This Standard provides minimum requirements for rating masonry walls for sound transmission class (STC) and outdoor-indoor transmission class (OITC) based on testing calibrated calculation procedures. Topics covered include reference standards, definitions and notations, materials, construction, and methods to STC and OITC rating for concrete masonry and clay masonry assemblies. The Standard is written as a legal document in mandatory language so that it may form a part of a legally adopted building code. The Commentary presents background details, committee considerations, and research data used to develop the Standard. Separate equations for clay and concrete masonry walls are used to reflect the varying properties of these materials related to sound transmission. This standard is adopted by reference in the 2021 International Building Code.