The forced sound transmission of finite ribbed plates, investigating the influence of point connections and periodicity

Many engineering structures consist of plates being stiffened by ribs. The ribs can be connected to the plate in a line connection (welded or glued) or in point connections (screwed). It is well known that the rib stiffeners can significantly change the vibration field and the radiation behavior of the structure. These types of structures have thus often been studied in the past. However, there is still a lack of simplified expressions for the sound transmission of these structures. Therefore, simplified expressions for the forced airborne sound transmission of finite size single leaf ribbed plates have been derived, using a variational technique based on integral-differential equations of the fluid loaded plate. In this way an optimal solution is derived, using a very simple initial guess of the vibration field. The finite plate is assumed being mounted in a rigid baffle. The approach is based on the theory derived for a non-stiffened single finite plate [J. Brunskog, JASA 132, 1482-1493, 2012]. Basic results for the ribbed plate have previously been reported, but with a poor fit to measured data. In this paper, this approach is investigated further, trying to explain the previous misfit and improve the model. The influence of point versus line connections, as well as periodicity effects, is investigated.