Predicting the sound transmission loss through finite-sized perforated brick walls using component mode synthesis

Bricks are often perforated to decrease weight, resulting in a decreased material cost and easier handling on site. However, walls made of perforated brick have a lower airborne sound insulation than solid walls with similar surface mass. This can be partially explained by thickness resonances and orthotropy. Sound insulation prediction models that include the detailed perforation geometry of all individual bricks are computationally demanding since a refined mesh is needed in order to properly capture this geometry. However, a brick wall typically consists of a repeating unit cell of three bricks and a mortar bond. In this paper, Component Mode Synthesis (CMS) is employed to eliminate the internal degrees of freedom of the unit cell to form a superelement. Based on these superelements, a quarter wall model is constructed and the diffuse sound transmission loss is computed within the hybrid deterministic-statistical energy analysis framework. The model is validated with experimental data obtained at the KU Leuven Laboratory of Acoustics. The computed results show a good correspondence with the data, while retaining a relatively low computation time.