There is much controversy about whether using real egg cartons on the walls will soundproof a room. Garage bands with little money insist that this cheap form of soundproofing does make a difference. There is soundproofing egg carton foam that is made and can be purchased in sheets to insulate walls--this method is definitely more effective than using the actual cardboard egg cartons. It is also more costly. If you need to soundproof a room for little to no money, you might as well try the egg carton method yourself--it can't be worse than bare walls. Once installed, see if the resulting soundproofing is myth or fact. (Hint: ask your neighbours.)
Collect many, many egg cartons. Cardboard seems to be the most popular, although foam also works. It's the bubbly shape that helps scatter the sound waves and redirect them into the room.
Start in one corner. Open your egg carton.
Place it in the corner, with the bumpy side facing out. Staple the carton to the wall.
Align the next carton next to the first one. Staple the next carton in place. Continue in rows, until all walls are covered.
Have someone stand outside the room and see if the sound proofing has made a difference.
To help the egg cartons muffle the sounds, hang comforters, blankets or drapes against the walls. Foam is also a great sound absorber and works well.