I just realized you are posting on the GS forum too?
Occasionally, yes! But not nearly so much as here, for various reasons...
My main question is whether its silly for me to be bothering you or other folks who design spaces specifically dedicated to recording.
Not silly at all! Acoustics is acoustics, and it applies to all rooms, just the same (well.... with some caveats....). The same basic principles work for whatever it is you need to do.
This is a multi-use room that will get lots of use for making music but it has to also be a space for hospitality.
No problem. There's treatment that can be used to get whatever result you want. I also have clients who are churches, for example: not related to recording or studios at all. That's probably closer to what you need than a recording setup.
Right now my biggest question is about what goes in the walls and then a double layer of sheetrock on walls and ceiling with GG.
What I would suggest is that you first define how much isolation you need, in decibels. That's an important starting point for designing your room. Do some tests with a sound level meter and a loud sound source set up in the room, and see how loud that it outside, and at other points in the building, then based on that, you can take a look at your isolation options. It's much better to work from a known starting point towards a known goal, rather than just guessing at different approaches, and hoping the one you chose will help.
I'll be honest with you, and say that after you have done the tests, defined a number, and looked at your options, you probably won't be very happy. Your room is on an upper floor (not the ground floor), which already makes it hard to isolate, you plan to have loud instruments in there, some of which are hard to isolate, and your budget is very tight. So I would suspect that what you need to do, in terms of isolation, wont be achievable. That doesn't mean that the room is going to be a failure! Not at all. It just means that you'll probably need to downgrade your expectations, and live with then consequences of less isolation that you really need.
So, that leads to the question: Is it worth spending a lot of money to get to a situation that isn't what you need? For example, let's say, for argument's sake, that right now you are getting 30 dB of isolation, that you calculate you need 60 dB of isolation to do what you want, but that by spending half your entire budget just in isolation, you can only get to 40 dB, and even if you spent all of it on isolation it would still only be about 45 dB (for example!). Is that worthwhile? That's a call only you can make. Is it worthwhile spending a lot of money for only a small improvement in isolation?
Perhaps it would be better to just live with what you have, and instead spend money on treating the room so it sounds good inside, and looks nice, and is comfortable, even though it doesn't isolate? That's something I can't tell you. I can just give you the numbers and the methods and the materials, but you have to decide if less-than-optimal is still a worthwhile goal.
I think it was your post Stuart about how GG does not decouple in one GS thread.
Ah yes. The "Ham Sandwich" post!
Right. decoupling is not what GG does: it helps to improve isolation, and in a wall that is already decoupled it works really well... less so in a non-decoupled wall. True.
Right now my biggest question is about what goes in the walls and then a double layer of sheetrock on walls and ceiling with GG.
It will help, yes, but it isn't magic. It's not going to give you excellent improvement in isolation. It will do something, for sure, but if you don't decouple, then you are basically limited by a principle of physics called "mass law". It's a very simple equation, actually:
TL = 14.5 log (Ms * 0.205) + 23 dB
Where: M = Surface Mass in kg/m2
If you do the math, you'll see that each time you DOUBLE the mass of a single-leaf barrier, you get an increase of about 6 dB in isolation. Subjectively, you need an increase of 10 dB for you to judge that the level dropped to half of what it was. So, if you have a wall with a total of two layers of drywall on it, and you are getting 30 dB of isolation (for example), then you add another two layers, you will now get 36 dB of isolation. The perceived level will have dropped a bit, but not much. If you then add another FOUR layers of drywall to that wall (in addition to the four you have at this point), your would get another dB (because you doubled the mass again), so now you have 32 dB, and it sounds about half as loud as it was originally. But you had to get a total of eight layers of drywall to get there.
Mass law is not your friend. Single-leaf barriers are subject to mass law.
Now, maybe if you put GG in between all of those new layers of drywall, that might improve things by another 6 dB, (perhaps... I really don't know if that would be the case), so you get a total of 38 dB isolation... which means that, subjectively, the level would now be a bit louder than one quarter of what it was originally. Probably still not enough to be attractive.
To put all of that in perspective: Typical listening levels for mixing are around 80 dB, so if you had 38 dB of isolation, then that would be about 42 dB outside. That's fairly quiet, but not silent. It would need to go down another 10 dB to be really silent for most people.
So, should I still plan to install two layers with GG all the way around even though I have a standard door, the 5x8' window and the two 2x4' windows?
Like I said: measure some real levels with a meter, to see how much isolation you are getting at present, and to also see how quite you need to be (in other words, measure the ambient noise outside when there's no sound at all from you or anyone else). Compare those numbers, to see how much extra you need to get to "silent", then we can help you figure out possible ways to do that, and answer your question more intelligently.
Maybe the answer is "yes"! Maybe what you are proposing is actually going to get you enough extra to be worthwhile. Maybe not. But we'll never know by guessing!
I got a bunch of 2" foam board from a friend at cost.
What type of "foam board"? What is that foam? Is it proper acoustic foam, made be a reputable manufacturer? There's an awful lot of unscrupulous place out there that sell packing foam and upholstery foam, claiming that it is "acoustic", but really it isn't. It can look the same to the untrained eye, but in reality it's not much use at all. So do be careful! Double-check what you have there.
but in the walls I still have 3.5" or so that I can fill with something more? Do I want rockwool or just fiberglass?
Either mineral wool or fiberglass will work fine. If you get mineral wool, then you will need stuff that has a density of around 50 kg/m3. If you get fiberglass, then it needs to be around 30 kg/m3.
Yes, adding insulation inside the wall is a very useful thing, and it will help. Insulation by itself is very lousy at isolating, but when used as part of a system, it has a really good effect. So yes, doing that will help... but once again, is it enough? Especially considering that your ceiling is not isolated, is it worth isolating the walls? Sound will just take the easy path out of the room, so if you isolate the walls very well but do nothing to the ceiling, then you still don't have much isolation! Isolation is only as good as the weakest link.
I know this room will not be near ideal for your standards.
It doesn't have to meet MY standards! It has to meet YOUR standards...
I can help you determine what those standards are, and you can then decide if it will meet them or not, and we can figure out together what you would need to do to meet them. But I'm not going to impose my standards on your place! You set the standards, and I'll help you get there...
I've made lots of music in odd spaces. This room will be a major step up for me.
- Stuart -
