John Sayers' Recording Studio Design Forum

Not a joke at all! Acoustic hangers are frequently used in studios, and work very well. You might want to use the "search" feature of the forum to find out what they are...


- Stuart -

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

Thank you...now this next question I have also sent to the Green Glue folk - but I wonder if anyone here has a POV please ...
Green GLue is SUPER expensive here in Australia - about 3x the price it is in the US, so I have bought just 2 cases, which according to the GG folk should do 12 sheets.

My room within a room build has 3 layers in the 'beefing up' and 3 layers in the inner room.
Each layer will have 8-10 sheets (not all walls are the same - and inner room is smaller etc!) which means that if I follow GG's guidelines I can basically do GG between one entire layer of sheets, and then have a bit extra.

I'm assuming that the best layer to use the GG on would be the inner sheets of the inner room (call them layer one and layer two) and then possibly use the extra between the sheets in betweeen the joists in the outer room ceiling. (Noise transmission UP through the floor of the living room above is the biggest problem....and yes I have understood that noise travels everywhere....!)

Would you experts agree - or suggest something different?
And have any of you played with using LESS GG, but in more layers?

For example I could use 1 and 1/3 tubes of GG (2/3 of the rec amount), between layer one and two, and again between layer 2 and 3, of the inner room.

Thanks as ever....

P

And now I'm onto these - there's lots of good info in the forum - but I have one question - I understand that to minimise noise I need the x sectional area of the duct that comes INTO the room (for the AIR IN) to be double that of the duct as it enters/passes through the silencer....

But what of the duct that takes air FROM the room - the AIR OUT - should this be the same - but in reverse...remembering that we are much more concerned about air-movement noise at the IN end of this duct? Or should it just be 6" throughout?

Thank you

P

Same principle going in and out: You want slow air movement in the parts that are inside the studio, both entry and exit. But once it gets through the silencer on the way out, it doesn't matter so much, so the section can be smaller. Also, the transitions into and out of the room should be smooth, not sudden. In other words, don't go directly from a 6" duct to a 14" register: use something to gradually widen it out over a distance of many inches (sort of like a funnel shape).

- Stuart -

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

Thank you....I saw those 'cone' shapes in some people's pics.
Are you hand-making them...or is there an off the shelf solution to a cone that starts 6" at one end and is 8" (or more) at the other?
P

My room is only 10 cubic metres...so if I go for 10x air replacement an hour, I need a fan/setup that does 100l per hour...which seems well within the spec of a 4" inline centrifugal fan...which would mean a 6" register/ hole in the studio wall for sound to escape through...rather than a 6" duct/8" hole in the studio wall. I can see most people on this site are going 6" plus - but as my little room is so small, is there any reason not to go with the 4" set up?

And I know this might seem daft - but am I right to understand people are using inline fans on BOTH the air in and the air out ducts?

In terms of design/location of the silencers - I have two options.
1 is to place the silencers in a void between my inner room and my outer room (this is a room within a room setup)...though if I go with this setup I will still have the fan(s) outside the outer leaf
2. Is to run the duct straight through the inner and outer leaf into the next door room and have the silencers and fans in a heavily boxed area on the wall in that room.

1 intuitively makes more sense..but I guess the advantage of 2 is that if sound leaks...I can just keep building up the box containing the silencers.

Can anyone please help on this?

THank you

One more odd question - my local green glue folk have suggested I use a strip of http://www.greengluecompany.com/product ... e?p_ins=86
under my inner leaf framework where it touches the concrete slab rather than just setting the timber onto the concrete.
Does anyone have a POV on this - I know that generally on this forum it is NOT recommended that novices like myself 'float' the inner room/its floor off the concrete as getting the maths wrong can mean doing more harm than good with any neoprene etc...but this green glue product is not a compressible rubber....that said, on the green glue site (link above) the application that's suggested is not a timber/concrete one!
All the best
P

I think your local Green Glue folk don't read their own literature! What the Green Glue COMPANY says about their product, is this:

"One of the biggest noise complaints is the sound of footsteps and squeaky floors. The squeaking that’s driving you crazy occurs naturally when floors settle, and joists rub together with subflooring. There’s an easy solution: Green Glue Noiseproofing Joist Tape. The tape creates an airtight seal and dampens foot traffic, so that annoying squeaking becomes a thing of the past."

