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Discussion Starter · #1 ·
Hi all,


I've just moved in to our new house and we have a dedicated "theater" room on the first floor, indirectly below our kids bedrooms. Of course, the builder did nothing of significance to sound proof the room except use some blown in celulose insulation in the walls.


There is nothing special done to the ceiling, and it includes 6 6" can lights. I'm wondering if it would be worthwhile to tear out the existing ceiling and install insulation (R-19) rsic clips, etc. Basically, I'm wondering how much of a difference this will make on the noise transmitted to other parts of the house directly above the theater.


If it will make a significant difference, I don't mind the additional work and expense, but if it's only a slight change, then I probably won't go through the pain and expense. I could fairly easily sand down the texture and add an additional layer of drywall with green glue but I was thinking that the insulation and rsic channeling would be better?


Thanks,


Russell
 

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You probably need to do both the insulation, clips, double drywall and green glue on the ceiling. You should probably also beef up the side walls with green glue and a 2nd layer of drywall or else you may end up with flanking noise going around your new ceiling.
 

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+1




The ceiling is a big concern as you're suspecting. The can lights should have a backer box fitted to each, or else your ceiling efforts will be compromized.


The 4 side walls would ideally be decoupled. Are the framed walls next to the foundation actually contacting the foundation? Likely not, and if that's the case they are decoupled. The non-foundation walls would ideally be staggered stud, double stud or clip & channel to decouple.


Then the flanking issues of ventilation and doors remain. So a few things to consider.
 

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Discussion Starter · #4 ·
Ted,


The house is on a concrete slab and 1 of the walls to the theater is an exterior wall so it has hurricane bracing rigidly tying it to the foundation. The other 3 walls are interior walls and have a slim foam pad between the bottom plate and the concrete. I would love to have had the walls staggered stud or doubled, but that's not the case. Just a typical single stud framing.


The house has 2 separate A/C systems, 1 for downstairs and 1 for upstairs so there isn't any sound transmission from the theater to upstairs through the A/C vents. The door is going to be replaced with a solid core and a sweep. The sound is actually surprisingly well isoloated on the first floor, but the second floor is a mess.


My big concern is that you can easily hear the movie dialog in the upstairs bedrooms. Of course bass is an issue, but the kids are pretty good about ignoring the bass feel / sound. They are not very good at ignoring the dialog though.
 

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The single stud walls (including your foundation walls) will not isolate as well as the decoupled framing. You can make them really heavy with drywall and damp them, and that will help with the higher frequencies.


You likely have flanking through ventilation or such for dialog frequencies to travel that far.

http://www.soundproofingcompany.com/...cles/flanking/
 

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Discussion Starter · #6 ·
Ted,


I have no doubt that there is flanking going on in the room. There are 6 can lights and absolutely no sound isolation in the ceiling which is directly below the bedrooms.


I don't think it would be through the hvac though because there are 2 separate systems for the downstairs (theater) and the upstairs.


In your experience, will treating the ceiling significantly impact transmitted noise or is it more of minor impact? Just trying to figure out if spending $1500 on sound proofing the ceiling will actually help, or if I will just end up with muffled dialog beaming into the upstairs bedrooms



Is there any kind of a before and after SPL test for treating the ceiling anywhere by chance?


Thanks!


Russell
 

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Even if you have seperate HVAC sound can leak from the opening of the seperated HVAC. If you can get it done for $1500 you will be happy with the expense IMO.


Before spending the money and doing it be sure to do proper research as a small mistake can completely undo what you are paying to do.
 

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Russell, no significant before and after testing is likely. Measuring ambient background noise (so you can subtract that data by frequency), establishing test tones in the exact same location each time, and measuring the results from 80Hz to 4000Hz isn't in a DIY box.


We do this sort of ceiling isolation literally daily for neighbor noise. Works quite well. Generally all the sound that remains is low frequency. Unless there remains a significant flanking path, normal dialog would not be heard.


