Investigating flanking noise transmission in mass timber construction through laboratory measurements of isolated floor toppings

Mass timber is quickly becoming a popular design choice for multifamily residential development, with recent changes to building code allowing high-rise mass timber and the push towards lower embodied carbon or net zero construction. Cross Laminated Timber floor panel layouts and structural grids often result in continuous panels spanning between units or require rigid connections between panels, thus flanking noise transmission between units is an especially important acoustical design consideration. Quantifying the flanking noise transmission performance of a junction in an acoustical assembly requires knowledge of the vibration attenuation characteristics of its elements. The vibration reduction index (Kij) measures the transmission loss of a junctions' flanking paths by quantifying the transmission of vibrational power through its structural elements. This study utilizes Canada's National Research Council's four-room flanking facility to measure the Kij of flanking paths through a CLT wall/floor junction with and without isolated floor toppings on a resilient interlayer. Apparent Sound Transmission Class (ASTC) is then calculated from the measured Kij. The analysis presented investigates flanking noise transmission of a floating floor on a Cross Laminated Timber Panel spanning between the four rooms, with additional research into the effect of adding bulkheads on the ceiling side of the junction.