Calculating the Apparent Sound Insulation

The proposed National Building Code Canada 2015 (NBCC15) is set to replace the traditional design objective - the Sound Transmission Class (STC) - with a requirement including the effect of flanking transmission, namely the Apparent Sound Transmission Class (ASTC). The Code includes three paths for compliance with the new requirements, one of which is a prediction method.  The predictions differ for concrete and wood framed constructions, but for both cases, the predictions are based on European standards.   The National Research Council Canada (NRC) has written a number of guides which demonstrate how the calculations can be made based on measurements in the NRC’s flanking facility.   This paper discusses the details and the implementation of the calculation method as discussed in the NRC report, RR-331 “Guide to calculating airborne sound transmission in buildings.”