Theres decent stuff like those big black rolls of sound proof stuff that are like a couple hundred a roll.It would hardly cost $10,000 to reduce audio leaking substantially considering the area isnt large.Yes egg cartons do nothing to block sound.Ive heard that they can actually enhance certain frequencies.

If your looking to stop bouncing soundwaves and other space/sound issues...then you might be looking toward 1500-2000 tamales for that kind of sha-bang.
Wow I'm full of lousy vocabulary tonight!

Later! \m/