Sound Insulation is using certain materials to reduce the sound pressure with respect to a specified sound source and receptor (noise control). There are several basic approaches to reducing sound: increasing the distance between source and receiver, using noise barriers to block or absorb the energy of the sound waves, using damping structures such as sound baffles, or using active antinoise sound generators.
Sound Insulation affects sound in two different ways: noise reduction and noise absorption. Noise reduction simply blocks the passage of sound waves through the use of distance and intervening objects in the sound path. Noise absorption operates by transforming the sound wave. Noise absorption involves suppressing echoes, reverberation, resonance and reflection. The damping characteristics of the materials it is made out of are important in noise absorption. The wetness or moisture level in a medium can also reflect sound waves, significantly reducing and distorting the sound traveling through it, making moisture an important factor in sound insulation.
Residential sound insulation aims to decrease or eliminate the effects of exterior noise. The main focus of residential soundproofing in existing structures is the windows. Curtains can be used to damp sound either through use of heavy materials or through the use of air chambers known as honeycombs. Single-, double- and triple-honeycomb designs achieve relatively greater degrees of sound damping. The primary sound insulation limit of curtains is the lack of a seal at the edge of the curtain. Double-pane windows achieve somewhat greater sound damping than single-pane windows. Significant noise reduction can be achieved by installing a second interior window. In this case the exterior window remains in place while a slider or hung window is installed within the same wall openings.