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Discussion Starter · #1 ·
We are building a HT in our new house (we are at the framing stage - getting near to being done). After a lot of research, I have decided to soundproof using green glue between two layers of drywall (I saw a pretty convincing video on YouTube of how well it works - and drywall is cheap cheap cheap right now!)


HT is upstairs (in Houston, there are no basements), and one wall is the outside wall, and another wall and ceiling are to the attic area. So I really only need "soundproofing" in the usual sense on two interior walls and the floor.


My question is - if I soundproof only part of the theater and not the rest, will I regret it from an acoustic perspective?
 

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Quote:
Originally Posted by plasmawoman /forum/post/18231658


My question is - if I soundproof only part of the theater and not the rest, will I regret it from an acoustic perspective?

You may regret not doing the whole structure. Surfaces (walls) that are left untreated are flanking pathways: http://www.soundproofingcompany.com/...cles/flanking/
 

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What do you mean acoustic perspective? Are you talking about audio quality, or sound containment? Sound proofing is an all or nothing thing imo. Adding some insulation and double drywall will help, but you wont get really good results unless you treat everything. I decided against it in my theater, but I did add r19 in the ceiling and did a 2nd layer of drywall. I didnt bother with the green glue or whisper clips because I didnt have the budget for it. The extras did help a little bit with highs, but lfe leaks out of my ht without any issue.
 

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Quote:
Originally Posted by plasmawoman /forum/post/18231658


My question is - if I soundproof only part of the theater and not the rest, will I regret it from an acoustic perspective?

You are not going to get the results you expect - when it comes to sound proofing you have to think in terms of "the weakest link". Using double drywall and Green Glue (DD+GG) is the last step in a whole sequence of steps necessary to acoustically isolate a space. If you don't do the whole thing then the DD+GG is wasted money and effort.


The Sound Proofing Company has a library of soundproofing articles on their web site that talks about the steps necessary to soundproof a room. You can educate yourself there about what will (and won't) work for your space.
 

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Quote:
Originally Posted by plasmawoman /forum/post/18231658


if I soundproof only part of the theater and not the rest, will I regret it from an acoustic perspective?

Green Glue is a terrific product. But that has nothing to do with the quality of the acoustics inside the room. Good in-room acoustics requires bass traps and other acoustic treatment.


--Ethan
 

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One thing that comes to mind is that if you don't treat the outside walls, you might end up watching a movie and then suddenly get distracted by the sound of your neighbor mowing his lawn.... Sound proofing goes both ways
 

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Quote:
Originally Posted by Ethan Winer /forum/post/18235714


Green Glue is a terrific product. But that has nothing to do with the quality of the acoustics inside the room. Good in-room acoustics requires bass traps and other acoustic treatment.


--Ethan

Although you can argue if you can hear your neighbor's lawnmower, kids playing in the street, or your furnace roaring, it's not going to do much for the room acoustics either.
 

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Discussion Starter · #8 ·
Maybe I should phrase it this way: Soundproofing could be described as keeping sound IN the room that you want in the room, or keeping it OUT of other rooms where you do not want it. If the benefit of soundproofing is keeping sound out of other rooms (like adjoining bedrooms), then the biggest value is in soundproofing common walls, right? But if the real value of soundproofing the home theater is keeping the desired sound IN the theater, then I would want to soundproof everything.

Does that help any?
 

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You're going to "fill that room up" with sound. You're going to fill an aquarium full of water. It doesn't matter which wall (floor, side, etc) you build from plastic wrap, when that water comes pouring out of the aquarium, it's getting everywhere in the house. So you treat a common wall ... the vibrations get to the roof joists, which rest on the outside wall of the bedroom, and, you have sound in the bedroom ... through the floors, ceiling, attic, places you would not expect. A one or two sided aquarium is rather worthless.


Sound in or sound out. In the overall scheme of things, it doesn't make much of a difference. The isolation techniques used in typical construction are not one-way devices. On the other hand, isolation to reduce sound transmission out of the room is harder to do than the isolation required to prevent environmental sounds into the room (unless you live next to Hobby, Sugarland Airport, etc.)


A traditional metric is you don't want to raise the noise level in an adjacent space by more than 3dB. So if the ambient noise level in your room is 33dB (not unusual), then outside your room, you don't want the noise level to get above 36dB when you're playing your system. The usual sound track is recorded with a dynamic range from 22dB to 105dB (115dB for LFE). By that metric you have 105dB - 36dB is 69dB ... good luck. Even with GG, DD, Clips, Isolation, careful HVAC work, etc, etc, you're not going to get there from here unless the crew building that shell is expert in building isolated rooms. (Just as a reference ... going from 33dB SPL to 36dB SPL is a doubling of SPL.)


Let's go the other way ... ideally, you'd want the noise floor in your room (equipment and HVAC running) to be 21dB (just below the softest sound recorded on a CD, DVD, BD) so you can hear the softest sound without turning up the volume (and making your sound isolation problem even harder). If the ambient noise level in your home is 33dB, then your isolation requirements are 33dB - 21dB = 12dB ... a much easier problem to solve...but, even at that, it isn't going to be solved by half way measures.


Does sound isolation affect in room acoustics. Yes; but, indirectly. You have comfortable listening levels, enhanced dialog intelligibility, you're not running your system at levels upwards of 8 times intended volume (to raise the quietest sound above the background level), running your equipment to distortion and you don't have to buy as many bass traps from Ethan.
 

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Holy crap that is nice!





I come from a commercial construction background and I can tell you that sound will come though any available crack. Often, office walls will butt right up to the windows, there is a small gap that is usually filled with some type of expanded foam tape or weatherstrip there as you need to allow for some expansion and contraction at the aluminum mullions.


Eventually this will dry out and leave a gap or maybe it was not installed correctly. It almost sounds as if there is a speaker right there the sound comes through so much. It can even seem worse if the wall is insulated as the walls allow less ambient type sound in and the point source becomes more pronounced.
 

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Has any testing been done as to just how much sound is transmitted through flanking noise? Something like, do up a whole wall with staggered studs, insulation, DD and GG, treated outlets - what dB loss does that achieve vs treating the entire room? Articles at the soundproofing company's website estimate treating only one wall leaves 5-30% of the sound to pass through as flanking noise, but I don't see any hard figures.
 

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Every structure is different, hence the 5% - 30% variable. Also, that particular scenario is most appropriate to neighbor noise. Someone in a condo looking to treat just the ceiling or a single wall.


In a theater, there is so much sound being dumped into the framing that if you want accountable isolation, you'll follow the aquarium analogy. Treat all surfaces.
 

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Quote:
Originally Posted by Dennis Erskine /forum/post/18240978


Here's a Houston attic conversion (over the master bedroom) ambient noise level is 18 (NC18). Can be done. We did the construction. Just FYI

I can't get enough of that ceiling...the artist who painted that is a total genius, very special room that one.
 

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The painting was the easy part ... figuring out the crosshatch pattern to be the same size throughout and meet in the corners just about drove her off the deep end.
 
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