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Discussion Starter · #1 ·
I have little knowledge in this area, but I need to figure out pretty soon what, if anything, I'm going to do about insulation/soundproofing (partial at best) for my basement HT.


The HT room won't even be an enclosed separate room due to practical considerations of using other areas of the basement for other purposes. (In other words, low WAF, although it was ultimately my choice and the conflicts were pretty much all due to things I wanted anyway. But I digress... )


Anyway, the room is a step-down room, as is the room directly above it, so it does have a beginning and end in that sense, it's just that the walls only come back part way on the sides, and it's open to other areas (bar, game, billiard rooms).


So there's no way I'm even concerned about soundproofing it entirely, but I am hoping to do something to reduce the volume of sound to the other levels of the house. I'm mainly thinking of is doing something with the ceiling of the HT room and possibly the other nearby ceiling areas, but I don't even know what. I think a lot of the things I've read about in here would be a waste of my time and money, since there's no way I'll accomplish any real degree of soundproofing. Still I'd have to think there are a few things I could do to get a worthwhile measure of results.


I'd be grateful for any advice. I don't want to have this theater all complete and still have to keep the volume down at night, like I do now in our family room on the main level. Thanks!
 

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Sounds like you've already taken one of the most effective steps in keeping the HT as far away from bedrooms and other areas you don't want to disturb.


It sounds like your room is already finished? If not, then there are a lot of options open to you. If it is finished there are some things that can be done, like adding insulation in accessible areas such as the ceiling and walls (if you have a suspended ceiling). Doing this will not only reduce sound transmission but help eliminate resonances in these hollow areas. Insulating duct work can also help as can using a solid door to the basement.


In the long run you should be able to keep mid and high frequency sound confined to the basement, but low frequency energy is likely to be transmitted through the home's structure to other areas no matter what you do. Confining LFE requires isolation and mass.


Best of luck with your new HT!
 

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Discussion Starter · #3 ·
Actually, no, the framing on the basement just started two days ago. The reason I know I won't be able to accomplish any serious soundproofing is that we've decided that the theater will be part of an open rec room area.


So the ceiling is completely accessible, as are the walls. The existing insulation is attached to the foundation walls, and the studs are up against the insulation.


I think the ceiling is my best bet. What type of insulation would be appropriate for soundproofing? . A friend of mine (not an expert on the subject) suggested that insulation (a solid) might carry the sound more than empty space would. The ceiling will be drywall, if that matters as far as what type of insulation to use. Maybe the walls too but I wonder if it'll be worthwhile considering there's already insulation behind the studs on the foundation walls. I was also thinking the walls on the side of the staircase, which is basically the back wall of the HT.


I think that a solid door would have a low WAF. Besides, the cats need free access between levels. I guess this is more like sound-reducing, rather that sound-proofing, but I have to think it can't hurt (except my wallet).
 

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Discussion Starter · #4 ·
Also, is there anything I should know about installing the insulation? I.e. would you do anything different installing it for soundproofing vs installing it for thermal purposes?
 

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I would install insulation in the ceiling (between the floor joists above) and in all the exterior and interior walls of the theater and rec room area. fiberglass batts should be fine. In addition to increasing the STC (sound transmission class, a measure of how well a material or construction method blocks sound) of the construction it will help reduce resonances that can and will occur in sealed open spaces like wall and ceiling cavities.


In my own theater, I initially left the one interior wall uninsulated. It would resonante audibly. There are several pictures hung on this wall, the resonance caused the picture hangers to vibrate out of the walls and sent the pictures crashing. I then filled the wall up with cellulose insulation and the pictures now hang straight and stay put.
 

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Discussion Starter · #6 ·
Thanks mysphyt, very helpful. Are fiberglass batts the kind that come in rolls? What did you do where ductwork was going through the walls and ceiling? I would think that's a key area to insulate, but also a tricky one due to the space being taken up already.
 

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Hi Jeff,


Chris has offered a lot of great advice, so all I might do is add to that. There are two things you must address when trying to achive higher audio isaolation or STC (sound transmitivity coefficient), they are airborn and conducted sound. The airborn sound is isolated using very frequency specific layers of different types of materials such as fiberglass bat, drywall, osb (oriented strand board), rigid insulation (styrofoam), or semi-rigid insulation such as Owens Corning series 200 to block the sound. All of these materials have different band widths and frequencies they will help stop, so layering them in various configs. will prove to be very helpful. Conducted sound requires ISOLATION, in other words "air space" or low conductivity insulators to break the chain, such as closed cell foam or RTV. This might sound like a lot of work... it sort of is but it is very worth while. Second thing to understand is you will try to do two things acoustically in the room itself: absorb, and diffuse. Usind a material such as OCF 200 will "quiet a room down by absorbing specific frequencies, and a diffuser (uneven surface) will break-up a wave and make it more manageable. Remember any gaps or holes leak sound big time when sealing a room. I hope all of this helps, I have tried to put technical info into understandable terms since I am not aware of you backgraund or areas of personal expertise.....Good luck and most important HAVE FUN!


Steve Walker
 
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