John Sayers' Recording Studio Design Forum

Stuart, what happens if I go with the ceiling as is?????? The rails are aluminum and they are attached to the wood studs.

They can sustain the weight of the cloud with the ceiling system I got.

If the resilient channels are on the wall and they are decoupled I do not see, according to the air spring air explanation, how the sound would render my ceiling
solution unworkable (please explain it to me like you did previously).

There are many studios in this forum that have used resilient channels on their ceilings, hangers sound like a WAY to complicated process
both in the space required and the time the process will consume (not to mention what it would cost).

I might be miss understanding you. Do you mean hangers on the walls?

Or something like this http://www.soundisolationcompany.com/sound-solutions/accessories/privacy-wire-tie-isolation-hangars/

I think I mixed up bass hangers with the ones you referred to ( I am obviously a newbie at this).


I have included a link that might be relevant for other people getting confused with how sound travel.
If the content of the article is inaccurate please let me know.
http://forum.ecoustics.com/bbs/messages/34579/128699.html


The EPMD rubber on the rails has to do something in terms of sound isolation and if they don't, the walls with resilient channels together
with bass traps at the corners and eventual bass hangers by the motif construction has to do something in terms of limiting the sound.

I mean, as much banging noise my neighbors have had to endure they would probably prefer to hear a kick drum for 250 hours at 6000 decibels
if you know what I am saying. (excuse the frustration, feels good to blow a little steem)

Sincerely,

Useg Diaz-Granados



Would I get any reductions in terms of sound isolation with my current solution (I know you can't give me an exact number, just give me a
ball park figure........PLEASE)??????

Can you make an aquarium by putting glass only on the front and back? Obviously, you cannot. The water will spill out through the open sides. Can you isolate a room by treating only the walls? No, for the same reason: the sound will spill out through the ceiling. If you do not isolate the ceiling to the same level as the walls, then the sound will simply ignore the walls and take the easy path out through the ceiling. If you have your walls isolated with an air gap of 4" (studs plus resilient channel) but then you try to isolate your ceiling with only 1/2" air gap (just resilient channel, no studs) then you do not have the same amount of isolation: your ceiling will be much "weaker" acoustically.

The mathematical equation that defines how much isolation you get depends on two main variables; the mass and the air gap. If you reduce either the mass or the air gap, then you reduce the isolation.

Therefore, to get the same isolation in the ceiling as you will get on the walls, you also have to have a 4" air gap between your new ceiling and your existing ceiling. This is simple physics. The mathematics is not complex. If you only have a 1/2" air gap up there (instead of 4"), then you will need about eight times as much mass to compensate. So you would need sixteen layers of drywall on your ceiling!

That's why I say that you don't have much choice: you need a 4" air gap between your new ceiling and your existing ceiling. You can get that gap by putting "studs" and resilient channel across the ceiling, just like you did with the walls (except that studs on the ceiling are actually called "joists"), or you can do it with another, easier method, such as isolation hangers.

Here are some examples of what I'm talking about with isolation hangers:

http://www.kineticsnoise.com/arch/muta.aspx
http://www.cmsantivibration.co.uk/produ ... ionhangers
http://www.mason-uk.co.uk/pages/index.h ... ngers.html
http://www.acousticalsolutions.com/isol ... on-hangers
http://www.kineticsnoise.com/arch/ceilings.aspx
http://www.veco-ny.com/images/P-16.pdf
http://www.vibracoustics.com/osb/showit ... ategory=14

That's what you should do on the ceiling. If you don't have the same size air gap and the same amount of mass (drywall) on the ceiling and on the walls, then you don't get any isolation: all your work on the walls is wasted.

---

Yes there are, but they do it from JOISTS! They first have the joists across the top of the room, then they attach the RC to the bottom of the joists, so that they have at least 4" of space between the new ceiling and whatever is above the joists.

The important thing is having that 4" air gap, and also having the decoupling.

It's about the same amount of work, I would say. But you can go with joists and resilient channel if you want. What you CANNOT do is to just attach the resilient channel directly to the concrete ceiling above you: that will not work.

