Ceiling gap used for acoustic treatment?

RichHead · Post by **RichHead** » Fri Oct 31, 2003 6:17 am

Hello everybody. I posted this over at homerecording too, so I am just going to steal my terribly worded question along with a picture here:

Use Ceiling Air Gap for Sound Treatment?
Ok folks, I am going to try to ask my question the best I can without drawings (I am at work...shhh). In my small soon-to-be studio, I have a recording room that will be my isolation room (approx 9 by 10). For a little better isolation I am building another ceiling (for the double mass effect) approx 8 inches below my current ceiling, but just on the isolation area. My mixing area will have stock height 8' ceilings.

I plan to use the cavaties in the wall facing the mixing area for sound treatment (yes I plan on doing the same thing on the other side). Basically like the inside-out wall design. I know this will cut down on my isolation between rooms quite a bit, but this does not concern me that much.

The way I am thinking this is going to happen, this 8" gap between the ceilings (with 2 x 6 studs in it) COULD be open to my mixing area as well. Could this 8" by 9' deep cavity serve me any purpose as far as sound treatment? Or should I just wall over it and forget it? I'll try to draw a picture if neccesary.

Thanks for your time

knightfly · Post by **knightfly** » Fri Oct 31, 2003 10:39 am

I'm not quite sure what you're trying to accomplish - if you open the ceiling of the "isolation" area into the mix area, then you don't have "isolation" - you may as well just open the door, or nearly so.

If you're concerned with noise through the ceiling, you need to maintain your isolation - "For a little better isolation I am building another ceiling (for the double mass effect)" - if that's what you need, then you need multiple layers of mass in each leaf of the barrier, with as much insulation as practical between them, the lower one on Resilient Channel, and everything SEALED with acoustic caulk.

Any gaps, and you've built a bass trap instead. Not a bad thing, but not what you said you want.

Are we BOTH confused enough yet? I know I am; it would help if you could just state your main and secondary goals for the space - usually, you have to either compromise or choose... Steve

RichHead · Post by **RichHead** » Fri Oct 31, 2003 1:11 pm

I guess what I am asking is, can I use a 9' deep, 24" wide, 8" tall cavity for any effective type of acoustic treatment. Forget I said anything else....lol

The contruction of the room is going to be too complicated for me too explain propery and maybe is just confusing the issue.

Is that better?

- RichHead

knightfly · Post by **knightfly** » Fri Oct 31, 2003 6:52 pm

Might be a localized bass trap for 31 hZ if the 8" x 24" is what's exposed to the sound, and you covered that opening with 4" fiberglas board; I'm still not sure what you're asking - are the ends of these 2x6's that are over your isolation area still open to the studio? Is there just ONE of these cavities, or are you wondering about ALL of them?

In that location, if they're ALL open and the bottom is closed in (isolation room ceiling) then you might see some good low bass trapping by putting rigid fiberglas across the ends of the joists. The corners are where you get best use of traps, so it might work... Steve

RichHead · Post by **RichHead** » Sat Nov 01, 2003 4:16 am

knightfly wrote:Might be a localized bass trap for 31 hZ if the 8" x 24" is what's exposed to the sound, and you covered that opening with 4" fiberglas board; I'm still not sure what you're asking - are the ends of these 2x6's that are over your isolation area still open to the studio? Is there just ONE of these cavities, or are you wondering about ALL of them?

In that location, if they're ALL open and the bottom is closed in (isolation room ceiling) then you might see some good low bass trapping by putting rigid fiberglas across the ends of the joists. The corners are where you get best use of traps, so it might work... Steve

Yeah Knightfly, I am wondering about all of them. There are 5 cavaties total. Of course its all open up there so it essentially one big cavity with 2 x 6's in there.

They don't have to be open to the studio, but I can make it that way. I only have the framing up right now. Just wondering If I should drywall over that as I go along.

Actually, the cavities vary in depth (8-9') because of the angle of the wall. Would a better picture help? I don't really have a way to detail it 3-D, but I could try to make something better. Maybe just a picture of the cavity?

But you think just treating the area as one big cavity and placing 703 fiberglass across the entire area of the exposed studs might be effective? Hmm....Interesting. Maybe this will have to be one of those "try it and see" deals.

knightfly · Post by **knightfly** » Sat Nov 01, 2003 9:33 pm

that wouldn't be too difficult to try - if the fiberglas across the ends doesn't work (like not enough isolation thru the ceiling) you could just finish closing that section up and making that a double leaf ceiling for the isolation room... Steve