R-2.5HD Earthwool Sound Shield wall insulation offers high performance, with exceptional acoustic and energy saving properties, creating a peaceful environment in your home by absorbing sound and keeping it where it should be. Soundproofing is the process of developing acoustic treatments to supress, reflect, diffuse, or absorb sound waves. The best insulation for soundproofing is generally soft and porous materials, like cloth, as it is great at absorbing most sound. Other materials, such as metals, which are dense and hard, are impenetrable and reflect the sound. It fits snugly in a standard 90mm wall cavity and can also be installed in ceilings where the building is located beneath a flight path.