Transmission of impact sound in wood-framed construction

Abstract

Ongoing studies in the flanking transmission facilities at NRC-IRC have developed a framework for predicting the overall sound transmission, including flanking, in wood-framed multifamily buildings. Power flow via each flanking path is affected by five factors that determine a path transfer function specific to the type of excitation (airborne or impact) and the construction details. This paper examines how common construction details affect transmission of impact sound between adjacent rooms, which are either side-by-side or one above the other. Since the source room floor is an element common to all impact flanking paths, a series of toppings were evaluated as treatment options. Additional layers of gypsum board and improvement due to resilient mounting were evaluated for the walls in the receiving room. Estimates of the resulting impact SPL were obtained by summing the energy transmitted by the direct path through the floor assembly separating the pair of rooms (if applicable) and all the flanking paths involving the relevant wall-floor junctions. These estimates provide the basis for a design guide to predict sound isolation in typical wood-framed row housing or apartment buildings.