how do you guys feel about this

http://www.soundprooffoam.com/soundproo ... -good.html just curious, as it may be my only option for dealing with one wall that may be an issue.

I noticed the page "Why buy from us?" came up as a dead link. :?

I didn't mean specifically this brand or anything, I was wondering more about the idea of retro-fitting a wall to be a little more sound resistant and whether or not it would be decent or rubbish. I'm not looking for complete blockage I just want to be able to strum some acoustic guitar and sing without annoying the neighbors at the later hours.

Hi Ian. That place you linked to shows an excellent construction method for creating a three-leaf wall!!! That's a really, really bad idea... Three-leaf construction will, of course, make your isolation WORSE than it is already at the low end of the spectrum, and only improve the high end. That does not sound intuitive, since you think you are adding more mass to the wall, but in fact you are also re-tuning the resonant frequency of the entire wall to a higher frequency, and skewing the transmission loss curve, so at the lower end of the spectrum the wall will now transmit sound BETTER than it did before. It will only isolate better at high frequencies. You would be better off just adding the extra layer of drywall directly on top of the existing drywall, with Green Glue in between, and probably for about the same overall price. But even better would be to take off the existing drywall, put resilient channel across the existing studs, full the gap with mineral wool, then put the drywall back on again, then put another layer of drywall on top of that, once again with Green Glue sandwiched in between. However, that only treats one wall: you probably also have issues with your ceiling, floor and other walls. They will probably need similar treatment. Just treating one wall won't help much if sound is flanking around that wall through the ceiling or floor, for example, which it most likely is. You will probably also have issues with windows that you'll need to think about. - Stuart -

I don't understand how just drywall would be better than drywall, plus that dense material. could you link me to something explaining this if you have a reference? also, I cant just go about gluing extra drywall on, its an apartment building, and I HIGHLY doubt the landlord would be ok with it. The method I linked too is all attached to wooden strips which could just be unscrewed when I eventually move out. I'm only going to be at my current location for about two years.

I don't understand how just drywall would be better than drywall, plus that dense material. could you link me to something explaining this if you have a reference?

I didn't say "just add mass" I said "add mass plus Green Glue"! Big difference :) Green glue is not an adhesive: it is a special acoustic polymer that has been proven to have excellent sound isolation properties. Unlike the secretive manufacturers of that product that you linked to, the manufacturers of Green Glue have had their product actually tested by independent acoustical laboratories, and have published all of the results of those tests. It works, and works well. Next: It's not just the issue of the additional mass, but rather the issue of the air gap that you create between the new mass and the existing mass. This is a simple principle of physics: By adding a layer of mass over an air gap, you create a resonant system, which is implicitly coupled to (and part of) the existing resonant system behind it (the existing wall). Your new addition changes the resonant frequency of the entire system, driving it up, which is always a bad thing for low frequency sound isolation. It's good for high frequencies (speech), bad for low frequencies (music). That material that you linked to looks an awful lot like MLV (mass loaded vinyl) or something similar, but the manufacturer is very careful to NOT specify what it is made of, except to say that it is "acrylic". Perhaps because of the bad rap that MLV gets on places like this forum. He also does not publish an tests done on his product by independent labs. I wonder why? MLV is just mass, as is drywall. Mass is mass. Sound waves don't care if you make 100 kg layer of mass from bricks, MLV, wood, concrete, drywall or lead plate. It is all the same for the sound waves. They are not picky, and won't bother checking for the manufacturer's logo on their way through. They will react in exactly the same way to any kind of mass. Higher density helps from the point of view of space, since you can get more mass into less volume, but mass is what stops sound, not what the mass is made of. Sound waves don't care if you paid US$ 50 for the mass, or US$ 500, or US$ 5,000, or even US$ 50,000 for some exotic extremely dense material. They just see "mass", and that is what stops them. The issue is that, while MLV undoubtedly is mass, it is really EXPENSIVE mass! So if you have money to waste, then by all means, go ahead and buy it! But do realize that you could get the exact same mount of mass from another sheet of drywall, and also that by mounting ANY mass over an air space you have created a resonant system. On the other hand, if money is important to you, then drywall is really CHEAP mass, and is easy to install and work with. :) But to answer your original question: Mass law states that each time you double the mass of a sound barrier, you improve its transmission loss by 6 db across the entire spectrum. So just adding mass to the existing wall will improve the isolation by 6dB, regardless of what the mass is: If it is drywall with Green Glue underneath it, then you will get much better than that. But if you put an air gap underneath it, then physics says that you have raised the resonant frequency of the system, tilted the transmission loss response curve, and thus lowered low frequency isolation. You can compensate for that, but in order to do so you need... more mass! You can't trick the laws of physics.

