screws are needed, but each one compromises the isolation. The studio experts seem to use LOTS of layers for the mass, and these give the absolute values of reduction you can trust. The few dB from isolation gizmos is at best limited and at worst wrecked by accidental construction defects.

    I really w iso somebody like Green Glue manufactures would build a simple structure with and without the product and actually prove the product's worth. It seems a very simple thing to do, but they don't? This worries me. Why not? Do it and be able to prove the performance.
     
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  5. kmetal

    kmetal Kyle P. Gushue Well-Known Member

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    Paul, Eric Desart accurately describes excactly how green glue works, the physics of it. It dissipates vibration into heat. That is where the engery loss occurs. The front panel and rear panel exhibit similar levels of vibration, the gg dampens the entire sandwich.

    Im not seeing any solid ground for your duspute of the gg test data. Are you saying the 3rd party/independent, certified lab is making false claims about GG? Or GG is publishing false data. Read their brochure, they literally have copies of the ACTUAL test report. Your suspicions seem un-warranted.

    If you look at the graph, you will notice they tested an assembly with gg, and one without between the dw layers. They did what you requested already.

    It would be interesting to see the performance of a true double walls assembly with and without gg. They used a single wall. This is a favorable situation for gg. This again is up to the user to determine when gg is applicable.

    Marketing language is excactly why test data is king. Marketing is well you know.... Not a test lab dara set lol.

    Its also important to seperate lab data, computer models/math, from the real world. The results from feild tests and lab tests are never identical, neither are results from different labs. But with isolation assemblies they are usually in the ballpark assuming proper construction.

    You can't say a product doesn't work on the grounds of it being installed wrong. My sm57 wouldn't work well with a guitar cable.

    In fact if you look at the data sheets, there are test examples where channel manufactures short circuit the channel by hitting studs. The show the % reduction in isolation at different error rates. A couple screws hitting the studs reduces like 10%, but that grows very quickly with a few more erroneous screws.

    One advantage to risc1/whisper clips is they are near impossible to short circuit in this manner, however clip layout is still critical.

    Resillient channel is good for 4-6 db, but trades hf isolation for LF isolation. So no best suited for full range audio. Risc1 clips are good for 9-10db and across a broader spectrum. These are facts. Tested facts. Riverbank labs couldn't care less about risc1, they wouldn't harm their world class reputation to falsify testing.

    The reason we use lab data not just feild data is because feild data has many more variables, and is subject to the individual testing method.

    As far as caulking goes, rod and the USG handbook both show details for caulking at the floor junction including the use of backer rod. This juction is also covered by moulding most often. Flanking between the wall and floor isn't necessarily an issue. You don't have to isolate the inner leaf from itself. The walls floor and ceiling of the inner shell all touch each other, flanking is not a concern here. Only when flanking bridges inner and outer leaves.

    Its important that reputable isolation products be used where they are best suited. There is no one stop solution. But we cannot conflate poor integration or erroneous installation, with notions that a product doesn't work as tested. Its simply not true.

    If you try and gain 10db based just on mass law you get an exponentially more expensive assembly than one using decoupling. That's why decoupling is so critical in isolation. Because the mass law has exponential costs/diminishing returns. But mass is the only way once decoupling is met (aside from gg).

    Take a wall with 2x layers each side. Double that for 6db, now at 4x layers each side. Double that for 6db, now at 8 layers each side.

    What's cheaper, 16 layers of drywall hung, and taped, or some whisper clips and hat channel.
     
  6. cyrano

    cyrano Active Member

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    Eric never really approved of Green Glue. He always said is was expensive snake oil that could work in a very limited number of cases. He was one of the two people I was referring to. Unfortunately, Eric is no longer with us.

    The problem is that by adding a layer, you come into a triple-leaf construction that could very well be a lot worse than just using a double layer.

    You said it yourself. Data is king. The data needed to calculate a triple leaf is only very seldom available for DIY materials. And you need ALL the data.

    Hec, the spreadsheet Eric made to try to explain the problem is still floating around the net.

    How things go in the US when talking about acoustics is simple: the loudest mouth wins. In casu, the one with the biggest pockets. Like when Ethan Winer sued the studiotips forum. You can read about how Eric felt here:

    http://www.homerecording.be/forum/t6106.htm

    Fortunately, I'm not ready to start that war allover again. I would just ask you to not use Eric's words in vain, as GearSlutz has already done a sickening amount of that kind of commercial religious idiocy.

