Economy Isolation booth / chamber

So, this is more a soundproofing question in general rather than a theater build question (though blocking out TVs and stereos, among other things, would certainly be a part of the end result), however I don’t want to ask soundproofers, as they will of course be a little biased, and it’s difficult to separate ******** when people are typically in the business of making it difficult to separate when a lie is in their best interest. ANY WHO… my question pertains to an isolation chamber for sleeping and perhaps working in, similar to a Sleepbox (www.sleepbox.com) but smaller and less expensive without the bells and whistles.

Due to the nature of my, shall we call them “sensitivity issues”, I have done a fairly decent amount of research on soundproofing. So at first, I figured that a diy cheap iso sleeping/working chamber for use in most houses or apartments for myself and others in my, ehh… ’support group’ (we all need support sometimes) wouldn’t be all that difficult to design; unfortunately, the water-filled lead coffin from "Dare Devil" is not feasible here.

However, there is one huge obstacle: weight. Even if I built, for example, an 8’x6’x4’ chamber with panels made of 3 layers of ¼” cement board in a CLD with damping glue, that would still equal the total weight of a 3’ x 5’ x 9” piece of concrete (seems a little heavy for your average 2”x6” floor framing in most places).
The next biggest obstacle is that in most cases, the panels would have to be fairly thin so as not to take up even more space than the thing already would. And since a 2”x4”xhowevermany’ panel may be too much in many cases, and would have a large LF resonance anyway, I almost feel better about doing without any air-gap at all.

My thinking is: Use any mass I add to maximum effectiveness. As such, damping would be the key focus, and I would have to go with light gypsum board rather than concrete. Using 3 layers of 3/8” (as opposed to 2 layers of 5/8 in fire grade stuff in order to take full advantage of lots of damping, though the expense would be a good deal higher) in CLD with maximum amount of damping glue and screwed to a 2x2” frame seems like about the best I could get away with, plus it shouldn’t be too difficult to move around. The frame would face toward the bed and could have the recesses it creates on the panel filled with an open-celled foam for better HF TL as well as attenuating noise within the chamber. Since damping glues seem to work best with medium to high frequency, and the absence of air-gap would limit the LF transmission (though to certainly not to a very large extent, due to lack of mass), it seems about as good as I can get. If the primary issue for an individual case was medium/high frequency, I would probably recommend an air-gap with 2x4” sills with staggered 2x2” studs.

So, the basic design would be a box containing a bed, a short thin weather-stripped door cut to fit (solid I would imagine with a foam matt attached to the side facing the bed), a hole in the wall with a small fan for ventilation (fan would provide white noise as well), a light and light switch, and perhaps an outlet. The bottom of the box would be a CLD with two layers of 1/2” OSB onto which the panels are screwed, with the OSB being propped up off of the floor of the room with neoprene isolating pads. And don’t talk to me about earplugs, buds, over-the-ear muffs/phones, or active noise cancelling; I know of that stuff well and they’re not the topic of discussion here. Also, part of the idea is to create a design which is easy to build with a few simple tools and fairly reasonable cost wise. Barring cost though, it might be interesting to see how well two full sheets of Quietrock adhered together with damping glue might work (3 layers of damping; minimum thickness and weight). Sorry for the short story, but I figure it's best to be thorough.

Is nobody going to answer? It's kinda important...

I suppose I'm still having some difficulty understanding damping; the glues are supposed to absorb kinetic energy and convert it to heat through internal friction, but the effectiveness of this is dependent on the mass? That is to say, the same degree of damping wouldn't increase a lighter wall's and a heavier wall's decibel reduction by the same value? That's kind of the impression I get when you're talking about decoupling or damping a mass. If the goal of damping is to bring the TL closer to the mass law prediction, then it seems like damping a wall would lower the low frequency reduction, since that's usually higher than the mass law prediction.

Ok I get your point; but just to be sure that I understand: The effect of damping is reletive to the mass of the wall; for a wall made of lighter material, the same total amount of damping used will have a lesser db reduction.

uhh... I don't think I'm explaining this correctly. I understand that damping is less important than mass, but what I'm currious about is HOW the damping works. Say that we have two walls of similar construction, with layered wallboard of similar stiffness, but different densities, and thus, mass. The same total quantity of damping is then added between layers for both walls. Considering that all other variables are the same, would the damping improve the reduction of BOTH walls by, say for example, 8 points, if one wall had an stc of something like 35, and the heavier one had an stc of 40? Or would the increase be lower for the lighter wall?

The reason why I'm asking is because if damping with these glues works by converting sound into heat, than it seems like it's effects would be (mostly) independent of mass, so long as there is enough rigidity to create the CLD; is there something else going on here that I don't understand?

But what about density as it relates to stiffness? I've read some papers here and there that have to do with visoelastic damping in general, and a big emphasis is on stiffness; obviously a soft material would not operate very well in a CLD construction, so the more stiff the constraining materials are, the better they seem to work. Since increased density usually though not always equates to increased stiffness, I can see how a heavier material or just a thicker material of the same type (increased thickness= increased stiffness) would also generally work better in a CLD. That being said, theoretically, could a lighter but much stiffer constraining material potentially have similar soundproofing properties?

Well, that doesn't make me feel a little like crap. I was just asking a question because I want to understand; I'm not an acoustical expert, never claimed to be, and I never really even made any assertions... being analytical is something that everyone should be, and I don't know why people always get upset with me for it. Perhaps the stiffness thing was true, but we don’t have the technology/materials for it, so we use mass; I don’t freaking know, I was just asking. I feel like I have to apologize for myself before I say anything sometimes.
Edited by misophonia - 9/25/12 at 6:53pm

Thanks jours. And thanks to ted as well for helping to 'enlighten' me; I don't mean to be all touchy feely, I just get tired of being misunderstood when I honestly try to come across correctly (jautor, I was just asking questions and it seemed like he thought I might be arguing with him or something). Certain… ‘individuals’ at supersoundproofing forum also told me I was “reinventing the wheel”, because I try to think of ways to soundproof in difficult situations with what little knowledge I have; sometimes the info you need is difficult to find, which is why I started this thread. All I can do is ask questions.

Black and White may or may not be the correct way to say that you guys can take a rather hard-lined approach; I'm well aware that this half@$$ed sleeping/working booth may not be even half as good as a double leaf wall plus damping, with a one-foot-thick double stud walled air-gap filled to the brim with cellulose and caulked like a sum-b*tch... But just the same, any kind of reduction would be better than nothing, plus the fact that if the booth contained a white noise machine of some sort, it might just be enough.

My point is: I'm not trying to build the bat cave. Considering that the weight is the prime issue, is what I purposed the best way to use the weight to maximum effectiveness, and what kind of reduction am I looking at being able to gain? If people are looking primarily at medium to high frequency, is it best to replace a layer of damping for an air-gap, no matter if it is even a couple of inches?

Also, on that note, there is something else that I've not been able to get a concrete answer for so far: Does the air-gap convert HF into LF, or does the air-gap simply have a greater weakness for LF, and why? I know that the wall acts rather like a bass drum, and though I've done some research on bass drums, I still can't find the damned info that I'm looking for.

Ok, sooo here’s what I’ve read: the HF coincidence dip is from the bending of sound waves, and the LF resonance point is from standing waves within a wall cavity; is this correct?