2 Soundproofing Options for a Ceiling...Which one is better?

[treatments]

Hello,

I have already posted and received great feedback concerning this subject, but I have come up with a second option, and would like to get some feedback about which one would be better.


I would like to improve isolation between floors in my building. The control room is located on the second floor, and the live room is directly below it on the ground floor. I need to try and minimize impact noises from above, as well as transmission from the live room to the control room. Building construction is brick/cider block. Ground floor is concrete. I-beams and 2x10’s support the second floor, which is made up of 6” wide planks, a layer of plywood, and cheap thin tiles.


Soundproofing ceiling in live room Option#1

In option#1, I tear out the existing ceiling, preserving as much as the old drywall as possible, in order to use it in between the floor joists along with some insulation. I would then build a small frame around the I-beams, attach clips/hat channel to the new framing, as well as to all the joists, and suspend 2x 5/8” drywall.


Soundproofing ceiling in live room Option#2

In option#2, I leave the existing ceiling. The ceiling height in the live room is 10’. There are 3 I-beams that drop down about 6” every 11’, creating 3 separate cavities. In this option, cellulose insulation is blown-in the entire existing ceiling. Then, a new steel joist system is attached to the sides of the I-beams. Insulation is placed between the steel joists, filling the 3 cavities, and 2x 5/8” drywall is then attached to the new joist system.

This option does create a 3-leaf effect, but the second air space (between the existing ceiling and the new one) will end up being approximately 8”.

Also, to limit the leaf effect in the assembly, I would make lots of holes for the cellulose and cover them with a screen so air (and some low frequencies) can pass through the middle leaf. It would behave like an acoustic panel designed to absorb bass.



Which option do you think is better?

Thanks,

Gilles

[Soundman2020]

I have already posted and received great feedback concerning this subject, ...

It's better to keep all your questions about your build together in one single thread, where possible, so that you (and we!) always know where to find the relevant information. At some point in the future, you might need to come back to revisit this question, or the other one, and not be able to find it easily if you have several threads running...

Anyway, ...:

I would like to improve isolation between floors in my building.

How much isolation do you need (decibels), and at what frequencies? That's the key to successfully designing and building any isolation system. Since 2-leaf and 3-leaf systems are tuned, it is important to know what frequency you need to tune yours to, such that it will provide the right amount of isolation at the right frequencies.

I-beams and 2x10’s support the second floor, which is made up of 6” wide planks, a layer of plywood, and cheap thin tiles.

A diagram or photo would make it easier to see what you are dealing with, and to help you find the best solution.

In option#1, I tear out the existing ceiling, preserving as much as the old drywall as possible, in order to use it in between the floor joists along with some insulation. I would then build a small frame around the I-beams, attach clips/hat channel to the new framing, as well as to all the joists, and suspend 2x 5/8” drywall.

That would certainly work, and that's how a lot of people do it. However, in your case you have total access to the floor upstairs, so it would be much easier, and much faster, to just add the extra mass from above: Take off the tiles, put down another layer (or two) of thick plywood, then put your final flooring on top of that: Maybe tiles again, or laminate flooring, for example.

Soundproofing ceiling in live room Option#2

In option#2, I leave the existing ceiling. The ceiling height in the live room is 10’. There are 3 I-beams that drop down about 6” every 11’, creating 3 separate cavities. In this option, cellulose insulation is blown-in the entire existing ceiling. Then, a new steel joist system is attached to the sides of the I-beams. Insulation is placed between the steel joists, filling the 3 cavities, and 2x 5/8” drywall is then attached to the new joist system.

That sounds expensive and complex, although it could work if done right. Also, I'm not a big fan of blown-in cellulose, since it doesn't always settle evenly: you can end up with both voids and clumps...

This option does create a 3-leaf effect, but the second air space (between the existing ceiling and the new one) will end up being approximately 8”.

8" isn't all that much, for a 3-leaf system. If you can figure out the mass of each (surface density) then I can calculate the resonant frequencies for you.

