Soundproofing advice for my setup

Discussion in 'Home Theater Projects' started by zuhl, Jan 22, 2014.

  1. zuhl

    zuhl Auditioning

    Jan 22, 2014
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    After searching for answers on the internet, I figured it would be best to just post on this forum and ask the question.

    I have a new 1.5 stroy house that I built on time constraints so I was not able to do all the cool soundproofing featuers I wanted. I have a room on the second floor that is designated to be the future home theater. It has no windows, and has three of its four walls facing empty attic space. All four walls are 4" walls insulated with blown cellulose. The door to the main house is a solid core interior door with gaskets (but no threshold). The walls facing into the attic are covered with Blue 3/4" XPS foamboard for extra insulation. I sealed all cracks and gaps with caulk for air-tightness. The cieling of this room and of the first floor has about 22" of insulation which is a combo of fiberglass and cellulose. The floor is carpet with an 8lb pad with a 1.5" toungue and groove plywood subfloor.

    I would have loved to put in clips, two layers of sheetrock with green glue, etc, etc. However, to get in the house in time, we had to simplify and move on. Now I am looking for ways to upgrade this room without breaking the bank.

    I have a crappy little all-in-one theater system in there now and mostly just play music for my kid to hop around too. Overall, the amount of sound that leaks from this room is reasonable. The insulation in the walls and solid door do a good job for starters.

    I think that having 3 of the walls reverb into the attic helps since the attic has so much insulation in it.
    So I am trying to figure out what to do next:

    Maximum: Tear out trim and carpets and add another level of sheetrock with green glue all around. Under the carpet add another sheet of plywood (or soundproofing board) with green glue, then re-carpet. Add sill to door.

    Minimum: upgrade just the one wall that faces the living areas of the house. Let the other three walls reverb into the insulated attic. Pull up carpet and drop some MLV underneath and lay it back down.

    I have also considered adding layers to the attic side of the three walls. I called green glue to see if I could add a sheet of plywood over the XPS but they said it was not recommended.

    Any thoughts on my approach in this particular case? I would like to start small and work up big, unless going small is not worth the effort.

    Thanks for all your help.
  2. schan1269

    schan1269 HTF Expert
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    Jul 4, 2012
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    Buy some acoustic cell spray foam and just inject it into the walls.Yes, there are products called...Acoustic cell in-wall spray insulation.
  3. Bobofbone

    Bobofbone Stunt Coordinator

    Jan 24, 2010
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    Is your home stand alone, or connected to other houses? If it is a single house, your needs probably won't concern neighbors. When will you be using your system? Is sound a problem for the rest of the household and other people?

    The first thing I'd do, and the cheapest way, would be to set up your system in the room and fire it up. Put it at the level you want, and then go through the rest of the house and see how much sound is coming out. If it isn't objectionable as is, that's about as cheap as you can get.

    Assuming you want to reduce sound, I'd take care of any areas of sound leakage first. HVAC systems can transmit sound through the rest of the house. Undampened ventillation ducts, especially ones with a straight shot elsewhere transmit sound. When I designed my set up, I had no direct duct work from the HVAC system coming into the area, and the duct work in the ceiling used flexible internally dampened ducting with curves in the path it took. Blocking duct work into and out of the room may help.

    Doing something to the wall common with the living space may help. If you use the foam, you might want to place any additional wiring for your system before filling the area with foam. The other possibility would be to put a layer of 5/8" drywall on the atic side of the walls. you would'nt have to make it look pretty. That would have some impact, but not alot. You might also consider sealing any junction boxes and switches with putty packes or a weather seal.

    All of the suggestions above are relatively inexpensive. You have also done most of the simple things to reduce sound to other rooms, from your description. If the walls and floor still transmit too much sound, the solutions start to get more expensive. Tearing up your floor and redoing it probably won't do much. you have already dampen the area somewhat, and the additional measure that would decrease sound transmission to the room below might be to treat the ceiling of the room below with sound isolation clips, hat channel and double dry wall with green glue. That's more trouble and expense, though..

    One other low cost possibility. In the past, when I got complaints, I used to use headphones when everyone was in bed. But, at that time, the area I used had almost no measures to treat sound.

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