Need help fixing a 3 leaf and isolation problem, please.

SoundBoy · **Posted:** Thu May 24, 2012 4:56 pm

Hey Stuart,

Quote:

Is there any reason why you don't want to do the ceiling in the normal, conventional, economic, and simple way? Why do you need to go to all that trouble and expense?

Im not sure what you mean. I thought thats what I was doing? Assides from the bulkhead for the lighting what am I doing with the ceiling that isnt the normal way?

Quote:

On the side of the CR there is an issue: the window to the outside! There is only ONE piece of glass there. Only an outer leaf, no inner leaf.

Did you have a look at how I added your suggestion to fix the control room wall on the left with extra glass?

Appreciate the response.

G

Soundman2020 · **Posted:** Fri May 25, 2012 7:07 am

Quote:

Im not sure what you mean. I thought thats what I was doing? Assides from the bulkhead for the lighting what am I doing with the ceiling that isnt the normal way?

The normal way is just to put joists across the tops of the new inner-leaf walls, and hang your drywall from those. Simple, cheap, and very effective. No suspension system required.

I mentioned that in my first post: "the ceiling joists for that ceiling can ONLY rest on the new stud walls, and cannot touch anything else". But then you went ahead with the suspended ceiling instead, so I thought you must have a reason for going that way, instead of the normal way.

This would cost a lot less than the proposed suspended ceiling, be much easier to build, and the isolation would be better since there would be no contact at all between inner and outer leaf.

Quote:

I then plan to build a bulk head right around the perimeter of the room about 50mm below the ceiling. The bulk head will house the lights, both recessed LED strips and down lighters. Not only will this look pretty nice but it also solves the problem of the lights creating holes in the actual ceiling. Do you foresee any problems with this?

While that would work aesthetically, the problem I see is acoustically: Corners are very precious real estate for bass trapping. If you run that around the entire perimeter, you eliminate eight of your twelve possible corners, leaving you with only the floor-wall corners for bass trapping (and maybe half of the verticals). That probably won't be enough, and also would make it hard to deal with modal issues that involve the ceiling. Plus, it might be hard to accomplish! Floor-wall corners are normally the last ones to get treatment, after all other options have proven insufficient.

I'd suggest using your cloud for lighting. You can put lights both above and below, as many as you want, facing any way you want, for some neat effects. That would leave the corners available for treatment.

Quote:

One last thing, in my last revision of the sketchup model youl see I angled the glass between the LR and CR. After some research I have decided not to do this and both glass panels will be mounted straight. This will also create a 250mm gap between the two which should be pretty decent for isolation. The glass I have is 6mm laminated.

Theoretically, that window should have a resonant frequency of about 40 Hz, should start isolating at about 62 Hz, and should isolate well above 93 Hz. Isolation should be around 45 dB.

- Stuart -

SoundBoy · **Posted:** Fri May 25, 2012 7:53 am

Hey Stuart,

Oh ok I see what you mean. Well the main reason for suspending the ceiling is simple. The tracks and studs used in the wall are the steel kind. I am not 100% sure and would have to do some research but I don't think this kind of wall is meant to be load bearing and I'm not sure if it would take the 30kg/m2 (+- 800kg total) ceiling I plan to build. I could very well be wrong though. If I am then I definitely agree a joist system would be preferable. I will look into it.

Will definitely look into the bulk head issue then, you are right.

I was looking at the walls and I've come across allot of research that is confusing me. Some places say that its better to use alternating thicknesses of board when stacking them together for a leaf, others say use all the same thickness (as you did). I understand the logic in both, alternating thickness = more change for the energy to pass through. Same thickness = more mass for the energy to pass through. If I could for instance use: In the LR - 2x 15mm board + 1x 12mm board for inside leaf and CR - 1x 15mm + 1x 12mm for inside leaf. It would save quite a bit of money. Since the 15mm boards are almost double the price of the 12mm! (budget is the only issue forcing this question)

I think I will do a build diary on the forum when I start the refurb.

Thanks again mate

G

SoundBoy · **Posted:** Fri May 25, 2012 7:57 am

Do you think I should look into thicker glass? would it help raise that 45db isolation?

Soundman2020 · **Posted:** Fri May 25, 2012 10:12 am

There's two types of steel studs. Non load-bearing and load-bearing. Basically, the load-bearing type is just heavier gauge, stronger. So find out what type you have. If it is load-bearing, then you can simplify things by doing the ceiling the traditional way.

