Corner treatments

I would like some thoughts on the differences between "corner treatments". What are the differences when treating room corners with "superchunks" (triangular pieces of insulation from floor to ceiling covered by fabric) and the corner "bass traps" that are sold by companies such as Auralex (corner shaped foam acoustical tiles)? What are the pros and cons of each? Thanks.

What are the differences when treating room corners with "superchunks" (triangular pieces of insulation from floor to ceiling covered by fabric) and the corner "bass traps" that are sold by companies such as Auralex (corner shaped foam acoustical tiles)?

You might find this thread helpful, from over at the StudioTips forum: http://forum.studiotips.com/viewtopic.p ... foam#p3975 And this one too: http://forum.studiotips.com/viewtopic.p ... foam#p3969 As you can see, there's not much in it when comparing superchunks to commercial foam traps. They both work roughly the same, with only minor differences. - Stuart -

Thanks for the response and the links. Another question while I plan, if you will kindly allow: How much space is acceptable between two-leaf walls in order to maintain the two-leaf properties? As an example, If I were to have a 4' - 5' wide hallway between two seperate two-leaf systems, would it counteract the two-leaf systems and become a four-leaf? 2 layers of drywall ___________ Studs and Insulation ~~~~~~~~ air space 2"-3" Studs and Insulation ~~~~~~~~ 2 layers of drywall ___________ 4' hallway 2 layers of drywall ___________ Studs and Insulation ~~~~~~~~ air space 2"-3" Studs and Insulation ~~~~~~~~ 2 layers of drywall ___________ Does that make sense? :shock:

I asked that exact same question several years back, and it took me a loooong time to figure out the answer! So here it is: The way to think of MSM walls is as tuned systems. They are tuned to a specific frequency at which they resonate wonderfully, and therefore also transmit sound wonderfully, but they block sound above about 1.4 times the resonant frequency, and block it well above about twice the resonant frequency. So obviously the idea is to tune that frequency as low as possible, lower than the lowest frequency that you need to isolate. The way you tune them, is with mass and air gap. More mass=lower frequency. Bigger gap=lower frequency. The bare minimum recommendation is 4" (10cm) gap, and one layer of 5/8 (16mm) fire-rated drywall on each side, and fill the gap with insulation. That will tune the wall to about 39 Hz, so it will only isolate well above 78 Hz. Change to 6" (15cm) and two layers of drywall on each side, and now you have resonance at 23 hz, with good isolation above 45 Hz. In your case, you say each of your walls only has a 2" to 3" air gap (so I guess you must be building inside out walls? otherwise there's no way you can get such a small gap, since 2x4 studs themselves are 3-1/2 deep), and if that's the case then you are in pretty much the same place as for the 4" wall with one layer: resonance at 39 Hz, decent isolation above 78 Hz. In fact, that's a general, very rough rule of thumb: if you double the mass you can halve the distance for the same resonance, and vice versa: double the distance you can halve the mass. The relationship is very roughly linear, down to about 4" gap and the surface density of one layer of drywall. Now, if you add another leaf (or two, as in your question), then you re-tune the entire system to a much higher frequency. In fact, you tune it to TWO fundamental frequencies in the case of a 3-leaf wall, and THREE fundamental frequencies in the case of 4 leaf, and all of those will be higher than the equivalent frequency for the same total mass and distance with a two-leaf wall. However, for very large gaps, the frequency is so low, and the effect is so small as to not be worth worrying about. With a 4 foot gap, if that were just a two-leaf wall with the same mass, then it would be tuned to 7.8 Hz with no insulation (5.6 Hz with), and would therefore isolate well from 15.7 Hz without insulation, or 11.2 Hz with insulation. If it were 3-leaf with two gaps of 2 feet each, then it would still be fine: F+ would be 14.6 Hz, and F- would be 10.35 Hz without insulation, or 10.5 Hz and 7.4 Hz with insulation, so it would still isolate darn well for all frequencies above about 20 Hz. (I can't fine my equation for 4-leaf, but it wouldn't be a lot different.) In other words, if there is a very large gap in the wall somewhere, and a decent amount of mass on all leaves, then 3-leaf and 4-leaf are no longer so scary. The real issue with multi-leaf walls is when the air gaps are small (just a couple of inches), and the leaf itself is light weight, which is what happens when someone has an existing 2-leaf wall that isn't isolating well (such as a typical house wall), then attaches battens to that and puts 1/2" drywall on them: Then they wonder why the wall now isolates even worse for low frequencies... OK, so that's a very long convoluted way of saying: with your 4 foot corridor, you are fine. Don't sweat it. That said, your diagram does not match your numbers! If you have "drywall-stud-gap-stud-drywall" then the air gap cannot possibly be just 2" to 3" inches! The studs themselves are 3-1/2" deep at least, and you need to leave at least a 1/2 separation between the two frames, so your total air gap must be at least 7-1/2".... Maybe you forgot to consider the depth of the studs in your "air gap" number? If you are talking about a separation between the frames of 2" to 3", then your total air gap is 9" to 10", which is great. That would give you a fundamental resonance of 17.2 Hz (assuming the entire air gap has insulation in it), and good isolation above 34 Hz. Hope that helps! - Stuart -