    The other person I was referring to, Bert, sums it up quite nicely:

    Yes. It's in Dutch. Use Google translate. Translation to English seems to work most of the time.
     
  7. paulears

    paulears Well-Known Member

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    I get the theory, but that video did make sense in some areas - they do claim a lot, but I don't accept data that seems to have solidness in some areas but vagueness in others. All I can base my opinion on is my own experience, and frankly, much of it looks like marketing, and I cannot say the one with green glue, virtually the same design and space as the one without, performs better. Essentially - an awful lot of money went into the latest one, and I hear none of the claims on their website. I know the physics, but the reality is less exciting.
     
  8. cyrano

    cyrano Active Member

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    It is simple, really.

    To isolate, you need mass. What you put between the mass, doesn't influence anything except for maybe a tenth of a dB if it's solid.

    In case you put air in between, you need to fill it with a dampening material.

    Putting a flexible layer in between is just complicating things.

    But sheer mass is the only thing stopping sound from traveling through any material. There is NO magical ingredient.

    If you want to calculate, you need ALL data. These numbers are never ALL available/accurate. So the only way out is measuring and experimenting with the materials you can cheaply and easily get.

    Architects who can do acoustical planning are scarce. I don't think they could help in this instance.
     
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  9. kmetal

    kmetal Kyle P. Gushue Well-Known Member

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    You did not provide any data to support your claims yet. Test data. There is no data showing GG doesn't work, if there is i haven't seen it, neither has any other masters in acoustics.

    Interesting since several of his posts say the exact opposite of your interpretation of his stance. In addition to lab data, here is several quotes from respected acoustics experts, supporting that the GG works. None of them sell GG or Acoustic Products. I'll post the text here (or the main point) since dead links are frustrating to future veiwers.


    -------

    https://www.soundonsound.com/forum/viewtopic.php?f=24&t=650

    Eric Desart (pg 1, halfway down)

    "But GG IS good. When one chooses to build light-weight walls, gypsumboard double leaf walls are about the most efficient option.
    Double leaf walls are limited by some phenomena, mainly the mass-spring resonance (and in that so-called normal wall the structural resonance) and higher up the coincidence but which mostly isn't that defining in the overal insulation.

    What GG does is OPTIMIZING such walls, which indeed can show significant improvement.

    Further in Studio terms it certainly can have advantages because one suppresses the drumskin effect undamped panels can show much more enhanced.
    In fact GG makes the panel sandwich as dead as possible, and I do believe better than anything I saw before.
    GG doesn't leave much space (if any) for improvement."

    -----


    https://www.gearslutz.com/board/showpost.php?p=1791074&postcount=13

    Eric Desart:

    "I'm not thinking that ......, official lab tests proved it did.
    Only 25% Green Glue coverage beats 100% Quiet Glue coverage. See the thread I linked.
    Hence comparing both is a simple calculation.

    The other question of course remains: Do you need Green Glue or whatever alternative at all?
    It has only sense to strengthen links in a chain, when these chains are the weak links defining the overall insulation.
    Strengtening a already strong or stronger link doesn't make the chain as a whole stronger.
    Isolation is mainly defined by the weakest link.

    And if you don't need the additional isolation, than it's lost money. Hence it depends on your goals and purpose.
    Green Glue doesn't improve a studio. Green Glue does improve TL where applied. If sensible and needed it's likely the best related product available.
    __________________
    Best Regards

    Eric Desart
    R&D Acoustician"

    ---------


    https://www.gearslutz.com/board/showpost.php?p=5330509&postcount=29

    Rod Gervias:

    "Sorry - you can use 2 layers of drywall with green glue in between for about the cost of 3 layers of drywall - and get the result of 4 layers of drywall in return."

    -------

    https://www.gearslutz.com/board/showpost.php?p=5621087&postcount=74

    Rod Gervias:

    "2 layers of 5/8" with green glue produce damned near the same isolation as 4 layers of drywall.

    Eric Desart, who is one of the leading acoustic engineers in the world (commented in this-thread early on) - and who designed the isolation systems for the quiets recording studio in the world (Galaxy) says that this product works exactly as presented by the green glue company, and worked rather extensively reviewing the test data from the company.

