Effects of Static Load & Parasitic Airborne Sound on Kij Measurements

The construction sector is increasingly adopting more sustainable materials, with engineered timber products such as cross‑laminated timber (CLT) gaining popularity due to their low carbon footprint, light weight, and high strength‑to‑stiffness ratio. 

However, their intrinsically poor acoustic performance remains a key challenge, particularly regarding flanking sound transmission across wall and floor junctions. Mitigation measures such as resilient strips can improve performance, but their effectiveness strongly depends on the junction type. Flanking attenuation is quantified by the vibration reduction index, K_ij, measured according to ISO 10848. 

This study presents results from laboratory testing on a CLT horizontal X‑junction, identifying key factors affecting the reproducibility of K_ij measurements. These include parasitic airborne sound transmission, which can lead to underestimated K_ij values, and the influence of static loads compressing the junction, increasing rigidity and altering the behaviour of resilient elements - conditions representative of load‑bearing structures in real buildings.