what is STC rating
STC Rating. A commonly used measure of soundproofing effectiveness is the sound transmission class, or STC. It is a single number that attempts to characterize the overall ability of a material to reduce the transmission of noise.Any reputable product that is marketed as a good soundproofing material will include the STC in its product literature.t is a single number that attempts to characterize the overall ability of a material to reduce the transmission of noise. Any reputable product that is marketed as a good soundproofing material will include the STC in its product literature.