Cellulose insulation for traps

[Anthony]

As part of my "why don't you shut up, neighbor" project we are going to be blowing cellulose insulation inbetween the townhouses. It's actually a lot cheaper than I thought and we're not really doing the entire thing, just the bedroom, office, and possibly the theater. I have a half wall that resonates because like an idiot, I forgot to insulate it when I built it (I was just happy to have it done).

Anyway, we're probably going to have extra insulation and I was wondering if it would make a good trap, maybe encased in a frame, covered in muslin or burlap? It's probably not as heavy as rockwool, but it's apparently good enough to replace fiberglass bats in walls and attics.

Any thoughts on this?

[bpape]

Sure - you can use it. With the lighter density, you'll need to have extra thickness to compensate but less dense, thicker panels can still be very effective at lower frequencies. You could actually just build something like a coffee table and fill the underside with the insulation and wrap it in cloth but leave a nice wood top on it.

Bryan

[Anthony]

Question: would packing it in denser help, or is there a limit to this? I imagine at some point the insulation can't "friction absorb" and just starts to transmit through.

Sadly, I can't go to my neighbors house and set up a test. I would love to have a baseline 100 dB pink noise from his house before and after the insulation, extra drywall, and green glue all go up. Maybe he'll oblige by playing some death metal tonight and I can get an RTA reading

[MatrixDweller]

Are you using the spray in wet cellulose or the dry stuff? I've heard th dry stuff isn't worth anything for sound proofing. Sure it will fill in the void and have some effect, but you might not notice much of difference. Once you blow that stuff in you're not going to get it out without putting some big holes in the walls.

Blown in fiberglass would be much more effective, both from a heating & cooling and sound proofing nature.

Take a look at >> this stuff <<. It might be worth investigating if you're trying to squeeze every single last STC point out of your wall. Check out the rest of the site too. There's a lot of info about sound proofing there.