What is an STC and/or an IIC rating?
STC stands for sound transmission class. It is defined as an integer-number rating of how well a building element reduces airborne sound. It is a calculation based on transmission loss values through an element. Transmission loss is the measurement of the noise reduction in individual frequency bands from a source room containing noise to a receiving room containing a microphone. The transmission loss values are also corrected for room absorption on the receiving side. IIC stands for Impact Insulation Class. It is defined as a single number rating derived from the normalized impact sound pressure levels through a floor ceiling assembly. The sound source is a standard tapping machine through which sound pressure levels radiate off the bottom of the assembly into a receiving room and are then normalized for the rating calculation. There are nearly unlimited systems this testing can be performed on. Intertek offers three standard systems and can build nearly any system requested.