also, I cant just go about gluing extra drywall on,

But you can build a new frame, screw that to the existing wall, then attache rolls of MLV to it, then attach more drywall anyway? Strange landlord that you have! :) But I didn't say that you should glue it on. I said that you should attach it to the existing wall, with Green Glue in between. Green Glue is not glue. It is an acoustic polymer compound, specifically designed to improve isolation of low frequencies when used between layers of drywall, and proven to be very effective. But you cannot use it to glue the drywall. You still need to nail it or screw it in place.

its an apartment building, and I HIGHLY doubt the landlord would be ok with it. The method I linked too is all attached to wooden strips which could just be unscrewed

How would the landlord even know that there was an extra layer of drywall on the wall? The landlord would have to get out a tape measure and check the dimensions of the room in order to figure out that it is five eighths of an inch smaller.... I assume you do plan to paint it after you hang it, no? Or were you planing to just leave bare drywall up there, attached to your new frame which is attached to the existing wall, and leave it all like that, bare and visible, screws, wood framing, and all? If you paint it to match the rest of the room, then there is no way the landlord would ever know, without a tape measure. For information on these principles, the best you can do is to get "Master Handbook of Acoustics" by F. Alton Everest, and also "home recording Studio: Build It Like The Pros" by Rod Gervais. - Stuart -

thanks a lot for the detailed response. I've read about green glue but I always thought it was an actual glue... so I'm thinking about doing this(adding drywall), it sounds like a pretty good deal, but the added low frequency pass through worries me a little bit. and 6 db seems like almost nothing to me though so I'm wondering if its even worth it. I think if i could manage to cut out about 15 db then that would definitely be worth it. I was playing with my stereo receiver and going from -55 db to -70 db really makes a difference in terms of killing the sound. going from -55 to -61 on the other hand is a barely audible difference. EDIT! -------- I cant build an attached wall, so I think I'm going to go the route of a movable iso wall-type thing

and 6 db seems like almost nothing to me though so I'm wondering if its even worth it.

Bingo! :) That's the point I was trying to make. Mass law alone does not do much for you. You need a LOT of mass before you start getting substantial benefits. Which is why Green Glue is such a useful product. In fact, to get that 6 db increase, you need to double the mass. So since your wall already has one layer of drywall on each side (one layer on your side, one on the neighbor's side, you'd need to add TWO layers of drywall to get that 6 dB gain, which is definitely not worth the effort, or adding four extra layers will get you 12 dB. In other words, if all you use is drywall that it is not worth the effort, just like you said. However, Green Glue changes that. Adding just ONE layer of drywall with Green Glue in between, will get you 12 dB already (instead of about 4 dB). Two layers of drywall with GG will get you the 15 dB that you mentioned as being reasonable, based on your "knob twiddling test". To give you a better idea of the problem you wold be creating by following the instructions on that web site you linked to originally, here is some information on the reason why triple-leaf construction is such a bad idea, and some real-world graphs showing actual test results. The data comes from the National Research Council of Canada. http://www.greengluecompany.com/underst ... leLeaf.php Interesting reading! Take a look at the graph at the bottom of the page. The black line shows the high isolation you get from a good two-leaf wall. The green line shows just how much that changes if you make it into a three-leaf wall by adding more mass over a thin air gap. Their final comment summarizes it nicely: "Triple leaf ... constructions should be avoided like the plague. You will always get a lower level of sound isolation, and this loss may be most severe where you need performance the most – low frequencies." If you look at the diagrams of how those walls were built that gave the results shown in the graph, you will notice that the worst-case graph (green line) is for a wall built exactly like they tell you to on that web site you linked to. Like I said originally, following that advise would lead you to disaster! - Stuart -

I cant build an attached wall, so I think I'm going to go the route of a movable iso wall-type thing

I'm not sure what you mean by that. If it is movable, I don't see how you could seal it, and if you don't seal it, then it cannot isolate. Could you explain in more detail what you have in mind? - Stuart -

if people use gobos for isolating drums, im assuming you could isolate anything...no? obviously it wont completely isolate, but it should drastically cut down.

I know you said you can't build a wall. But they wont notice the new wall got a few inches closer. Or The land lord a might appreciate the sound isolation and give you a rent discount and/or pay for the construction :lol: :roll: take off drywall on your side. beef up inside studs with a layer or 2 of 5/8 drywall and seal. (it would be waaaaayyy easier if the neighbours would let you on their side to hang full sheets over their wall) addin' the beef is tiedious work fill with insulation hang resiliant channel across studs to decouople your side. hang 2 or 3 layers of drywall on the resiliant channel and seal. (green glue if desired.) That'll take care of your wall transmission fairly cost effectively. And the room will lose the depth of the resiliant channel plus you drywall layers. (~1 1/2 ")