181 / 2021-03-31 19:03:54

Identification and assessment of flanking transmission in measurement of sound transmission loss of multilayer panels

Sound transmission loss,Vibration transmission,Wave propagation,Diagnostics,Transfer path analysis

Vibro-acoustics and Structure-borne Noise

The sound transmission loss measurements of small-sized panels ideally require perfect sealing of the panel frame and a rigid construction of the filler wall that encloses the panels. In practice, suppression of flanking transmission is achieved by having a sufficient isolation between the source and the receiver rooms and blocking the indirect transmission path by installing additional elements on the surfaces of both rooms. At the outer edges of the panel, the frame is supported by acoustically reflective materials and insulations to dampen the energy propagated into the wall. The sound transmission loss of the panels can be improved by installing additional layers that contribute to more efficient dissipation. These layers are installed such that they sit tight in the frame with bolted connections and a niche is introduced on the sides and at the top to further secure the panel within the opening. However, for panels with alternating layers of solid and porous materials, and acoustic cavities, the structural rigidity of the supporting frame and joints are the primary factors that contribute to flanking transmission. In this study, we investigate the extent of this transmission, and identify the vibration transmission paths and assess their negligibility in measurement of the sound transmission loss of the multilayer panels. A source-path-receiver approach has been proposed for ranking the critical transmission paths for different panel configurations. For this purpose, an experimental setup comprising transducers were used to measure the acoustic response of the room and vibration response of the structural elements at operating conditions. A finite element model in COMSOL is set to validate the results and compared with an analytical solution.