The bottom portion of egg cartons with the open cell placed against the wall helps to soundproof a room. Air is a wonderful soundproofing agent, and the little cells in the egg cartons provide thousands of air pockets to buffer noise. A vacuum is formed when you glue the egg cartons to the wall, helping to absorb noise. Remove the top portion of the egg carton and glue the lower half on the walls you wish to soundproof. Keep them close together one after the next to form an interesting pattern with lot of texture. After mounting the cartons, paint them with interior latex paint. Using a paint sprayer is the best way to accomplish this task. Spray on several thin coats to prevent the paint from running.
Cork on the walls helps to deaden noise. Cork has tiny air pockets that help trap noise and prevent echoing. Many recording studios use cork on their walls to help reduce noise and echo. Cork comes in a variety of sizes and weights and is easy to apply. Cork tiles can be glued to the wall to form a solid surface. If you use cork tiles in an office or child's room, it can double as a bulletin board or a place to pin up posters, paintings and children's artwork.
Indigenous cultures have been using rugs not only to create wall divisions in tents and large rooms, but also as soundproofing. This is a wonderful way to add some new decor to your room and a great excuse to go shopping. Check out antique auctions for great buys on stunning antique and vintage oriental-style rugs. Alternatively, you might enjoy using contemporary rugs or carpet squares attached to your walls to help deaden noise.
Energy-absorbing foam blocks may be helpful in absorbing noise from stereo speakers. If you use these blocks to help absorb base waves from your stereo, place them on inside walls or in the middle of a room on the floor rather than against the outside or conjoining walls with neighboring apartments.
Like cork, Styrofoam panels have energy-absorbing abilities and can help to deaden noise. These work well when glued to the walls one next to the other to form a layer. Styrofoam walls make great places to pin artwork, notes, homework or posters; however, once you've indented the Styrofoam, it won't return to its original shape.