VO-BB - 20 YEARS OLD!

[Mike Sommer]

Since all the walls are rigid construction, at this point decoupling the drywall would be not worth the expense. Besides he would need to decouple the ceiling too. This is very expensive and he does not have the head room for it.


Expanding foams are acoustically transparent. Great for thermal but do nothing for sound. The purpose for using a non hardening caulk, like Sikaflex 1A, is to make the room air tight. Foam might help for really large gaps, but foam can fail.

All that is needed in the wall cavities is standard fluffy insulation. Since drywall is acting as a bass trap on our walls, the purpose of the insulation is to slow and transform resonance into heat.


Mathematically a fully treated wall serface with 4" of ridged fiberglass insulation can only reduce loudness levels by about 6dB's (exactly the same as a sheet of 5/8" sheet of drywall). This is why air locks are generally treated with rigid insulation- but it is doing so by reducing the volume increase created echos and comb filter. Dollar for dollar the dry is cheaper. Even cheaper is Quiet Rock, which is about the equivalent to 4 layers of 5/8" drywall - in terms of noise reduction.
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The Blog:
http://voiceoveraudio.blogspot.com/

Acoustics are counter-intuitive. If one thing is certain about acoustics, it is that if anything seems obvious it is probably wrong.

[Mike Sommer]

[cyclometh]

So from that image, it looks like tear out the ceiling drywall, put in two layers of 5/8" drywall between the joists, and put in standard pink insulation.

Then rehang a drywall ceiling over it?

Foot falls can be an issue, unfortunately. I generally just ask people not to tromp about.

Edit: There is also at least one duct in the ceiling, and some pipes going to the bathroom upstairs. Might make it problematic to install drywall in the manner described.

So many things to consider.
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Corey "Vox Man" Snow
http://voxman.net

[Frank F]

Go for it Mike. Although you are not correct on decoupling, nor foam insulation - I will not argue the point, as I do not wish to confuse the issue further.

Good luck on your project Cyclometh.

frankf
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Be thankful for the bad things in life. They opened your eyes to the good things you weren't paying attention to before. email: thevoice@usa.com

[cyclometh]

I've gotten a lot of good feedback and resources from people both here and in offline discussions- thank you all very kindly for your insight and suggestions.

Once I actually tackle the job of doing the thing I'll probably post pictures and suchlike here, so you can look forward to that.
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Corey "Vox Man" Snow
http://voxman.net

[Mike Sommer]

Frank, if the man wants to tear the whole structure apart, then he is certainly welcome to. But from Corey's description he is only having problems with some low vocal frequencies being carried through the walls- walls that are not insulated and only have 1/2" drywall on them -- as I predicted and has been verified by Corey in his latest email to me.

With that information, simple steps can be taken to give him the isolation needed from low frequency vocal transference or bleed, without ripping the whole house apart. Besides what does he do about the rigid ceiling??? 1) He does not have the room for more structure (a room in room) and 2) Unless he wants to reframe the entire basement to decouple the walls (because all the walls are inner connected) it makes no sense. All he will gain is 6 to 8 dB's more of reduction. He can get 6 dB's with and extra layer of 5/8" drywall or 24 dB's of reduction with a single layer of 1/2" Quiet Rock over a single layer of "Type x" 5/8" drywall.

With what I've prescribed he can easily achieve 45dB's, which should be more than enough for what he's dealing with.

If there was a problem with low frequency machine rumble or sound levels above 75 dB's, then yes, bigger steps would need to be taken. But this is a matter of simple vocal transference.

Now he can use RC-1 or RC-2 Resilient Channel to hang the drywall on the walls, but he is going to run into a problem with the the door because he may not have room for the inch that is needed to hang channel and the drywall. ( Corey all these layers eat up space, so check and double your clearances with your door opening when you frame out the opening when you go to a bigger door. Rule of thumb: the door frame opening needs to be 1-1/2" larger than the door width and 2" taller than the height. )

Even if Corey uses RC1 or RC2 channel, there is still the matter of the ceiling, because this kind of channel can not handle the load being placed on the ceiling. This would require a floating ceiling, and that is a completely different matter.

With further understanding that there is a bathroom directly above this space, we can gather the there could be a real problem with foot fall and water flow. But luckily there is another bathroom on the other side of the house that can be used- and if the family likes to eat, they can use the other bathroom while daddy is working. But the added mass on the bottom of the floor and insulation between the joist, the most serious noise problems should be taken care of.

So to me Frank, there are a lot of things that you are not taking into account. And until the drywall is pulled down, there may be many more that need to be dealt with. Because this is a home built with only structural integrity in mind, not for a sound studio, and these two types of construction have two completely different requirements for the final outcome. I deal with these two different worlds every day, and it's understanding what the real problems are, that get us to practical usable solutions. So in this case, it's not what you don't know that will really get you... it's what you don't know that you don't know.
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The Blog:
http://voiceoveraudio.blogspot.com/

Acoustics are counter-intuitive. If one thing is certain about acoustics, it is that if anything seems obvious it is probably wrong.

[cyclometh]

The ceiling is currently 7'6" to the drywall above. If I wanted to go with a room-in-room option, it would be potentially doable with joists running between the floor joists above offset an inch or two down, sitting on walls with a 2" gap to the current exterior walls. The resulting dimensions would be 10'6" w x 9'4" l x 7'1" when accounting for two layers of 5/8" drywall.

Realistically it'd probably be a little lower beacuse there's wiring and stuff above so the height would have to come down to slip under that mess. Also, the room gets more than 10% smaller in square footage.

However, even a 7 foot ceiling is pretty low for a guy who's 6'4". I'm also not sure it'd meet code. And it would be quite an undertaking- certainly within my capabilities but not necessarily within my desires.

So, I'm currently scrapping the room-in-room option. I only wanted to explore it to make sure I understood all my options.

My current plan, subject to revision as I do more research:

* Tear out drywall on ceiling and walls, clean up and replace old fixtures- the electrical sockets need replacing and this is a good time to do it.
* Block out spaces between joists, caulk and seal everything, mechanically isolate or dampen any wiring, conduits and piping.
* Hang two layers of drywall against underside of floor above and in between wall studs against exterior surface.
* Caulk and seal all cracks, etc.
* Install insulation (rockwool?) between studs and joists.
* Hang two more layers of 5/8" drywall, offset.
* Tape, mud, install new electrical fixtures, and paint.
* Profit!

Notes:

Use Green Glue between drywall layers?
Insulation type? Rockwool or just pink fluff?
_________________
Corey "Vox Man" Snow
http://voxman.net

[Mike Sommer]

[cyclometh]

Edit: I'm an idiot. I was looking at one package of 6 rockwool batts and calculating it as though it was one.

Looks like I could get enough rockwool batts to cover the room for a few hundred dollars. I need to sit down with a spreadsheet and do all the math this weekend.
_________________
Corey "Vox Man" Snow
http://voxman.net