Home recording is a huge industry - as consumer technology has caught up to professional industry standards, more and more musicians and artists have eschewed the popular recording studios in favor of recording in their basement, garage, or bedroom. One of the last hurdles these artists face, however, is that of soundproofing.
Effective soundproofing for a home studio environment can be effective and cheap - if one knows how to go about it.
Sound Proofing vs. Sound Reduction
One of the many solutions to this issue is somewhat of a misnomer. Sound reduction is not reducing the sound "bled" through the walls, but rather reducing the sound that is generated in the first place. This can take many forms, and often has a negligible result on your finished product.
Drummers can apply what is known as "drum triggers" to their kit after silencing their drum heads, allowing for triggering of samples in their recording device of choices. Guitar amplifiers can be emulated via a PC, skipping the mic'd amp process entirely. Singers can record their pieces using long wires reaching to a bathroom, as these often boast great sonic qualities while maintaining a level of isolation.
By reducing the amount of sound generated, your needs for sound proofing are diminished. For those that choose to mic their amps for a warmer sound or record live drums for a better room sound, proofing is the best choice.
Egg cartons are an age old sonic reduction product. Because of the unique geometry of the cartons, sound is captured rather well, and instead of being absorbed and reflected as they would with a regular wall, they are reflected in a scattered pattern, reducing the overall noise that is bled through the wall.
Apply the egg cartons using double sided tape or velcro, and you can avoid damaging your wall long-term. For a more permanent solution, egg carton-shaped materials are produced professionally by various sound design companies at a heavily marked up price.
Carpets and Remnants
Carpets and remnants, which are functionally just pieces cut off carpets to match size orders, are a great muffling material. Piled up in the low corners of the room, they absorb a lot of the echo that sound in a closed space generates. Even better, if they can be hung from the wall (either using heavy duty mounting brackets or closet hanging-rod fixtures), they can severely reduce the amount of sound that is bled through.
While carpets can be expensive, remnants are often considered "waste" by carpet manufacturers, and can be picked up marked off by as much as 90% the original price! To learn more, visit Poll Sound.