So unless you are concerned that your concrete floor might squeak when the wall walks on it (:!: ), I'd say that you don't need that stuff, nor would it be useful. It does not claim to decoupled walls from floors, and is not designed or marketed for that purpose, so it seem to me your local GG folk are being more than just a bit overzealous in trying to sell you stuff that you do not need, and will not work for what they are suggesting.

A much better idea would be to buy some acoustic caulk (Green Glue or any other manufacturer) and lay three beads of that on the concrete floor, down the full length of where the sole plate will go, then put the sole plate down on top of that, and nail/screw it in place. One bead goes done the center line of the plate, and the other two about an inch to each side. That will help to give you a good seal under the sole plate, which is what you really need. Then lay another bead of the same acoustic caulk under the edge of each layer of drywall, as you hang it. Rest the drywall on a thin shim while you nail it in place, then take the shim out, but in backer rod, then caulk.

Now, if your concrete is very uneven, and you don't think that you can get a good seal under it just with caulk, then you could use a strip of soft rubber under the sole plate, in order to ensure that you get a perfect seal. But don't expect that the rubber will float the wall: it wont, because you still have to nail / screw / bolt the sole plate through it, into the floor.

And it looks like you'll have to watch out for the advise you get from the folks who want to sell you that stuff! Double check on anything else they might try to sell you...

- Stuart -

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

Thank you Stuart - that makes much more sense!

May I ask a few more important questions that are still bothering me....

1. DUCT SIZE: My room is 9-10 cubic metres...so if I go for 10x air replacement an hour, I need a fan/setup that does 100l per hour...which seems well within the spec of a 4" inline centrifugal fan (160-200l per hour)...which would mean a 6" register/ hole in the studio wall for sound to escape through...rather than an 8" hole (if I went for 6" duct) in the studio wall. I can see most people on this site are going 6" duct or bigger - but as my little room is so small, is there any reason not to go with the 4" set up - the fan still doesn't have to run full speed?

2. SILENCER PLACEMENT: In terms of design/location of the silencers - I have two options.
a) is to place the silencers in a void between my inner room and my outer room (this is a room within a room setup)...NB if I go with this setup I will still have the fan(s) outside the outer leaf
b). Is to run the duct straight through the inner and outer leaf into the next door room and have the silencers and fans in a heavily boxed area on the wall in that room.
a) intuitively makes more sense as my silencers are INSIDE the outer leaf so I'm not ducting sound straight to the outside of my room-in-room setup..but I guess the advantage of b) is that if sound leaks...I can just keep building up the box containing the silencers. (And you have said before to make the silencers accessible, and b) would be more accessible) What do you think?

3. I have now found amongst the images on this site, what looks like a rubber tube used to separate/decouple two pieces of conduit carrying electrical cables. On the assumption that this same model is applied to the air ducts . are you 'making' that rubber tube or does someone sell rubber tube in 4" diameters? And is it a special kind of rubber? And how does one insulate this rubber - it's pretty thin!

4. And I know this might seem daft - but am I right to understand people are using inline fans on BOTH the air in and the air out ducts?

Thank you

P

4" duct has a cross sectional area of about 49.7 square inches. For 6" duct, it is about 111.8 square inches. So to get the same amount of air through the 4" duct, the air velocity needs to be about than 225% higher. Air noise is proportional to the square of the air speed, so you'd be getting a LOT more noise inside that small duct. Maybe that's a good reason?

You might be able to do that, if the gap between the leaves is big enough.

Not a good idea, unless you can decouple the duct in the middle.

If the silencers are located right next to the doors, inside the walls, then they could be accessible. In other words, the side of the silencer would be visible between the inner door jamb and outer door jamb. Once again, that assumes that the air gap is big enough.