    He questioned Brian Ranvass for months on end as to the testing procedures used during testing, etc., etc., etc. and had samples of the material sent to him so he could perform some of his own investigations as to it's properties.

    He never once took umbrage with their testing methods.

    This is a direct quote from Eric: "Green Glue is indeed strange, very good and special."

    Understand that he will be the first to say that there are situations where green glue just would not make sense (like if you could get where you needed to be with a few sheets of drywall) - but (then again) I also say the same thing.

    I have never (for instance) used green glue on any of my large commercial projects.

    Don't use it for hotels or apartments buildings.....

    Wouldn't use it on Power Station or if I built another one of those 15,000 s.f. studios.

    In projects of that magnitude there are a lot more cost effective ways of making it from A to B........

    Power Station (for example) uses 12" thick masonry walls filled with sand to isolate it from the outside world.........

    It uses all 2x8 wall construction for the studio walls (stiffness controls the real low frequencies)....... this also makes for an air spring that is slightly deeper than you would find in a typical small studio build.

    With the movie studio we began by investing in testing SPL levels (emenating from the adjacent 4 lanes of highway) all over the property. And then located the studio in a section of the property that had SPL levels 10 dB lower than the next best place we could find. Plus we located the studio section of the building so that the dressing rooms, green room, cafeteria, make up, etc., etc. were directly between it and the highway...... another big plus. Three stories of building 40'+ thick offer a lot of isolation.

    This plus a wall assembly which included 28" of air spring, a roof with 4" of concrete on it, all made so that we had no need for any special construction.

    BUT - the average Joe in a small build cannot usually afford to build into his model this type of construction or those types of air spaces.

    Often times they are building on upper floor assemblies that just can't handle another 10 psf (of wall surface) in weight added to the floor assembly on top of what they are already doing.

    There are plenty of situations where green glue makes sense..... the fact that some people choose to bash it notwithstanding.

    Of course there is a point where I begin to question the credentials of those posters.......

    What exactly is their claim to fame - what are their credentials?

    I know Eric's (he's a friend of mine), I am well aware of Ted's, Andre's, bnapes, John Brandt's, and I am pretty certain of mine - but some of these other people posting I have never been able to find anything to indicate that they have any background whatsoever in the field...... "

    ---------


    https://www.gearslutz.com/board/showpost.php?p=13863620&postcount=4

    (This is Andre confirming Rods statement about 2x layers dw + gg = 4x layers dw, which is quoted above, and was the topic of the thread.)

    Andre Vare:

    "Compare TL-92-071 in IR 761 to the first test 0n Green Glue's test data. Rod is right.

    Andre"

    ------

    https://www.gearslutz.com/board/showpost.php?p=13866247&postcount=17

    Thomas W Bethel:

    "We used GREEN GLUE when building my mastering studio. Phenomenal product when used with the supplied directions. I can't recommend it enough. We used two sheets of 5/8" plaster board, one running horizontally and one sheet running vertically. Sheets were 12 foot long to minimize seams. The nay sayers all seem to be promoting their own acoustical products. FWIW
    __________________
    -TOM-

    Thomas W. Bethel
    Managing Director
    Acoustik Musik, Ltd.
    Oberlin, OH 44074 "

    ---------

    https://www.gearslutz.com/board/showpost.php?p=4954941&postcount=22

    This dispells the video linked a few posta ago reccomending standard adhesive instead of GG.

    Rod Gervias:

    "Standard off the shelf adhesive products will not work - when you begin gluing sheets together you effectively create a single sheet - which will NOt reat the same as 2 or more sheets using green glue.

    GREEN GLUE IS NOT GLUE.........


    Rod"


    ------

    Im sure there are more statements like that from them but those should be sufficient.

    In order to disprove the test data, and expert testimonials, data to the contrary needs to be shown. Unsubstantiated claims based on guesswork, untested assemblies, and heresay just isn't relavant.


    A leaf is a mass layer, GG is a thin film. Yes, Triple leafs are worse than double leafs of the same mass.

    Even if gg creates a triple leaf (which it doesn't is not a mass layer), the MAM resononce would be so high, it wouldn't come into play. We are talking a gap smaller than a hair? And there is no gap, its a film.

