Calculating the Apparent Sound Insulation in Cross Laminated Timber Buildings

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). Such a transition requires a supporting set of technical standards for measuring direct and flanking sound transmission for typical assemblies and junctions, plus a credible procedure for calculating system performance from these inputs. As part of this change, the National Research Council Canada has written a guide and construction specific research reports to calculate the ASTC of concrete, concrete block, steel frame, wood frame and cross-laminated timber (CLT) buildings. This paper discusses the calculation method and examples that are contained in the National Research Council Canada’s report RR-335 “Apparent Sound Insulation in Cross Laminated Timber Buildings”.