Sound transmission class

Sound Transmission Class (or STC) is an integer rating of how well a building partition attenuates airborne sound. In the US, it is widely used to rate interior partitions, ceilings, floors, doors, windows and exterior wall configurations. Outside the US, the Sound Reduction Index (SRI) ISO index is used. The STC rating figure very roughly reflects the decibel reduction in noise that a partition can provide. To improve the sound transmission class and increase soundproofing two techniques are employed; sound isolation and sound absorption. Sound isolation entails blocking the path that sound can travel through by using cavity walls, adding resilient channels or using caulking to seal a room. Sound absorption entails adding extra mass to an already isolated partition, often using extra gypsum layers or by placing rockwool into cavities. Sound Transmission Class (or STC) is an integer rating of how well a building partition attenuates airborne sound. In the US, it is widely used to rate interior partitions, ceilings, floors, doors, windows and exterior wall configurations. Outside the US, the Sound Reduction Index (SRI) ISO index is used. The STC rating figure very roughly reflects the decibel reduction in noise that a partition can provide. To improve the sound transmission class and increase soundproofing two techniques are employed; sound isolation and sound absorption. Sound isolation entails blocking the path that sound can travel through by using cavity walls, adding resilient channels or using caulking to seal a room. Sound absorption entails adding extra mass to an already isolated partition, often using extra gypsum layers or by placing rockwool into cavities. The STC or sound transmission class is a single number method of rating how well wall partitions reduce sound transmission. The STC provides a standardized way to compare products such as doors and windows made by competing manufacturers. A higher number indicates better soundproofing than a lower number. The STC is a standardised theoretical measurement provided by ASTM E413 and E90 with the Field sound transmission class provided by ASTM E336-97 annex a1.