    If your logic was correct, then any layers of drywall added would cause triple, quadruple, ect leafs. And it doesnt do this.

    Data is king, im waiting for you to present some supporting your stance.

    Not sure how bickering between Eric and Ethan et al is relavant. Ethan doesn't sell GG. Ive read plenty of the bickering between them.

    And Eric supports Brian Raavina's (ugh butchered spelling) claims about GG, which Brain sells/sold, and i believe invented it.

    The US or any other country has nothing to do with it.

    Is Bert a speaker designer? Anyway he states a similar thing to the rest about GG, in the very post you linked.

    Bert:
    "And with regard to the isolation of speech and residential noise nuisance, you can do a lot with GG."

    Those bickerings are largely smart grown people acting like children, and offering slights at each other in unrelated threads due to some basic fundemental resentments.

    I don't like sales people polluting things any more than anyone else. But claims about reputable test data and topics unrelated to a person's product, need not be automatically disqualified.

    I did not use Eric's words in vain. I quoted him directly. His words are partly why i have the opinion i do of GG, they were a major contribution to my research on the topic.

    However i don't see any direct quotes of the words your claiming he said. They may exist, but they need to be seen, to be taken as true. Especially when several quotes are the opposite of what your claiming. Perhaps he changed his mind. Either way he rigorously reveiwed the data, did his own experiments, and drew the conclusions i quoted.

    Like where?

    Paul, how is the data vague? Its right there, clear as day.

    It people look at that data, the make assumptions GG will work a certain way on a non-tested/data backed assembly, that's the person's fault not GG.


    So many variables are at work in your argument here its impossible to point to GG as not working.

    Further you haven't tested these assemblies so how do you know?

    Really your claims are unsubstantiated. What is likely, is you thought green glue was going to do something it was never meant to do, and had a bad time installing it. If you presumed something other than what the data shows, that's your mistake not GG.

    I agree there is a ton of marketing begind it. But the data is there, so is the claims of at least 2 World Class studio designers.

    We are not talking matters of opinion, they are matters of fact here.

    I get its expensive, and your disatisfied. But that doesn't make the test data and assemblies untrue.

    It was either mis-application, or false expectations or maybe both.

    ? Mass follows the mass law. The gg dara speaks for itself. If i put something solid between mass that doubles the mass, i get 6db.

    What is your point here? That 10th db statement is completely nonsensical.

    Sure this is good practice for MAM assemblies.

    Unless its a data backed, tested thing like GG, or even MLV in appropriate cases.

    Random flexible stuff in between layers is never a good idea, if you want a predictable result.

    Mass, dampening, decoupling, all aid isolation.

    There is no magic, but there is tried, tested and true.

    Or just using tried and true assemblies, and the mass law, and mam calcs. Theres like 350 tested framed/drywall assemblies in ir-761. Isolation is pretty well figured out by now. And beyond that there are acoustical modeling programs.

    GG shows the effect on some tested walls. No experiments needed. But they don't seem to supply an equation, so things can be a bit grey on assemblies with no test data.

    Soundproofing company sells gg and clips and does have a series of assemblies tested, to ease guesswork.

    Yes, i believe this is true. That's why i prefer acousticians who can do architecture, like Rod.
     
  10. cyrano

    cyrano Active Member

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    What test data?

    I should disprove some data that you didn't even put forward?

    To Quote Rod Gervais (from the link you provided):

    "From a cost point of view - I've been convinced by Audio Alloy that the product is indeed a cost effective solution IF you would be willing to install 4 layers of 5/8" drywall (per side) with an isolated framing assembly.."

    Which nobody in his right mind is doing. And that's about the only case.

    Besides, from a simply practical construction pov, a four-layer construction isn't even possible, as GG isn't a glue. It will simply not fix the boards together. These will still need to be screwed, or fixed in another way, which would ruin the effect.

    GG can be an effective solution for some cases where vibrations occur in relatively light-weight constructions. It is not, however, cost-effective in studio building.

    What you misread is Eric and mr. Gervais being extremely diplomatic. Which leads to distortion of his/their expressed views. In no way does Eric say GG has any economical use in sound deadening a typical studio environment. And since we're not even talking about a building, but a wooden shed, suggesting expensive stuff like GG in such a build is economical madness.

    That's my opinion. I don't feel the need to prove anything to you. Just don't start putting words into Eric's mouth. He never supported the use of GG for typical studio problems.

