Reduction in reverberation time, resulting from acoustic treatment behind the final surface layer of plywood or drywall

Abstract

When sound energy generated in room strikes a surface, it is partially reflected, partially transmitted, and partially absorbed. This is true for each layer of material in a wall, ceiling, or floor. The wave interaction with the surface depends on many factors, but the main factors that are typically involved in calculations of reverberation time are the frequencies of concern, the rigidity, and density of the surfaces, and the absorption of various objects in the room. For the case of an empty room, the estimation of the reverberation time is simplified down to the absorptive properties of the surfaces. This paper presents results that show the importance of considering the composition of the surface (wall, floor, or ceiling) including materials located behind the exposed surfaces. Specifically, it will be demonstrated that a properly installed layer of a loaded vinyl sheeting under the final wall surface layer of drywall will produce a significant reduction in the room reverberation time. With this technique, the preferred reverberation time can be achieved more naturally, while accommodating design constraints such as washable surfaces and minimizing the amount of additional surface treatments required. An additional benefit in the use of the loaded vinyl product behind the surface is a significant improvement in the STC of the wall or ceiling in which it was installed.