Is styrofoam good for soundproofing?

Diy doc is correct about the egg cartons. I play drums and tried everything to do what you call "sound-proof" One success I had was with dense styro foam ...this foam is actually compressed from very thick sheets to smaller ones. With the compression, the R value is very very high!! I got all of mine for free by going to a buss. that installs room enclosures....a company called HORIZON is a big one. I just picked scrap for about 2 weeks from the back. I hope this helps.