Talk to your HVAC supplier: he probably has options for isolating duct: But if you use flex duct, then it doesn't need much isolating. You can insulate the joint by wrapping it with a thick layer of fiberglass or mineral wool.

Yup, that's the best way to do it, especially if the runs are long. The problem then, of course, is balancing the air flow, but that's what dampers are for...


- Stuart -

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

Hi and thank you to everyone who has helped me. The build is well past half way and I couldn't have done it without you.
The outer leaf has been bulked.
And the inner room frame is almost complete.

But I have a question re. the eletrics that I would really appreciate help with (before Tuesday!!! if you possibly can).

I have two places where power comes in to my inner room - one for wall sockets etc (which will all be proud of the wall on the inner leaf), and one where I'm installing a switch in the inner leaf door frame to ensure the ventilation fan comes on whenever the door is shut. Now I've wrapped the cabling in acoustiflex to decouple it at the outer leaf... but I can see that at the door in particular, the cable is 'tight' in the decoupling material on the framing of the inner room. And I'm wondering if this could in fact cause a flanking path and whether I'd be better off having the cabling wrapped in the acoustiflex ONLY on the outside leaf, and to have it packed ONLY with GG sealant where it comes through the framing on the inner leaf. (Of course, if it is ONLY packed with sealant then it's possible the elec cabling will actually TOUCH the inner room framing and thus create a flanking path...but at least the sealant won't hold it 'tight' like the acoustiflex is at the moment. (Acoustiflex is just a proprietary ruberised material from Acoustica here in Australia. I'm also using it to wrap and join the 'broken' ventilation ducting (where it runs between the leafs) and as a mat to sit the silencer boxes on.)

Thanks SO much.

All the best.

P

I wouldn't worry about it too much: you seem to have it under control with what you have done so far, and there won't be much flanking going on with that cable anyway. I think you are probably fine as it is, as long as you can keep it relatively well clear of actually directly bridging the gap.


- Stuart -

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

Hi - and thank you for your response on the electricals...it's very exciting to have this finally taking shape!

I just have a question and comment on acoustic caulk.

Initially I couldn't get the Green Glue Caulk so I used mostly a CSR (fire/acoustic) product when bulking up and then a Sikkens (fire/acoustic) one when that ran out and the supplier was closed for the break.

I then had a case of GG caulk saved for when I finished off the bulking outer leaf and started building the inner room.

And what I've noticed is that where the CSR and Sikkens products have been fine on a single application, the GG caulk is contracting very noticeably on drying and in many places, holes are being left, which then require a second go with the caulk.

I'm doing things exactly the same with the GG product as I did with the others so my question is...

Do you have to do something different/special with GG caulk due to its shrinkage?
Has anyone else noticed the shrinkage?
And how long do I have to leave the first layer of plasterboard and its caulking /recaulking to be sure that it's not going to KEEP shrinking and keep leaving new holes....as I put new layers of plasterboard over the top.

Many thanks for any thoughts and experiences.

Peter

"Initially I couldn't get the Green Glue Caulk so I used mostly a CSR (fire/acoustic) product when bulking up and then a Sikkens (fire/acoustic) one when that ran out and the supplier was closed for the break."

Peter can I ask you to say this again and say it like you are doing it? It reads like you have used acoustic caulk in the same way that you would use the damping compound that is Green Glue.

OR you have used Green glue in the same way that you would use acoustic caulk.

I'm not getting in your business my friend. I am having a bit of an understanding issue in this respect.


If you wouldn't mind?

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

Brien, Green Glue Company does also make an acoustic sealant (caulk), as well as the actual Green Glue damping compound. Confusingly, it comes in rather similar tubes! Or it used to: maybe they changed that.

So it would be good to find out what you are suspecting here: if Peter maybe got the tubes mixed up, and used the compound instead of the caulk? Or maybe the caulk really does contract and shrink as it sets.

Peter, maybe you could call Green Glue themselves, and see if they can comment on whether or not their acoustic sealant (not their visco-elastic polymer damping product) is supposed to shrink as it dries? I've never used it myself, so I can't tell you how it is supposed to behave.

- Stuart -

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