    If you build a typical US office with a sturdy frame but very thin inner layers, I'm fairly certain there is a point where GG will be an economical solution for some acoustical problems. But that's not what the use is that typical fora threads advise. That's just a way to waste your money.
     
  11. kmetal

    kmetal Kyle P. Gushue Well-Known Member

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    I posted a test data plot graph a few posts above, showing the effect of the same assembly with and without GG.

    This statement shows you really have a lot to learn.

    A) 4 layer construction is in fact very possible. Screws come in lengths of 8" for construction. A 4" screw is readily available. 5/8" x4 equals 2 and 1/2 inches. 2.5 inches is far from the max depth of a screwed wall assembly. In fact I've used as many as 6x layers of dw for an iso booth.

    B) Green Glue is not an adhesive! The test data is with the drywall screwed in, as is standard construction. The screws don't ruin anything.

    Where do you come up with this stuff?

    C) remember GG cost the amount of 3 layers, and has the effect of 4. So if your statement was true (which it isnt), and 4 layers was impossible, GG would be the ONLY way to attain thr effect of 4x layers. This reinforces the argument for GG.

    A) Rod and Eric expressed their thoughts as stated by them. Injecting your spin on it is irrelevant and not fact based. They would not put thier reputation on the line if what they said wasn't true. They have no issue calling a spade a spade on other products.

    B) the OP suggested green glue, not me. I simply used facts (unlike others here) to anylize cost vs benefit.

    C) since the shed has limited weight bearing, and doesn't need alot of LF isolation, this is indeed a near perfect scenario to use or strongly consider GG. GG adds negligible weight, and performs best above 80hz.

    You can't prove it, that's why you haven't. Your talking BS.

    These are matters of fact not opinion. There is no room for opinion when there is clear scientific test data available. Your opion is incorrect. It goes against facts. And goes against expert statements, made by respected designers who have no stock in the product.

    The bottom line is GG works, as tested and is a useful product in the areas it is effective. This notion is supported by lab data, and expert testimonials (on a variety of occasions).

    Nobody is saying its appropriate for all scenarios. Particularly where space is not a concern, and LF isolation is. But that does not mean GG doesn't work as the data shows.
     
  12. kmetal

    kmetal Kyle P. Gushue Well-Known Member

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    @paulears

    I can see if you have not tested the walls, where you could draw your conclusion about GG.

    Let me explain.

    I built two nearly identical booths in the same live room, one in each corner. One used 2x6 and 3x layers dw on the inner leaf, the other 2x4 and 2x layers. Size shape sealing, all very close to each other. Full room in room. Built by the book.

    When i listen to the drum kit played between them, i cannot distinguish which booth has better isolation. There is no noticeable difference in bleed on recordings of vocal mics, even condensers, with drums playing in either booth. Both isolate very well.

    So is the third layer "not working"? Is it defying the physics. Mass law says you should get about 3db from that layer, and there is thicker insulation and deeper cavity with the 2x6 framing.

    Does this defy physics? Nope.

    Testing with a noise meter showed about 2db difference between the booths. Just a simple reading, nothing crazy. Whether testing noise outside the booths, or from inside, the trend was the same.

    The bottom line is we need to test these things and be scientific about it. Not just use our ears. This is not subjective qualitative assessment when speaking of isolation in particular. Its measureable.

    Did we "need" the 3rd layer? It was extra materials i had that's why i used it. Does the "lesser" booth work just as well in usage, yes. But that doesn't mean the 3rd layer "doesn't work" as it should. Its just not necessary in that case.

    This is what i equate to your case. The GG wasn't necessary. It does not mean the product doesn't work.

    This just illustrates the importance of proper planning, and application of materials, and the necessity for tests where they can show things we might not hear.
     
  13. paulears

    paulears Well-Known Member

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    I've looked at figures for different materials for years, and can't seem to place them in context. Bridging voids, and rigid fixing isolated surfaces does also seem to me a fact. The green glue provides a tactile, non-solid barrier, isolating one sheet from the other, and as said, the green glue turns acoustic energy into heat. My problem is also fixings. It's not the length of the screws, it's that the screws surely defeat the expensive isolation? How many required for the weight of an 8 x 4 sheet? Quite a few. The screws then provide the solid and very rigid path the glue is trying to break. I think that is a fact. Plasterboard/drywall is very heavy. The weight vertically on the screws is going to be quite a rigid contact point. The next sheet of drywall will be rigidly attached to the screws too. These things get glossed over.

