You can purchase egg crates (they are soft, foamy things you buy to make your bed more comfortable) in a bedding section of most department stores. They can cost anywhere from 10-50.00 apiece depending on where you get them. You can tack or nail these to your wall on the side(s) you wish to sound proof with the bumpy sides facing out. They aren't very attractive, but they will greatly reduce the sound.
You really can't do it for cheap, but you can drape blankets from the walls, and this will cut the sound transfer down. I have a buddy how spent more than I will say on here to sound proof his theater room.
sure you can- use egg cartons, newspaper and duct tape.
egg cartons and duct tape... You will need quite a bit
Thankies Loverlies Very Much