Flanking impact sound transmission in wood‐framed multifamily construction

Abstract

This paper reports findings from a recently completed study of flanking sound transmission involving the wall/floor junction in wood‐framed multifamily buildings. Flanking transmission exists in all buildings, but it can be controlled through good design. The paper examines how common construction details affect flanking paths between horizontally, vertically, and diagonally separated rooms. Variables considered include mounting conditions and orientation of the floor joists, framing of the wall assembly and any associated fire blocking, and mounting and number of layers of gypsum board. Estimates of the apparent sound insulation were obtained by summing the energy transmitted by the direct path through the wall or floor assembly separating the pair of rooms, and all the flanking paths involving the relevant wall‐floor junctions. Results indicate that if there is no floor topping (i.e., the subfloor is bare) the apparent sound insulation for both airborne and impact sources is typically limited by flanking transmission involving the floor. Since, the source room floor is an element common to all impact flanking paths, three different toppings were evaluated as treatment options, and additional layers of gypsum board and resilient mounting were considered as options for the walls. The effectiveness of each option is discussed