    We talk about XdB for a sheet of material, but we punch holes in it for services - how many dB is a hole for power, when sealed with caulk - acoustic or decorating? Spend a fortune on green glue and the screws and 'holes' compromise whatever it does. I also cannot get my A Level physics around the energy conversion from rigid panels. It works for membrane absorbers, because they physically are made from deformable materials - they're designed to flex. Drywall is designed to be rigid. How does the energy conversion work with stiff, or even virtually rigid materials. It has to be tiny. The spec suggest a lot of energy is being removed from the path from inside to out. Sorry - but I have to remain a sceptic.
     
  14. kmetal

    kmetal Kyle P. Gushue Well-Known Member

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    No Paul, the screws are actually necessary for GG to work. It squishes it into one uniform film, instead of the lines and grid it is when applying it.

    The test data is WITH screws. So any effect they have is shown, in the test.

    Right, this is feild vs lab. But that doesn't mean GG doesn't work. Just like drywall doesnt stop working under these cases.

    Ditto for drywall, windows, hvac ect. There are compromises. It doesn't mean gg doesn't work, it simply means your compromising a structure with better TL than would be without it. Starting higher on the rung.

    Bang your hand (or my head lol) on a drywall wall. Does it vibrate? Yes. Do the same on concrete, or a driveway.

    Part of the reason dw walls have a weakness below a critical frequency, is because they vibrate most at that critical frequency. If they were infinitely rigid they would have no resonant frequency.

    Earth dampened concrete, like a slab has effectively no resonant frequency. It is also one of the best sound isolators we know of.

    Whether your skeptical or not, the facts are there, and have not been disproven. Despite many offerings of opinions, no real evidence says anything to the contrary.

    Its important to express that your using opinion and subjective anecdotal evidence, so a person looking for truth and advice can consider that grain of salt. It doesn't make your account less valuable, but your account doesn't prove anything from a scientific sense. It doesn't make the gg tests false.

    If anything your account reinforces dilligence. To not use unecessary techniques. To align one's expectations with available data.
     
  15. kmetal

    kmetal Kyle P. Gushue Well-Known Member

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    For the record, in the last 12 years, ive done 10 design/builds in person. Only 1 project i reccomend GG. This was where ceiling height and load were a limitation, and isolation needed to be maximized.
     
  16. paulears

    paulears Well-Known Member

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    I appreciate the information. Clearly, we're rather like our Government making decisions based on science. The snag is there are variables, and I simply am floating between opposing science, and of course we all have our own take on it. I suspect I'll continue to add layers if there is space and have a good think if there isn't.

    Based on the declared chemical components, one thing is for certain - it's overpriced. That extra layer of sheet looks damn attractive by comparison.

    How would sitting the layers on neoprene at the bottom to take the weight and then more neoprene between the inner sheet and the stud? This would seem to be a cheaper and equally effective way to do what the green glue does? You could reduce the screw count, improving isolation too. If you could manage it, you could even only use the neoprene where the screws go, reducing contact area even more?

    Next job is to sell all the unused strip and iso mounts. Need to search the net for the most optimistic dB figures for it, and quote that in the advert, rather than the more accurate, but less exciting ones on other web sites for what appears to be the same product, bar the name.
     
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  17. kmetal

    kmetal Kyle P. Gushue Well-Known Member

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    More mass layers is probably the best bang for the buck. That's why 5/8 dw is the standard for studios on this side of the pond.

    Im not sure neoprene would convert vibration to heat like gg. I just stick with tried and true assemblies, like pictured in rods book, or tested in the IRC data bank. Then i just add mass as needed because its simple to estimate.

    If you look at screws from a mass perspective, they surely weigh more than the drywall dust they are displacing in the hole. Screw add mass. When they couple dw to studs they add dampening, ridgity. Otherwise the dw would flop around.

    You just wanna hit the studs. Any sound thru a screw hole would need to travel thru the stud. Which often is a strong point since the studs add mass to that area.

    Beyond that the screw holes get mudded over. So they are sealed, and a tiny bit of mass added.

