Mass-loaded vinyl is described as which of the following?

• A. Lightweight fiberglass insulation
• B. Dense, flexible material that blocks sound at walls, ceilings, between studs, or as flooring underlayment
• C. Sound Absorption Coefficient
• D. Noise Reduction Coefficient

Answer: (B)

Mass-loaded vinyl works by adding mass to a boundary to block sound transmission. It is a dense, flexible sheet designed to act as a barrier, so it can be used behind drywall, between studs, on ceilings, or as a flooring underlayment to increase the assembly’s sound-blocking capability. This uses the mass law principle—more mass equal more sound reduction—so it’s effective at reducing noise passing through walls and floors.

This isn’t lightweight fiberglass insulation, which is mainly for thermal insulation and some in-room absorption rather than forming a high-mass barrier. And the other options aren’t materials or products but measurement terms: sound absorption coefficient and noise reduction coefficient describe how a material absorbs sound in a room, not how it blocks sound transmission through assemblies.