Investigating flanking in mass timber construction: Acoustic performance of continuous timber panels over demising walls with resiliently isolated toppings

As mass timber construction gains in popularity and project design teams pursue optimized structural schemes and cost-effective designs, there has been a growing desire for Cross Laminated Timber (CLT) floor panels to maximize panel size. This offers structural benefits and constructability improvements, with fewer crane picks resulting in panels spanning across units. This has led to concerns and questions surrounding flanking sound transmission across a demising wall through the CLT panel to adjacent units. While ASTM E90 acoustic laboratory testing presents direct sound transmission measurements that does not include indirect transmission paths, the need for flanking measurements and field results for airborne sound transmission has become a major focus. To address this, the National Research Council of Canada (NRC) utilizes a four-room flanking facility that includes both direct and indirect transmission paths. In this study, measured Apparent Sound Transmission (ATL) and the subsequently calculated Apparent Sound Transmission Class (ASTC) results from the four-room flanking facility are compared with field measurements taken in a mass timber building. This study aims to compare the apparent transmission loss between room pairs with a resiliently isolated concrete and CLT panels continuously spanning across a demising wall.