What do the letters STC represent in sound-blocking efficiency ratings?

STC stands for Sound Transmission Class, which is a rating used to measure the effectiveness of a building material or assembly in blocking sound. The STC rating is primarily applied in construction to evaluate how well walls, floors, ceilings, and doors can reduce sound transmission from one space to another. A higher STC rating indicates better sound insulation properties, making it a valuable metric for architects, builders, and homeowners interested in noise control within different areas of a building.

The other terms listed do not accurately represent the established metrics used in soundproofing. Each of those options, while they may sound relevant, does not have recognized definitions or applications in the context of sound insulation. Thus, the correct identification of STC as Sound Transmission Class provides clarity on its specific function in assessing sound-blocking efficiency.