Replies

1. 
   DanH | Oct 29, 2006 04:53pm | #1

   Sound transmission is a strange thing. Sometimes you want stiffness, sometimes you want sponginess.

   Actually, the drywall scrap idea sounds pretty good. Especially if you lay the Liquid Nails on thick -- it'll help dampen vibrations. Go two or three layers deep if you have the patience. (When I worked for the Air Force we used alternating layers of foil and glue for vibration damping on flat panels. The drywall and LN would approximate this, plus add stiffness and mass.)

   Between wet cells and foam it's hard to say. The wet spray process removes some of the sponginess from the cells, which is probably not a good thing. Otherwise my gut feel would be cells.

   Seven blunders of the world that lead to violence: wealth without work, pleasure without conscience, knowledge without character, commerce without morality, science without humanity, worship without sacrifice, politics without principle. --Mahatma Gandhi
1. 
   ponytl | Oct 29, 2006 05:25pm | #2

   thanks... my gut tells me add as much mass as i can... and seal every hole and crack with caulk  or foam... everything i read says sound finds holes like water does on a flat roof and leaks the same way.... i have no problem have'n one guy spending a full day in one unit doing nothing but seal'n and caulk'n and glue'n scraps of drywall if... IF it gives results... i have also read that if you do double up drywall for sound use different thickness drywall  ie 5/8  & 1/2"  vs 2x 5/8" as the freq required to pass one is not the same as the freq to pass the other?

   thanks again for your input... this is something i have given a ton of thought to and read everything i can find on the net...  but still i have no clear cut path...

   hope things continue to improve for you

   p

1. 
   DanH | Oct 29, 2006 06:00pm | #3

   Yeah, one advantage of using scraps (that I hadn't though of until you mentioned the different thicknesses) is that the random sizes of scraps will not result in resonance like more uniform pieces would.Be sure that everything is well-attached, especially around the edges, so that there's no chance of rattling on a loose corner. (When in doubt, "caulk" the edge with LN.) And of course use LN when putting up the full sheets of drywall too.LN is a good substance to use here since it's "viscoelastic" -- it "flows" to a degree, which burns sound/vibration energy.

   Seven blunders of the world that lead to violence: wealth without work, pleasure without conscience, knowledge without character, commerce without morality, science without humanity, worship without sacrifice, politics without principle. --Mahatma Gandhi

2. 
   davidmeiland | Oct 29, 2006 08:34pm | #4

   I've done some sound wall stuff in recording studios and in a home where the wife did not want to hear the husband go pee-pee in the night. Gluing scrap rock to the inside of the wall won't hurt. Mass is good but it does relatively little to stop low frequency sound.

   Things I've done....

   hang a layer of 5/8", firetape and caulk everything, then hang another layer over the first using tons of adhesive. When the adhesive is dry, remove all the screws, which conduct sound waves thru to the framing.

   Or... hang a layer of 5/8, hang a layer of sound board, then hang another layer of 5/8. Sound waves have a harder time 'exciting' materials of different densities.

   Or... hang a layer of 5/8" from sound channel run across the studs.

   Hunt down sound isolating bushings for plumbing, if you have any in the walls. They are blue and orange rubber and work much better than the typical beige plastic bushings. Do not strap any pipe to the sides of studs.

   Hunt down clay sheets for the back of electrical boxes. I bought a case of it once and have since forgot what it's really called. It is soft claylike material about 1/8" thick and maybe 8 or 10 inches square. You mold it to the back of electrical boxes, sealing around the wires and generally adding mass.

   Now, the biggie, dollar-wise. From everything I have read, closed cell spray foam makes houses quiet. It ties things together quite well. You might consider that. You can buy DIY spray kits like Tigerfoam. Not cheap.

   I've had one or two occasions to have a sound consultant/engineer on the job. Their usual bread and butter is condo and apartment stuff. At least once I was handed some drawings of typical details, like wall sections. Maybe you can track down someone/something like that.

   The ball's loose, Seahawks recover, touchdown.

1. 
   ponytl | Oct 30, 2006 02:30am | #5

   thanks for the input... what i have already started doing is walking around with hilty foam and anywhere a pipe touches anything... i shim it out... spray foam around it and a few hours later remove the shim...  multi layers of anything are way out of the question money wise... I already have 2-3" of lightweight concrete over 3" of t&g decking between floors.... when i poured the concrete i put 2x sleepers/screed boards where each wall would be... so the concrete floor has speration between units and the hall... i had my electrican never put outlet boxes for side to side units in the same stud bay...  i have 4" of foam board on top of the roof decking... all walls go all the way upto the decking...

   I can buy a soy water based foam 20,000 board feet for $2K but the guy told me it's very hard to get just 1" coverage  try'n hard he said i might be able to keep it down to 3"....  which depending on how much someone charges me to spray it might still keep it under 10K...  which is still 10k more than i want to spend

   p

3. 
   sungod | Oct 30, 2006 06:20pm | #6

   I like solution "C". Just use fiberglas and foam insulation to keep the scraps from touching the interior drywall. Also drywall nails into the sides of the studs, not into drywall, will keep the scraps from falling out.