Sound radiation efficiency measurements on cross-laminated timber plates

Cross-laminated timber is an engineered wood, constituted by an odd number of layers of lumber beams glued together orthogonally. CLT is gaining popularity in Europe and North America, both for residential and non-residential buildings, as it represents a valuable alternative to traditional construction materials; however, it does not provide sufficient sound insulation due to the low surface mass combined with the high stiffness. The sound radiation efficiency is a fundamental parameter to describe the coupling between structural waves propagating in a vibrating element and the sound waves in the adjoin fluid and it is proportional to the ratio between the radiated sound power and the mean square velocity of the surface. Currently there is no standard procedure available to measure radiation efficiency, neither in laboratory nor in-situ. A complete vibro-acoustic analysis on three CLT plates under different excitation cases has been performed. Two measurement techniques to evaluate the surface vibration velocity and various approaches to compute the sound radiation efficiency have been analysed and compared. The methods and principal results are presented and discussed in this paper.