Soundproofing has two components: reducing noise and absorbing noise.
Reducing noise means stopping it from getting into or out of a room in the first place by using space, or creating distance between the sound source and the listener. Using mass, or barriers of thick material, also reduces noise. Absorbing noise means reducing the amount of vibration, echo and sound reflection. Homes and businesses can use these methods to reduce unwanted noise from outside sources.
Barrier Methods of Noise Reduction
Thick, solid walls will eliminate more noise than thinner, hollow ones will. Noise will drop as sound moves through layers with different densities, such as moving through an exterior wall and then an interior plaster wall.
Absorbing Sound in the Home
Thick draperies help contain noise within a room. Upholstered furniture and dense carpet also absorb sounds. Anything made from soft fabric dampens sound while hard or shiny surfaces reflect sound. Removing mirrors, draping walls and windows with heavy material, and covering flat surfaces with fabric will help soundproof a room. Double-paned windows reduce noise because the sound has to travel through both layers of glass as well as the air space in between.
Absorbing Sound in Commercial Buildings
Theatres and concert halls use soundproofing materials to control the quality of sound within the performance space and to limit outside noise coming in. The buildings may be constructed so the sheetrock and insulation have maximum sound-absorbing capability. Performance venues and recording studios install acoustic ceiling tiles and acoustic wall foam resembling egg cartons to reduce sound transfer.