Numerical and experimental studies on impact sound radiated by rib-stiffened plates

Rib-stiffened plates are widely applied in civil engineering as they achieve a similar static stiffness as plain plates with a substantially lower weight. Unfortunately, this generally leads to a reduced impact sound insulation. The quantitative assessment of the impact sound insulation of rib-stiffened plates is complex for most of the acoustic frequency range. At the frequencies where the wavelength of deformation is much larger than the stiffener spacing, the stiffeners induced orthotropy leads to an increased width of the coincidence zone. At high frequencies, the point impedance is much larger at the ribs than in between them. This work aims at gaining insight in the impact sound radiation performance of rib-stiffened plates. To this end, a dedicated impact sound computation model is proposed. A finite element model of a rib-stiffened PMMA plate is constructed, in which the mechanical properties are calibrated using experimentally obtained modal characteristics. This model is coupled to a diffuse model of an adjacent room, and the predicted impact sound radiation is validated by measurements. Finally, the effect of adding stiffeners is numerically investigated by comparing the sound radiation efficiency, vibration level, and impact sound radiation of the rib-stiffened plate and simulated plane PMMA plates with equivalent static stiffnesses.