Interior building noise control research within the last few decades has engendered the creation of modern materials and material categories. Sound-damping gypsum wallboard has, since its introduction into the building construction industry, become a well-documented treatment for noise in buildings. Theoretical and experimental research has resulted in a fundamental understanding of constrained-layer damping (CLD) theory and of where it is most applicable. It has been discovered, for example, that sound-damping gypsum wallboard is an ideal treatment for speech privacy in enclosed spaces. Recent standardization of speech privacy for enclosed spaces has fostered discovery related to CLD applications. However, CLD research has also resulted in the realization that standards, building codes, and guidelines related to the Sound Transmission Class (STC) are in need of scrutinization and revision. Currently referenced sound transmission loss research reports and formal reports contain test data from a variety of labs over a relatively long period of time, from the early 1960s to the present time. A comparison of contemporary sound transmission loss data to earlier data results in contrasting STC ratings, often to the detriment of the tested assembly in regard to sound transmission loss. Similarly, when comparing contemporary sound transmission loss data for the same assembly partition but from various laboratories, there exists a large variation in the STC from laboratory to laboratory. These important issues will be discussed in detail along with solutions for cultivating progress in the building noise control industry.