STC is an acronym used in acoustics. What does STC stand for?

• A. Sound Transmission Class
• B. Sound Absorption Coefficient
• C. Noise Reduction Coefficient
• D. Mass-Loaded Vinyl

Answer: (A)

STC stands for Sound Transmission Class. It’s the rating used to describe how well a partition—such as a wall, floor/ceiling assembly, or door—blocks airborne sound from passing from one side to the other. The concept measures how much sound is attenuated across a range of frequencies, and higher STC numbers mean better sound isolation. This is different from absorption, which deals with how much sound energy a surface takes in within a room rather than how much gets through the barrier. For example, Sound Absorption Coefficient relates to how a surface absorbs sound energy, while the Noise Reduction Coefficient is a single-number average of absorption. Mass-Loaded Vinyl is a material used to improve a barrier’s STC, but it isn’t what STC stands for. In practice, higher STC values indicate greater ability to keep sound from leaking between spaces, which is why they’re used in specifications for walls and partitions.