    Since any wall assembly is tested with screws and the amount required by code/manufacturer, we can be sure they are a non issue.

    Rods book has isolation ratings for RC channel and RISC1 clips. If you need it i can PM a screenshot from the book, to include in your add.

    If acoustics made sense it wouldn't be nearly as interesting!!! Lol
     
  18. paulears

    paulears Well-Known Member

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    Indeed - I've had Rod's book for a long time - full of useful stuff, and good use of theory. I just wish I trusted the GG data, and frankly I don't, and because it's a middle process, few people would ever do a room, then redo it and publish the results. I suspect the figures are extrapolated data - you measure baselines, you measure the relative densities and then you predict results based on the science. This has been a flawed technique many times. The original data is sound. The test methodology is sound, the results look good. The practice is flawed. If you plot sound absorption in a space using spot frequencies, you get a straight line, or perhaps a classic bell curve, but that huge resonance at 234.5Hz is missing, and that strange suck out at a certain frequency is absent too. That's the problem with interpolating test results. In my local builders merchants you can get plasterboard with sound proofing properties - which seem to be a 'clever surface' and special gypsum. The advertising is pretty vague. https://www.insulationexpress.co.uk...8c-hTt2wMamLUzzY_O7Di5E5oLRulvs4aApn2EALw_wcB
     
  19. kmetal

    kmetal Kyle P. Gushue Well-Known Member

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    Ugh those "specialized" gypsums almost never have a justifyable place.

    Its true things can get get glossed over in test data. You notice GG tests dont go below 80hz, but many of the IRC tests go to 50hz. IRC also states the values in a table. Those graphs make it hard to discern a db or 2 difference.

    STC ratings get quoted all the time in acoustical advertising, yet it doesn't dip below 125hz. And is a sort of weighted averaged response. Assemblies can have the same or greater STC rating, while performing worse at sub 125hz.

    Green Glue does notate when they are using actual measured results and estimates, i appreciate that transparency.

    DIY changes the cost benefit of GG. Paying a drywall hanger, taper, buying the dw, screws, and caulking, paying someone to caulk things, adds up. That's where GG can be cheaper than the 4x drywall layers.

    When not paying for labour that changes the value proposition.
     
  20. kmetal

    kmetal Kyle P. Gushue Well-Known Member

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    This is Rods cost breakdown from a real project. It was from 2006, and in the sos forum i linked in other posts.

    Eric Desart wrote:Rod,

    Can you translate that in numbers?
    How much cost applying GG per surface unit (sft or m2) per glued layer versus not gluing. (hence the absolute added cost). Since you calculated it for a project, you must have a good picture.

    1 Material (base on which cost per material unit = prices maybe differ per geographical area)
    2 Labor (in cost and average time = hourly rates can differ geographically).

    3 Total

    Eric,
    ------



    Rod:

    Sure can - understand that these numbers are what I currently pay on projects - the Green Glue Labor Cost is what was paid for this project in New Jersey, I do not have time breakouts for these numbers, seeing as I am not a contractor - I only care about the bottom line and do not track such things.

    Cost Unit
    Base layer of 5/8" drywall - material and labor 0.90 sf
    Material Costs - .39 sf - Labor .51

    Finished Layer of 5/8" drywall M & Labor 1.50 sf
    Material Costs .46 sf - Labor 1.04

    green glue materials 0.93 sf
    Green Gllue Labor 0.43 sf

    Costs per sq foot for a 4 layer drywall 4.20 sf
    application (3 base and one finished)
    Cost Per Square Foot for 2 layers Gyp DW + GG 3.76 sf
    1 base - green glue and one finished)

    Cost Savings per square foot 0.44 sf

    Note: the average cost for fully adheared drywall systems only adds .16 per sq ft

    Note that things change if one is doing this strictly as a DIY project - if you pull out the labor numbers - the cost for a 4 sheet drywall project is 1.63 per sq. foot - while you will pay 1.78 per sq foot for green glue with a 2 sheet job.

    BUT - as I noted - you actually get more bang for the buck with the green glue in mid and higher frequencies - and a sligh advantage around 100Hz (I would guess based on the trend I see in the testing that frequencies below 100Hz would benifit as well) which to me is worth the added cost of .15 for a DIY project.

    I hope this helps.

    Sincerely,

    Rod
     
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