The main projects are
1) the second ceiling
2) a complete and decoupled 2x4 wall shell built inside the existing plaster walls..which are in very good condition and furred to the brick of the building..so, not insulated but thick, at least an inch...
Actually, that's not the best way of approaching it. You mention those as if they were two different things, but in reality they go together. I'll get back to that later, but this is a big issue... bigger than you think.
4) I am also going to try to isolate where walls meet floor and try to decouple the flooring,
Same as above... more comment below... but first, what is the floor right now? Is that a concrete slab? Is it mostly slab-on-grade? You mention a basement, but does that run under the full size of the floor? Or only partly? Anything else down there?
Thank you, Stuart! Excellent post and appreciated..
that's what we are here for!
Yes, large room..I play rock and roll from loudish to fairly low key..I write and record with a friend for one..Also record demos with a local acoustic and electric players..folk, easy rock, raunchy rock..but not in your face or metal stuff..Sometimes some horns and and a violin, ukelele, cello or three.
OK, so all sorts of genres, with all sorts of levels, up to maybe 115 dBC or so.
As for the timeline of this...The room is stripped clean right now, it is a construction site. There is no treatment up, , Just tool stations and myself..
Photos would be useful....
BTW, im experienced and realistic and experienced enough to understand that sound is gonna get out, even with some extra mass and basic de-coupling..even with a lot of mass.. im gonna piss someone off at some time..
That is, indeed, the common situation... However, it doesn't
have to be like that, if you design it right and build it right... It is quite possible to isolate that to very decent levels...
As for budget..I do a lot of building , I own this very large building and have logged many years doing extensive and varied rehab on it. i also ran a lot of small crews doing various levels of construction to earn a living during periods of my life.
Great! So you have the tools, the manpower, and the expertise to do this right, and you know building materials and construction techniques well, too. That's a really good start.
Estimates on this will never be realized..I tend to look for the right solution for my needs by discussion and then filtering effectiveness of various schemes and weighing that against what i know the materials run per square foot.
I can add a bit of data to that, which should help. Clients who have built studios I designed tell me that their actual construction costs are in the range of maybe US$ 80 to 180 per square foot for a ground-up build, and about a quarter to half that for modifying an existing building. Very broad range, yes, but there's a very broad range of what people need for their studios. That seems to hold true across most of the USA. In your case, probably lower since you are in the industry, and you know where to find less expensive materials, and how to control labor costs. So maybe knock 10% off that.
This project is going to be lumber, drywall, screws and adhesive, hoping mainly for tips on decoupling walls and decoupling walls from floors and from each other via floor..in a sense..the design for me on this one comes down to a few engineering schemes for wht i know is about to happen...i hope that makes sense?
That makes perfect sense, and now I can get back to the point I made above, about your approach to isolation, with separate plans for the ceiling, the walls, the floor, the doors, windows, etc. Unfortunately, isolation doesn't work like that. Isolation is a system, not a bunch of parts. It is the way all the parts work together that matters, not so much the individual parts. So building a ceiling one way, a wall another way, then thinking about the floor at another time, then maybe the doors.... You probably won't like what I'm going to say here, but that approach is doomed to failure. You can't successfully isolate a room by looking at it as individual parts to be isolated separately, such as walls, ceilings, doors, etc. You can only successfully isolate it, by looking at it as a whole: a complete resonant system. Because that's exactly what it is!
The walls, floor, windows, ceiling and etc. all work together to create the overall isolation, and the total isolation can never be better than the weakest part. That's a key rule that should guide you here, and it is very logical. Let's say somebody built a room out in the open, and all the walls isolate to 50 dB, the doors are good for 45 dB, the windows are good for 60 dB, and the ceiling is good for 30 dB. What's the total isolation? About 30 dB. The weakest part sets the limit. In this hypothetical case, the ceiling is the weakest, at 30 dB, so all of the time, money and effort spent on building the other stuff to a higher level, is totally wasted.... unless the ceiling is modified for 50 dB, then it all makes sense again!
So how does that work in practice? As I mentioned it's a resonant system, and THAT is what creates the isolation: It's arises as a product of the arrangement of the parts, which TOGETHER form a resonant system. With such a system, the total isolation is far, far higher than the isolation produced by the individual parts, or even the sum of the individual parts. Resonance is a very powerful tool in acoustics. At the resonant frequency of the system, it does not isolate at all, and in fact it can amplify the sound, but at all frequencies greater than twice the resonant frequency, it isolates very well. So the key is to "tune" the system such that the resonance is no higher than half of the lowest frequency that you need to isolate. It's that simple. If you tune it wrong, or of you build it wrong so that it does not resonate, then you get lousy isolation. If you build it right, then you get good isolation.
So how do you tune it? Also simple: you build it as a "fully-decoupled two-leaf MSM" structure. Also sometimes referred to as a "room within a room", or even "box in a box". In other words, you need to have two "shells" or two "leaves", and they must not be connected to each other. You have an "outer leaf", and an "inner leaf", each of which is a completely self-supporting structure, and the two leaves do not even touch each other. You already have your outer leaf: the building itself. The walls, floor, ceiling, doors, windows, etc. form a complete "envelope" or "shell" that surrounds the empty air inside. That's your outer leaf. Then all you need to do is to build your "inner leaf" within that shell, consisting of four walls and a ceiling, with the associated doors and windows. That will be your inner leaf. As you mentioned, it will be stud-framed walls with drywall on only ONE side of the frame (not both), but the part you got wrong was the ceiling: your inner-leaf ceiling cannot be attached to the existing outer-leaf roof, and it cannot be built as separate panels between the outer-leaf trusses either. Ideally, the inner-leaf ceiling rests only on the inner-leaf walls, or at best it is a structure that is hung from the outer-leaf roof on suitable resilient mounts that are tuned to the right resonant frequency (the same as the one of the walls), and only has hard connections to the inner-leaf walls.
That's the basic outline: you have an outer box (the building), and you need to build an inner "box". The inner box is a complete, consistent, coherent, shell that stand on it's own, and it does not touch the outer leaf at any point: no hard connections. Both shells are sealed airtight.
How do you tune it? By adjusting the mass of each leaf, and the air gap between them, and the insulation that fills that air gap. There are equations and calculators for figuring that out. They will help you figure out the set of building materials that you need to build up the mass, and the size of the gap between the leaves, and the insulation, that is right to get the resonant frequency you need, and the isolation that you need. And to clarify one more time: it's not so much the individual parts of the wall or ceiling that do the isolating, but rather the system as a whole. The individual parts play a role, for sure, but it's the system that gets you the isolation. Tune it wrong, and it will isolate poorly. Tune it right, and it isolates well.
That's the way to do it: design it and built it as a properly tuned system. Then you can get very good isolation.
..and perhaps a second layer of drywall with a green glue type product...though..i do have to suss out the cost of green glue vs benefit..
Simple rule of thumb; Green Glue will get you very roughly as much benefit as an extra layer of 5/8" drywall. So if the installed cost of the drywall is higher than that of the GG, then go with the drywall. But if it isn't, or if drywall would add too much extra weight, or take too long to do, then go with the GG. It is simple, fast, and effective.
I do have some hand drawn elevations and plans of the space which i will upload in a post here..I'll also send some photos..
Cool! Looking forward to seeing those.
Both of you gentlemen who responded so far have convinced me to stay with flat ceilings..
And Andre too, over at GearSlutz! Listen to him: he's one of the most highly respected acousticians around. Very smart guy.
- Stuart -
