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Discussion Starter · #1 ·
I insulated my ceiling leaving one inch of dead space and I installed the first layer of 1/2 inch dywall. I caulked, taped and used 2 coats of joint compound. I have recessed lighting but I built boxes out of 3/4MDF for them to go in.


I am disappointed with how much sound is still coming through the ceiling from my family room above with the 1st layer of drywall. Will the 2nd layer of drywall make a minimal or dramatic difference?
 

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I am disappointed with how much sound is still coming through the ceiling from my family room above with the 1st layer of drywall. Will the 2nd layer of drywall make a minimal or dramatic difference?
Is this a basement HT? What kind of sound is getting through? Is it mainly the low bass, or can you clearly hear the vocal range as well?


Another layer will add alot more mass and help across the board with sound control, but if you have other leaks then you need to take care of them too. I have a basement HT and two layers of rock on the ceiling and all I hear upstairs is the bass. Its not bad but you can still hear it a bit. De-coupling is the only practical way to get rid of that. Adding mass will of course make a big improvement though.
 

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The fact that you attached the first layer to the existing joists is a great deal of the culprit. Also, you could have sound "flanking" the ceiling and going through the walls and then up.


Ted
 

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Discussion Starter · #4 ·
Yes, this is a basment HT. I can hear voices coming through the ceiling.

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The fact that you attached the first layer to the existing joists is a great deal of the culprit.
I had no choice with attaching the drywall to the joist. I have a soffit running the width of the room. I have double drywall and insulation on the walls. The sound is coming through the ceiling not the walls. I am going to go ahead and add the 2nd layer of drywall and hope for the best.
 

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Ok if tis the ceiling, the second layer will help out alot. I went so far as to use ASC Wall Damp squares between my two layers (ceiling only) to dampen the vibration transfer to the joists. Its not as drastic as using RC but it will help dampen that bass vibrations while not affecting the in-room acoustics as much as RC. I hear nothing but some low bass and I only have a single layer of rock on my walls.
 

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What about your HVAC? Do you have any runs in the ht room? Did you use flex ducts for the runs into there? The HVAC ducts can carry sounds to the whole house quite easily.
 

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Discussion Starter · #7 ·
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Originally posted by CV63
What about your HVAC? Do you have any runs in the ht room? Did you use flex ducts for the runs into there? The HVAC ducts can carry sounds to the whole house quite easily.
I have to flexible runs with the joist and part of the main AC unit duct runs along the joist. I used R38 insulation and I used blown insulation where the flexible runs are. I built a soffit of double drywall, blown insulation and R38 between the joist over top of the AC duct. Everything is rock solid and air tight. The only are I screwed up on was the outlet for my projector on the ceiling. I am trying to think up a way to seal it better.
 

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There may as well be a viewpoint from the camp of The ARO (anal retention and overkill), which I happen to be the Chairman of. I'll be building "Dead Vents" to contain the sound.

http://www.tedwhite.homestead.com/Ducts.html


Ted
 

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Hey Ted, I saw something cool in a mag. Mufflers for HVAC. Works the same as a car muffler. Surprised I havent seen anyone here build something similar.
 

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I'd use mass loaded vinyl. www.acoutiblok.com sells it but you can get it much cheaper at www.silentsource.com. One 20 foot by 4.5 feet roll will cost about 135.00. I would install a layer of this, then add the second layer or drywall. That should solve your problem. A single layer of mass loaded vinyl has more sound blocking ability than two sheets of drywall.
 

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Another option is to simply not connect the ductwork to the HVAC system. Simply use it to circulate air from another part of the house into and out of the HT by using variable speed inline duct fans. This is a relatively simple and cheap solution that has worked well in the past for me and is working today in my own HT.


If your MAIN AC line is still metal, that can be an issue too, even with all the work you did, it doesn't take a lot to get that tin vibrating and it seems to be self amplifying. Probably too late to change that now. For future reference, if you replace it with one made of duct board, there is a trememdous difference in sound transfer.


I actually modded my other ductwork (non HT) that passes through the ceiling to be a combination of ductboard covered with rigid fiberglass and then filled in the gaps with loose fiberglass.
 
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