Actually, that is not doing anything for you, since you have screws that connect the rail to the studs directly, bypassing the rubber! So that rubber is doing nothing at all for you: vibrations will take the easy path, through the screws.

I also don't understand the purpose of the rails! I though you were going to put resilient channel on the studs? What are those rails for?

Fully coupled 3-leaf wall? Very rough guess: maybe 35 to 40 dB of transmission loss (if it is very well built). But if you build it CORRECTLY, as a proper MSM system with decoupling, 4" air gaps, only two leaves and good seals, then you could get easily 60 to 65 dB, perhaps more. That is a HUGE difference. 60 decibels is one thousand times better than 30 decibels (the decibels scale is logarithmic, not linear).

30 dB of isolation is not good (about what you get in a normal house wall with thin drywall on 2x4 studs.) 40 db isn't that great either. 50 db means that you cannot hear people speaking any more, but you can still hear music. 60 db means that the music is very faint: you can only just hear it. 70 db means that even very loud music is almost inaudible. At 80 dB of isolation, things have to be REALLY loud before you can hear even a little bit through the wall. Over 90 dB is pretty much total silence (except maybe for exploding bombs and crashing trains).

- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.

Stuart, you are an angel!

Thank you (once again) for the simple and consise explanations.

The rails are a part of a free bearing ceiling system that I have not yet constructed.

The Beams connect to rails that are joisted together with steel to steel screws, they are also used to contain 70 mm of isolation and to screw the drywall into.

Since 4 inches is 10.2 cm, the system that I purchased would be have to lowered 3.2 cm in order to have the 10.2 cm gap that you suggested which means
that I have to make some adjustments to my air duct because it is "placed to high".

The problem is like you so eloquently illustrated that the rails are screwed into the studs.

My question this time Stuart is is there a way for me to decouple the rails?

Sincerely,

Useg Diaz-Granados

Salud! I hope that's Chilean wine in the glass, or you get no more help from me!!!!

Seriously, regarding decoupling the rails: I wouldn't use rails at all. I don't think they can be decoupled easily!

To be very honest, what I would do in your situation is to return the rails to the store, and swap them for some more 2x4 wood. Put those across the room, attached to your wall studs (bolts maybe), screw resilient channel to the bottom of the joists, and attach your ceiling to that.

This will fix your isolation issue, but is doesn't solve the cloud problem. So I'd make your cloud from light weight materials, then there won't even be any problem! Or you could put in a couple of extra strips of resilient channel (and carefully note the exact positions, so you can find them again once the drywall is up!), so that you can spread the weight of your cloud around, across several strips of resilient channel. Lets say that your cloud ends up weighing 40 kg (for example). If you hang that from 8 wires, each wire only takes 5 kg. If that is spread across four channels (two wires on each channel), then each channel is only taking an extra 10 kg. Hardly anything, compared to the weight of the drywall that it is already supporting. Of course, you still have to do the calculations to make sure you are not overloading anything!

That would be my approach. Maybe someone else has alternative ideas.



- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.

October 1, 2010 I asked:

"where are your plans and could you elaborate on this building, the dimensions, what it is constructed of, how it is constructed."

Which you never answered...so I made some assumptions, if they were incorrect it is due to incorrect or in complete information.

I have a chip on my shoulder as well...it has a bullseye that often people aim for...I'll trade mine for yours if you have the spirit to wear it proudly

Good luck,

_________________
Brien Holcombe
_____________________________________________
Sound: You can't stop it, you can only try to contain it.

I think it would be impossible for me to return the rails so I would have to take the loss. I will look into decoupling the rails.

Brien, fair enough. You meant Oct 2010, (good thing you changed your original post when I pointed this out) make me feel better that I am not the only one making misstakes
(think the chip fell of my shoulder).