As previously stated there will be some degree of flaking through the side walls, so very amplified dialog (hollering and screaming on the soundtrack) will likely have some flanking above. Could be a little, or could be a disappointing amount.


This is the risk of a single surface solution
 

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Discussion Starter · #9 ·
adam and Ted,


Thanks so much for the confirmation! I was thinking of using the acoustic caulk for all of the wall plates, hvac, etc, and building boxes for the can lights to help with the flanking.


I'm a bit dissapointed with having to rip out a brand new ceiling, but such is life.


Ted, is there a significant difference between simply adding another layer of drywall with green glue vs adding the RSIC clips and channel?
 

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Yes, big difference. Just the act of decoupling alone will drop your low frequency resonance point and therefore give you better low frequency isolation. It's very big.
 

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Discussion Starter · #11 ·
Again,


Thanks Ted. I'll most likely be giving you a call to discuss what products to order early next week.


Russell
 

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Or just train your kids to sleep through the thunder. When I was a kid we lived under a runway approach. I can't recall ever being awakened by a four engine turboprop 100' off the deck. Not after the first couple weeks, anyway.
 

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Discussion Starter · #13 ·
DMF,


They actually are pretty good about sleeping through rainstorms and such. They're also really pretty good about sleeping through bass. It's the dialog that wakes them up. Something about the spoken words wakes them up and keeps them up.
 

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White noise generator?


Soundproofing? Oh, wait ...





Bass is mostly propogated by transmission through the structure. Midrange too, though it seems to damp much quicker than bass. But I suspect that a lot of what is getting upstairs is leaking out the doors and through the ducting. If the ducting to the upstairs room runs through the "theater" walls, then all that stands between them and the dialog is a layer of interior sheet rock.


Yes, decoupling the ceiling will help, but eliminate all the other vectors first.
 

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Discussion Starter · #15 ·
DMF,


Fortunately the A/C system is all in the upper attic so there are no ducts running through the theater and up to the upstairs rooms. The 3 ducts that are in the theater run directly to the dedicated downstairs A/C system. Also, I tried stuffing a towel below the door to "seal" the door and it had little effect. Outside of that there are no other penetrations in the walls except for electrical and low voltage and all of them have been sealed and surrounded with blown in cellulose insulation.
 

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Jeez, what's your listening level? Measured the upstairs sound level?
 

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If these are low frequencies, then it's structural as DMF mentioned, and not sneaking through cracks and ventilation.
 

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Discussion Starter · #18 ·
DMF,


Listening level was quite normal. My 6yo daughter and 3yo son were in there watching incredibles and I could make out the lines of dialog upstairs in their bedrooms. I don't know off hand what the level was, but likely 50-60db or so? Typical listening levels for kids, no where near reference levels.


The house itself is pretty quiet. We're on a culdesac corner with a big greenbelt behind and no neighbors immediately adjacent. We have brand new variable speed A/C equipment that is very quiet and it's above the second floor in the attic about 15' or so away from the bedrooms.


Ted,


No LFE at all actually. Since we just moved in, the sub etc. is not hooked up yet. Just a pair of 2-way bookshelf speakers I built. I have no idea how the LFE isolation is. I guess I'm not *as* concerned with the LFE as the kids are pretty immune to that.
 

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Ah. I see. That must have been what DNF was referring to. You could chase down possibilities for quite some time, or just build a room-within-a-room as is generally done.
 

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Discussion Starter · #20 ·
We are in the process of doing the ceiling now but have hit a little snag.


First, the channel runs right through my return air duct location (see pic). Can I just move the channel over 8" to the right? It will be quite close to the other channel but will still be less than 48" on either side? Is there an issue having 2 channels less than 24" apart?


Second, how do I handle my hvac returns and supplies? I have flex duct with standard grills for my supplies, but my return is framed into the ceiling (see attached pic).


Thanks for any help. We're basically stalled until we can figure this out.
 
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