So we've got someone coming in a couple of weeks to start finishing our basement. One of the rooms will be my theater - poured concrete on 3 sides, dimensions 11'7" x 20 ish, depending on where the framed wall is going to go. Framing all 4 sides even though 3 of them are concrete, and my only concern is keeping as much noise as possible from reaching the room above. The floor joists are 8'10 high, but there is ductwork that runs the length of the room about 1/3 of the width, dropping height to 8' 1. I was originally planning on dropped ceiling with acoustic ceiling tiles, but I know sheetrock will probably work much better. Problem is, with all that ductwork whats the best way of going about that while keeping it decoupled from joists?

Sheetrock, because of the mass and seals, will work much better than a dropped ceiling.

You would build decoupled soffits to cover the ducts.

Based on your description, it sounds like you have both forced and return trunk HVAC lines running through your intended theater, based on the "1/3 width" of 12' estimate. This is similar to what I had to deal with along my main beam. In my case, I moved the forced air portion (closest to the beam) to the opposite side of the beam it was running along (wall under beam is one side of theater in my layout), and then moved the smaller forced trunk along the beam where the return was. Just got this finished recently. If you can do similar, you will be left with only a 16-18" soffit on one side enclosing one trunk line to deal with, vs. a 3-4' one encasing both trunks. You can then build a soffit on the other side of the room to match.

I plan to decouple the soffits and then cover useing DD/GG. A picture or two might help with suggestions.

Pics would help a lot.

I would suggest moving the ductwork to the perimeter of the room; that way, you could hide it with a soffit.

I hid all of the plumbing and HVAC ductwork this way (and there was a lot!). Plus, it really adds to the theater feel as it allows you to add interesting architectural features, lighting, bass traps, etc.

Good Luck!

If I read your post correctly, you can frame a flat ceiling under the ductwork and still end up with a ceiling height of about 8'. If you can live with that ceiling height, you could avoid moving the ductwork.

To decouple a ceiling while losing a minimum of height, you could install RISC clips and hat channel. It takes some time and money, but the alternative methods of decoupling a ceiling seem worse in most cases.

Have you thought about what you're going to do with the walls? If you decouple only the ceiling, I would be concerned about sound flanking via the walls. Staggered stud walls are within the skill of most any carpenter and don't take much additional labor.

Good acoustic reasons for the soffits as well as being interesting architecturally

Framing all 4 sides even though 3 of them are concrete,

Looks like double walls

thanks for the replies and sorry for the long delay. Here are some pics of the space; as I stated above 3 sides are concrete (with some framing where it's above ground). I'm doing full framed walls anyway, but the ceiling is going to be drop. That is not going to change, so if anything else I try to do will be a waste just tell me. Should I bother attempting to isolate the walls from the joists? should I bother doing a staggered stud on the one wall that faces the rest of the basement?

http://i789.photobucket.com/albums/yy177/klpardo/basement1.jpg

looking out

http://i789.photobucket.com/albums/yy177/klpardo/basement2.jpg

With a drop ceiling do not waste any money on sound proofing. If sound proof matters to you, reconsider the drop ceiling.

There you have it.

ugh - nothing? stuffing the ceiling with insulation? Adding sound deadening to ducting? I already have 1 1/2" acoustic tiles....

Those efforts and expense will prove costly with very little benefit. The dropped ceiling will define the results

Insulation will help a smidge with the upper range of the sound spectrum. But so what, you will still hear the rest almost crystal clear.

Drop ceilings are designed to be relatively quick, cheap alternatives for office spaces, professional buildings, etc.

They have no place in homes, much less in HTs. :D

The "acoustical" drop ceilings are designed to absorb sound at around the human speech spectrum...to reduce noise in busy office environments. That is exactly the opposite of what you want at home and in a HT.

OK - so if I go with drywall ceiling, what next? I'm very budget limited here, is it worth trying to soundproof walls that face the outside?

Ted has a vast resource of materials that you need to read through. All sorts of tidbits that are important when you start talking about sound isolation. I'm sure he could provide lots of links at this point to articles which will show you very clearly the power of sound waves, weak points, flanking etc. etc.

OK - so if I go with drywall ceiling, what next? I'm very budget limited here, is it worth trying to soundproof walls that face the outside?

Basically look at your room as an aquarium. If you have a hole in your aquarium (it doesn't matter what side) water will leak out. Sound is much the same way. That means you want to decouple and DD/GG all four walls and the ceiling. The walls facing the cement just attach to the joists using RSIC -4 clips. The Interior wall you build stagger studded. Ceiling is done with clips and hat track. Avoid all wall penetrations like outlets and especially can lights. There are special build techiques you can use if you still want can lights, but it does take some planning (build backer boxes or build them in a soffit).