Sincerely,

Useg Diaz-Granados

I found a decoupling device that I hope will do the trick.
http://www.acousticalsurfaces.com/rsic_clips/risc_dco4.htm?d=46

Sincerely,

Useg Diaz-Granados

Those may be a good choice, also look at mason industries and kinetics noise for option on commercial isolating products which may work as well or better.

_________________
Glenn

Agree with Glenn. Those two were at the top of the list I posted earlier (although that was a list for isolation hangers).

- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.

Decoupling is not what you want...since what you will establish will be an assembly with multiple air spaces, small at that.

Either mass against the existing wall or remove the interior and work out from there. These efforts to make this work....in hindsight, are going to cost you in both areas.

Nothing against what the mods are saying, all I am saying is that you are too deep in this and the points that should have been addressed or submitted by the OP were not, and this brings us to where we are.

It works like an inside out wall as it is...mass directly to the walls. But there is a lot of things that have not been addressed.

The strong points in this build is that we have some valid assumption that the floor and the ceiling are concrete.

The weak points will be the wall assemblies and anything you do to alter them....plus windows and doors:)

_________________
Brien Holcombe
_____________________________________________
Sound: You can't stop it, you can only try to contain it.

Whoa! You mean the walls are not concrete too? Not sure why I assumed they were!

If the walls are ordinary stud walls with drywall on each side, then you have another problem, just like Brien says.

Please can you confirm if this is the case? Are your walls ordinary 2x4 stud framing with drywall on each side?

- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.

The walls are drywall not concrete.

The stud construction is made out of 145/45 mm (145mm cavity=5.708661417329 inches) wood which is connected to the drywall structure that was already there (the original walls/the drywall you see connected to the studs).

The studs lay on 145/45mm wood pieces that are "flat on the floor" connected to the walls with steel brackets.


The floor and the ceiling are made out of solid concrete.

Some of the studs touch the concrete slabs on the ceiling but they are not connected or screwed in any way to it (the ceiling that is).

Everything have been carefully caulked.

As I stated in the beginning of this project having an accurate room (mixes that translate accurately) is my main objective.

Not being an expert, it makes sense for me to buy the decoupling devices just like the MODS suggested, along with the resilient channels for the walls, because of the fact that tearing down the original drywall (which happens to be connected to my neighbors apartment) is not an option.

I presume that decoupling the wall and the ceiling (along with caulking the place right) is a good thing.

If it is not; I would like to have it explained in the way that Stuart and Glenn (and some of the others) have been able to explain things.

Another option would be to get the overly priced (because of the shipping expenses to Sweden) Green Glue (for the ceiling only) along with the decoupling devices that will allow me to install the ceiling system I already purchased. But this option seems useless if the ceiling already is decoupled.

Brien, could you (or anyone else) explain why "the series of pockets of air" would be a bad thing??????(......air pockets, that take away from the mass required to isolate the sound/reduces the low end of the assembly due to multiple hard air spaces)

If anyone have something to add because of what Brien has presented, or have any additional information with regards to the best way to sound isolate the room, I am all ears

Sincerely yours,

Useg Diaz-Granados
......

I think the concern Brien is raising is multiple leafs can reduce isolation so the ideal is a double leaf Mass-air-mass but you have restrictions on removing the existing drywall etc, you will have to live with the possibility that you have less isolation than you might like. So decoupling as much as possible, using insulation to dampen the cavities, and increasing your mass on the inside will get you as far as your situation allows.

_________________
Glenn

Thank you for the straight to the point response Glenn. I will do my best, follow your advice and move along with the project.

Sincerely,

Useg

Resilient channel is what you are looking for at this stage of the build. Going back and undoing what you already have constructed and caulked in may be more than you are 1. willing to do and 2. may not be as structurally sound once moved.

But which ever is the lessor of the two evils from your perspective/time. Yes the multiple air spaces are a concern since this does have data supporting that the stc will be reduced and the transmission loss is reduced at the lower frequency but the high frequency end of the spectrum is actually increased...but the low end is the most important for isolation of sound.

_________________
Brien Holcombe
_____________________________________________
Sound: You can't stop it, you can only try to contain it.