Comparison of the detailed and simplified methods to calculate the apparent sound transmission class for the proposed 2015 National Building Code of Canada

A new approach to the control of sound transmission is among the changes proposed in the 2015 edition of the National Building Code of Canada (NBCC). The design objective is changing from a minimum Sound Transmission Class (STC) for the wall or floor/ceiling assembly separating adjacent units to a requirement for the Apparent Sound Transmission Class (ASTC) which includes flanking sound transmission. One of the compliance paths in the proposed 2015 NBCC allows for detailed and simplified calculations according to ISO 15712. In support of the proposed 2015 NBCC, the National Research Council Canada has developed a number of guides for the calculation of the direct and flanking STC data for different construction types including concrete and concrete block walls with and without linings. As part of the development of the guides, it was found that the use of the simplified calculations could result in higher values for the direct and flanking STC values compared to the detailed calculations. The higher values put builders at risk of designs which have lower ASTC values than predicted. An alternative method for calculating the direct and flanking STC data for concrete block walls with linings has been proposed which is shown to reduce the risk of overestimating the direct and flanking STC data for the examples considered in this study.Peer reviewed: YesNRC publication: Ye