Silastic for sealing a room

[boeing]

Hi,

I have recently constructed an "almost" room within a room. Basically I used 16mm MDF boards mounted approximately 3 inches from the existing walls and installed soundproofing sheets in the cavity (which I happened to score for free from a sound studio that just happened to be deconstructing a sound room that day - What Luck!!!). For the roof I fixed 16mm MDF boards to the existing beams and laid 80mm CSR (Australian Brand) Rockwool Soundscreen R2.5 batts in between the cavity of the floor above and the MDF boards (The soundproofed room is a basement type deal).
The batts block out about 80% of the sound in the room above which is great, but now I need to seal the room .

My question is what is the best type of sealant/silastic to use for sealing the gaps etc. I remember reading somewhere that Caulk is the best for soundproofing. Is this correct or is another type (ie. No More Gaps etc.) better?

Also, I know that egg cartons are useless in terms of soundproofing but are they any good for sound diffusing inside the room.
An egg company in Perth will sell me 12inch by 12 inch industrial size egg cartons, 98 of them for $21. Is it worth doing that as I am running out of funds for this project and this would only cost me about $140 to diffuse the whole room whereas the proper crap from the name brand places cost about $90 a roll which would end up costing about $500 for the room

Any help would be appreciated.

Regards,
Jimmy
Perth, Western Australia

[Hick]

Acoustical caulk is what you want.  It's different than draft sealing caulk- it will assure you that gaps will meet the same sound blocking as the material used for the panels. It will also remain flexible forever.  Metal tape should be used for the seams of your panels as well...

Re the egg cartons- count the cost of them, getting them and installing all them vs their effectiveness in your cost benefit anaylisis.

Hick