Prediction and control of sound transmission through honeycomb sandwich panels for aircraft fuselage and train floors

Composite sandwich structures with honeycomb cores are increasingly considered as an alternative to aluminium for aircraft fuselages. Technical benefits include lower density, higher strength and greater fatigue resistance. The ability of composite materials to inexpensively be formed into complex shapes allows part count reductions and substantial cost savings. For railway carbodies, metal honeycomb sandwich panels are common in door panels and for interior floors. For floors the drivers are low weight, good moisture properties, fire resistance combined with high stiffness. Despite these advantages, sandwich structures may exhibit increased sound transmission compared to homogenous structures. Appropriate choice of core materials will reduce the need for subsequent noise control measures. In this paper it is shown how a physical understanding for the wave transmission phenomena together with modern prediction software, can be used to achieve designs that satisfy both acoustical and structural requirements. Calculated wavenumbers and transmission losses are compared to measurements for composite sandwich panels with honeycomb cores, treated and un-treated with damping layers. Modeling concepts as well as the potential for insertion losses due to added damping are discussed.