Within NRC concepts, how does gypsum wallboard (GWB) typically affect sound?

• A. Blocks sound and reflects it
• B. Absorbs most sound
• C. Conducts heat
• D. Is irrelevant to acoustics

Answer: (A)

Sound energy interacts with boundaries by transmission, reflection, and some absorption. Gypsum wallboard is dense and stiff, which makes it an effective barrier. Its mass resists vibration, so less energy gets transmitted through the wall to the other side. The energy that can’t pass is more likely to be reflected back toward the source than absorbed, especially since gypsum board itself isn’t highly porous and therefore doesn’t soak up much sound. In room acoustics terms, its impact on absorption (NRC) is small, but its role as a barrier that blocks sound and reflects energy is strong. That’s why this option is the best choice.