Also, to limit the leaf effect in the assembly, I would make lots of holes for the cellulose and cover them with a screen so air (and some low frequencies) can pass through the middle leaf. It would behave like an acoustic panel designed to absorb bass

Actually, it would act like a perforated panel resonator, tuned to a frequency defined by the hole size and separation, and therefor percentage coverage. So the upper half or your 3-leaf system would be absorbing a range of frequencies centered around the tuned center frequency, which might or might not be a good thing. But it certainly does drastically change what the ceiling is doing: it is no longer a simple 3-leaf system, but rather a perforated panel resonator trapped between two massive surfaces: I have no idea how that would perform, and I'm not aware of any software that would be able to predict the performance accurately...

- Stuart -

[treatments]

Hey Stuart,

Thanks for the heads-up on re-posting stuff.

A diagram or photo would make it easier to see what you are dealing with, and to help you find the best solution.

I'm working on a diagram of the floor construction, and I'll post some photos as well.

That would certainly work, and that's how a lot of people do it. However, in your case you have total access to the floor upstairs, so it would be much easier, and much faster, to just add the extra mass from above: Take off the tiles, put down another layer (or two) of thick plywood, then put your final flooring on top of that: Maybe tiles again, or laminate flooring, for example.

I forgot to mention that the height of the ceiling in the control room on the second floor is only 8' and is simply a rectangular room at the moment measuring 19'x36'. I have thought about adding a couple layers of plywood, but was afraid of loosing too much height. Would you still recommend adding the mass from above?

Gilles

[treatments]

How much isolation do you need (decibels), and at what frequencies? That's the key to successfully designing and building any isolation system. Since 2-leaf and 3-leaf systems are tuned, it is important to know what frequency you need to tune yours to, such that it will provide the right amount of isolation at the right frequencies.

I need to try to reduce the amount of sound transmission coming through the floor/ceiling, mostly low frequencies, from the bands playing downstairs. Currently there is only about 25 decibels of isolation from the live room to the control room.

Also, I need to reduce the amount of footfall noise, as well as playback coming from upstairs in the control room. Currently there is only about 32 decibels of isolation from the control room above during playback.

When I'm recording something quiet like a vocal, piano, or acoustic guitar in the live room (ground floor), the microphone will sometimes react to the footfall noise coming from the control room (second floor), thus creating a feedback loop.

I like the idea of adding mass from above, but that will take away a good 3” from my already low ceiling height of 8’.

[treatments]

Hello Everyone,

Taking in consideration that my ceiling height in the control room is only 8' on the second floor, and you had the option of soundproofing from above (build on the floor), or below (tear out ceiling and rebuild), which one would you choose?

This is what I came up with for the floor option:

-seal floor with ployethelene
-layer of 2" Roxul RHT 40
-layer of 5/8" OSB tongue and groove
-layer of 5/8" plywood tongue and groove
-layer of finishes flooring (plywood, or floating floor)

This is my ceiling option:

-tear out existing ceiling
-stuff with insulation (either the Roxul RHT 40, or Roxul Safe n Sound)
-install clips and hat channel
-2x staggered 5/8" drywall (maybe green glue in between)

Thanks!

[stevev]

hey Gilles, working on the floor is the easiest option by far as you're not trying to remove and reinstall material from above your head. Ceilings are a hard part of any build purely due to the amount of lifting involved.

-seal floor with ployethelene
-layer of 2" Roxul RHT 40
-layer of 5/8" OSB tongue and groove
-layer of 5/8" plywood tongue and groove
-layer of finishes flooring (plywood, or floating floor)

That sounds good except for the Roxul. If that is a compressible insulation (which I believe it is) it'll be no good to put over the existing floor. The floor will be physically bouncy and you won't have any way of screwing down your tounge and groove or ply.

You may also be able to use GG between these layers, but double check that with them.



This is my ceiling option:

-tear out existing ceiling
-stuff with insulation (either the Roxul RHT 40, or Roxul Safe n Sound)
-install clips and hat channel
-2x staggered 5/8" drywall (maybe green glue in between)

That's the way to do a ceiling Watch out for 'stuffing' the insulation in. You don't want to compress it, it justs wants to sit there. I would highly recommend GG between your layers of plaster board as I've used it myself and it does what it says (if applied correctly and in the required amount) . Make sure you get the right amount of isolation clips per square meter/foot so that they load properly.

I guess you could do the floor to start with, and if that doesn't get you the isolation you require then consider doing the ceiling below as well. Oh, and before you do any of this, make sure the floor/ceiling structure can take all the additional weight you might be adding

cheers,

steve