Oh brother! Where to start?
I'm sure you picked up on all of the myths, mysteries and half-truths in there, Brien, but the ones I noticed include:
- "Soundproofing" (What does that even mean, anyway?)
- "Cavity insulation doesn't work" (it does when you do it correctly...)
- "Starting with bare studs, we place sound-blocking insulation in the stud cavities" (Whoa! I though you just said that cavity insulation doesn't work? But now you start out with cavity insulation? Ummmm.....)
- "and have the same soundproofing value. " (What is "soundproofing value"? What units do you describe that with, and how do you measure it? I've never heard of such a thing in any acoustic paper I've ever read, so I guess this must be a new invention?)
- "It prevents sound from echoing around inside the stud bay, and it slows down the sound wave." (Really? And your references for these new acoustic discoveries would be ...?)
- "The next layer is the sound barrier—a heavy, black "mass-loaded vinyl" (MLV) membrane." (
Nuff said... Why do people still insist on promoting such hugely expensive, very cost ineffective "solutions"? Do the words "profit margin" have anything to do with the answer?)
- "Applying a 130-pound roll of Sound Barrier is heavy work for the crew. Obviously it's even more work to roll it out across a ceiling (see photo) than onto the wall. We've been working on various rigs and jigs to solve this problem," (Duh! Really? How about another suggestion: Don't use it at all! Instead, design and build the wall correctly, then you won't need the hugely expensive, hugely heavy, hugely hard to install MLV)
_ "The next component in this assembly is drywall furring composed of clips and hat channel." (Finally they got something right! Now if only they'd learn to use it correctly, without creating thin resonant cavities right under the wall surface...)
- " It also creates an air space between the drywall and the MLV sound barrier" (No kidding! And that is also know as a "resonant cavity": Not something that most people would want inside their walls, undamped, just below a thin, flexible, light-weight drywall surface.......)
- "We use two layers of 3/8-inch drywall " (
You gotta be kidding me??? only 3/8"??? No wonder they also need MLV! Maybe someone should tell them about mass law, thin panel resonance, and show the the equations for two-leaf resonance, 3-leaf resonance, and membrane trap resonance...)
- "laminated together with Green Glue, a viscous elastic adhesive." (So they are using products that they don't even understand, and haven't even read the instructions for? Since when is Green Glue an "adhesive"? Since when can it be used to "laminate" drywall? Does Green Glue Company know that their product is being misused and misrepresented like this? )
- " You can also buy the sound-deadening drywall already laid up, under the brand name QuietRock. We use regular drywall and Green Glue because it costs less than QuietRock for basically the same thing." (No it isn't. QuietRock does not use GreenGlue, as far as I know. Unless they changed they way they manufacture it=
- "The mass of the drywall deadens the energy of the sound waves that make it that far, while the viscoelastic adhesive absorbs even more sound energy and decouples the two layers of drywall from each other." (Really? So THAT'S how it works! And here's me all these years believing that mass does not absorb energy and that Green Glue does not work by decoupling... )
... That's as far as I got, before I gave up. Does anyone else think that maybe leaving out the MLV, filling the entire cavity with 703, and using 2-layers of 5/8" drywall plus GG, instead of all the rest, would do a much better job, be easier to build, faster, and work out much cheaper for the customer?
sheesh...
- Stuart -