In my basement room, 12x21.5, I am insulating between the "quiet floor" floor joists with insulation and placing cloth over this as my ceiling to keep reflections down. Q. is, I have 12.5 inches to insulate there and I would like to keep some sound from making it's way up into the room above. Should I put sheet rock between the floor joists to create some mass or sheet-blok? I know it will be a little time consuming but down the road, my family may appreciate it. Also, would two layers of drywall equal the single layer of sheet-blok?

Sheet Blok specs are superior to two layers of drywall. From experience, I'd say it's more effective in the low frequency range than drywall. Filling your gaps between the joists is not such a good idea, IMO. I'd suggest filling between the joists with insulation, then building drywall with another layer of drywall on a resilient channel to isolate. Seal all those with acoustic caulk.

Thanks Matt, I do want to insulate between the joists but wanted to avoid a drywall ceiling to cut down on reflections in room. It will have a laminate floor and T1-11 siding on the walls.

Insulate the cavities for sure. Do NOT use RC. While decent for isolation, it is TOTALLY unpredictable in terms of in-room response. RSIC-1 and hat channel is a far superior solution both in terms of isolation and predictablity.

If you want isolation, you need drywall ceilings. If you're going to do a drop, don't bother with wall iso. You'll be wasting money as the sound will go right around those nice iso walls and up and around via the ceiling.

Bryan

I don't know what RC is? I don't know what RSIC-1 is either? As for the ceiling. What I am suggesting is, drywall between the floorjoists, laid flat against the floor above. Would this not accomplish the same iso as the drywall connected to the bottom of the joists in my room? Thanks for the replies!

Getgo - No, it would not improve the sound transmission much to pack drywall between the joists. Mass, space, mass is what stops sound.

RC=Resilient Channel
RSIC-1=http://www.pac-intl.com/rsic.htm
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-->Interesting note about resilient channel, Bryan. I can see why it would do so, though. It could kind of act like a membrane, right?

" Mass is what stops sound" This is exactly my thinking (however twisted it may be)
If I attatch a couple layers of drywall to the bottom of the floor (which is actually the "true ceiling" height of my room and then insulate, have I not created mass in between the lower room and the upper room and filled the cavity between joists in order to absorb sound and curb the reflections in the lower room? I have a headache now.

Mass + air (space) + Mass = less sound. That's what I meant it to read.

The idea with the drywall ceiling mounted on RSIC-1 and hat channel is that you have a hard dense layer that is physically decoupled from the rest of the structure. You also will then have a nice insulated cavity between them. Both things improve isolation.

If you simply put drywall on the underside of the floor above, you're not really gaining any physical isolation as they're attached rigidly and with no insulation in between.

The RSIC/Hat/Drywall solution allows the ceiling to float somewhat providing a good isolator AND a decent absorber at a portion of the bass frequencies.

IMO, the best solution if you have the budget is RSIC-1 with hat channel, then drywall, then a layer of Audio Alloy Green Glue (an elastomer damping compound/glue combination), then another layer of drywall. Fill in the cavities above with insulation and that's about as good as you're going to get without physically constructing an entirely new 'room in a room' with floated floors, new joists above, etc.

Ok, now my head is really starting to hurt.

I am starting to slowly understand that simply adding mass to the floor underside will have no effect on isolation to the room above. Bummer.I don't want to drywall the ceiling of the room, just dead against it, hate the stuff. Maybe insulate the cavity and go with a drop ceiling and hope I get some isolation and absorbtion at the same time? Or just give up and go back to my other hobby of riding a Harley?(It's actually cheaper!)

Well, doing that will definitely get you some isolation - at mid and high frequencies. It will also provide some bass absorbtion inside the room. It will do almost nothing to stop bass getting in or out.

If you want the drop ceiling and help a little bit with isolation, beef up the hangers for the ceiling track and in addition to a GOOD solid ceiling tile (not just the vinyl faced fiberglass), cut drywall squares to place on top of the ceiling tiles. That adds mass at a decoupled point and far from the floor. That will help some bass transmission but reduce the absorbtion inside the room from the ceiling cavity in terms of bass.

Bryan

Thanks Bryan, How about the sheet blok on top of the ceiling tiles instead? Might I get good results this way and retain some ceiling height inside the room? I'm not against the sheet rock panels above the ceiling tiles though. It would be cheaper too.

You can use MLV (sheetblock) if you want. In fact, you can do both.

Hang (loosely) the sheetblock from the bottoms of the joists above after filling cavities with insulation. Then do the drywall on top of the tiles. The only thing with that is that it's a PITA to work the sheetblock around all the hangar wires for the ceiling track frame.

Bryan

While we are on the subject of ceiling tiles, What are good ones to use without going with the fifty bucks and up kind?

Do you need 2x2 or 2x4? And how sturdy is the track? Do you want flush or recessed mount?

There are lots of options from standard commercial tiles (the solid ones with the holes in them) up to 6pcf fiberglass cores with MLV bonded to the back, to solid Melamine, to PEPP, etc.

Well, I am open to what might be the best option that is reasonable on the wallet. 2x4 panels are fine and flush would be cool too. Do you recommend any from the big box outlets?

At the big boxes, the best you'll likely find is the commercial ones. These are solid tiles that look like they're made from a compressed paper. They're solid and may or may not have holes in them.

Usually at those stores, the best you'll find may be 5/8" thick. Once you step up from there, you're looking at things that can go up to 2 1/8" thick and several sizes and weights in between.

Bryan

What do you think about using heavy mineral wool or compressed 'glass as your panels for a drop ceiling?

I was kicking around the idea of ripping the cheap vinyl tiles out of my drop ceiling and installing 4" thick mineral wool both attached to the floor joists above and used as paneling for the drop ceiling? Think it'll work for soundproofing, or is it just an enormous waste of money?

Just by holding a chunk of the 8lb rockwool over a loudspeaker one can hear abour how much sound the stuff absorbs/stops. It's a LOT. But the question is how do you get it to seal, air-tight, at the edges? Seems you'd be at least eliminating ceiling-floor standing waves all but entirely.

Good question Scott. Only prob is, giving up 4" below the floor joists is a lot of real estate. How would the 2" do? One could wrap them with a nice colored cloth for a unique and efficient ceiling?

Personally, I wouldn't use the mineral wool for the whole ceiling.

Any particular reason why,?

Well, I'd actually be giving up 8", but the existing drop ceilings are already 12" below the floor joists. For my application, it's more about soundproofing than acoustic correction.

1. Loss of isolation
2. Expense vs a decent drop ceiling with fluffy insulation
3. Too much broadband all on the ceiling leaving little room for more at other boundary ends.

Don't think you quite understood my previous plan.

26x14 room, joists 8 feet above floor, drop ceiling 6.5 feet above floor.

4 walls - all 4" rockwool. 3 of the 4 will be coupled to the exterior (concrete)

Ceiling - 2" rockwool panels to replace the existing cheapo glass panels.

Floor joists above - 4" rockwool coupled to the joists, with fluffy stuff between the joists.

Air space between ceiling and joists - approx 12 inches.