:shock: DOH! I failed to add the width of the 2x4 that is attached to the concrete. My "diagram" is the correct one to reference. The air gap I was mentioning is 2"-3" between the studs, not between the drywall. Nice catch! Ok, so since we know that the hallway (which is 4-5' wide) between the walls is a good thing, what if the walls on either side of the hallway were only standard walls such as: Drywall _________ Stud/Insullation ~~~~~~~ Drywall _________ 4-5' Hallway Space Drywall _________ Stud/Insullation ~~~~~~~ Drywall _________ Would this still give me an acceptable result while saving space and material (and therefore $$)?

Would this still give me an acceptable result while saving space and material (and therefore $$)?

Probably not: ordinary walls built like that are fully coupled: any sound hitting the drywall on one side will make that drywall vibrate, thus making the stud itself vibrate, and therefore also vibrating the drywall on the other side, since they are all tied together, mechanically. You'd be lucky to get 30 dB of isolation out of a normal house wall. The wall you described previously (double stud frame, 2 layers on each frame, 10" gap) is roughly ten thousand times better, literally: Done right, it could theoretically give you a total of 70 dB of isolation, which is 40 dB better than a house wall. And a 40 dB difference in SPL does, indeed, imply a factor of 10,000 times less energy getting through the wall. The gap, the decoupling, and the extra mass makes a huge difference... ! :) So I'd go for the ten-thousand-times-better-wall, I think.... :) The big question is: how much isolation do you need? While it would be nice to have two 70-dB walls between you and "them", do you really need that? You could save money by not over-building. Also, once you get up to such high degrees of isolation, the wall stops being the major factor, and things like doors, windows, HVAC, electrical system, and flanking start becoming the big issues. Getting a door to isolate to 70 dB is a real tall order... ! So it's better to look at your studio as an entire system, and set your goals realistically, in terms of how much isolation you really NEED, not how much it would be super-cool to have. It also makes no sense to over-build one part, since it is the weakest part the defines the total isolation. So a 70 dB wall with a 60 dB ceiling and a 50 dB door means that your isolation is 50 dB. Which implies that you wasted money getting the walls to 70 dB and the ceiling to 60. There are many ways to save money by designing the whole thing to do the job right, neither too much nor too little. - Stuart -

Ok, thanks again, master. To go further down the rabbit hole, let's say that the scenario is the second example that I posted (standard walls with a 4-5' hallway between). Would it be more beneficial to have only one layer of drywall on each wall and use a cloth rather than drywall on one side of each wall? Such as: Drywall . ___________ Studs/Inusalation ~~~~~~~~ Cloth . ------------- 4-5' Hallway Cloth . ------------ Studs/Insulation ~~~~~~~~ Drywall . ___________

To go further down the rabbit hole,...

Why didn't Morpheus have a green pill too? :) Or at least some "eat me" cake, to make things more interesting... :) Theoretically, what you describe would, indeed, be a two-leaf wall with a very deep air gap, but it wouldn't work the way you are hoping. You would have to seal that corridor air-tight and also eliminate all other flanking paths, in order to make that work. That would be hard to do, I reckon! Also, that hypothetical "wall" is only one part of the entire room isolation system. In order for it to work the way you hope, you would have to have similar "corridors" on other fives sides of the room. In other words, the room itself would have to be suspended somehow in the middle of an empty spade with five feet of separation on all six sides... Hard to see how that could be accomplished! It might help if you were to provide the full details of what you are trying to achieve, here. You can't isolate a room on only one side anyway, so if that's what you were planning, it ain't gonna work, sad to say. If you are just trying to stop sound getting across that corridor from room "A" to room "B", then your approach so far is not going to achieve that. Sound will simply take another, easier path around your corridor, ignoring it as though it did not exist. If you do a model in SketchUp of what your situation is, and explain what you want to achieve, it would be much easier to offer useful advice! - Stuart -

Ceiling clouds, especially used to treat high ceilings, are generally suspended from the ceiling and act as a barrier to absorb and contain the sound.

Really???? :shock: :D :shot: :lol: Just wondering here, but how do you hang a ceiling cloud in a "soundproof" mobile recording van with 7'4" ceilings??? - Stuart -