The issue with your suspended ceiling is that it is not decoupled. You should really use isolation hangers for that application, or else the building noise will still get into your room, via the metal straps. You'd need one isolation hanger for each strap.

Quote:

I was looking at the walls and I've come across allot of research that is confusing me. Some places say that its better to use alternating thicknesses of board when stacking them together for a leaf, others say use all the same thickness (as you did). I understand the logic in both, alternating thickness = more change for the energy to pass through. Same thickness = more mass for the energy to pass through.

The issue is this: Yes you do get benefits from different layers due to refraction, diffraction, impedance mismatch, different coincidence dip frequencies, etc. But they are minor. And you do get gains from the additional mass: also not much, but a bit more worthwhile. So the mass beats the other things. Then you have the problem of the thin things in the middle: thin things have high resonant frequencies, are flexible, etc. Not good. And even though the wall acts as a unit, the parts also act individually, so that "thin thing" in the middle is not doing nice things, in terms of resonance, flexibility, rigidity, mass, etc. So you have a good wall with a bad "thing" inside. Much better to have a good wall with all good things inside, in my opinion. Overall, it makes more sense to just keep all layers as thick as you can. And if you really do want to put something in the middle, then put Green Glue in there: that really is worthwhile.

Quote:

Since the 15mm boards are almost double the price of the 12mm! (budget is the only issue forcing this question)

Have you looked at other things, beside drywall? MDF, OSB, plywood, fiber-cement board are all alternatives. The fiber-cement is about double the density of the others, so you can make it half as thick. Mass is mass, so go for the cheapest mass. If it isn't drywall, then use whatever is cheapest.

Quote:

Do you think I should look into thicker glass? would it help raise that 45db isolation?

Yep! How much isolation do you want?

The key here is surface density: The surface density of the entire wall should be constant. So figure out the surface density of the rest of your wall (kg/m2), and then look for the type/thickness of glass that matches that, or is a bit more. That's the glass you need. Normal glass is about 3 to 4 times as dense as drywall, so for example if you were going to use 3 layers of 15mm drywall, then you'd need 12mm to 15mm glass to maintain the same surface density.

- Stuart -

Gloseloth56 · **Joined:** Sat May 26, 2012 3:47 pm **Posts:** 2

SoundBoy wrote:

Hey everyone,

I need your help. Ok so after doing some tests on my newly built live room, I am not happy. I was stupid to think I would get a decent result with what I built in the first place so yes I am quite the idiot in this case. But please if you can all be kind enough to look past that I have been so silly I really need help to fix it :oops:

, Ill tare down walls if I have to (the ones I can anyway) So Im looking for anyone who would be kind enough to advise me on how to solve the issue. I'm busy drawing up some detailed sketchup models of the whole thing so anyone who is willing to help me can understand the problem fully. I will post up some illustrations as well.

The basics:

The studio consists of two rooms (live and control) located on the first floor of a office building. The surrounding space is offices. All the walls are a standard drywall (single board-studs-single board, with insulation) no decoupling. The floor is concrete slab. The ceiling is suspended from the slab above. The cavity between the ceiling and slab above is about 1 meter.

What kind of Isolation I am looking for:

The studio will only function at night and on weekends when the surrounding offices are unoccupied. So to be honest I don't care how much noise gets out. I have no neighbors that I will be bothering while I am working. Also so far Ive checked that even with the monitors blasting there isnt much noise past the front door to the lift lobby anyway, so the only offices that are affected are the ones literally right next to me (I will include a floor plan to illustrate). What does matter to me is the noise that gets in. Particularly in the live room. I want the live room as quiet as I can get it. I am happy with the current isolation of the control room since the surrounding environment is pretty quiet already. But when I set my mic gain up to a decent level I am not happy with the isolation of the live room so far.

The dreaded triple leaf:

Before learning how bad this is, I went and built a triple leaf system in between the live and control room. I think?

I was looking into just leaving the rooms as they are and then building a new room inside the live room (room in a room). New walls right round the inside decoupled from the floor and existing walls, supporting a second ceiling which will obviously not touch the existing suspended ceiling above. And double door. But I am scared this will just create a 4 leaf system in between the LR and CR and will also then create a 3 leaf on all the existing walls that are currently just normal dry wall. So I am very hesitant to do this without some advice first.

I could really use your help on this guys, I want to get this place up and running but I need to be pointed in the right direction.

what do you guys think?

G

worth to read about it. thanks for the moderator for the answer

[AND THANKS TO THE MODERATOR FOR REMOVING YOUR SPAM SIGNATURE]

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Need help fixing a 3 leaf and isolation problem, please.

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