Active noise control in fuselage design

To achieve comfortable noise levels inside the passenger cabin, sound damping measures have to be taken to improve the sound insulation properties of the bare airframe. Usually the sound insulation requirements of a passenger cabin are met after the mechanical design of the fuselage structure is already finished, by adding damping materials. To be effective in the low frequency range, a lot of passive damping material has to be used resulting in considerable added weight. In this frequency range active noise control can be a competitive alternative to passive damping materials. To be able to find an optimal layout of an active noise control system a Design & Engineering Engine (DEE), a design support tool, has been developed. The DEE contains a parametric model initiator starting from user-defined requirements. From the parametric model an input file is generated for analysis with the FEM package ABAQUS. The DEE is capable of investigating active noise control systems comprising piezo electric sensors and actuators. Until now only parts of the fuselage section are investigated (panel level). The next step would be to analyse complete fuselage models. This research is mainly focussed on the influence of aspects like panel stiffness, panel curvature, stiffeners and the positioning of the sensors and actuators on the efficiency of the active noise control system. The efficiency of the active noise control system is expressed by the achieved transmission loss. The transmission loss for the different panel configurations is found using the transmission loss predicting algorithms developed at TNO TPD (Berkhoff [l]). These algorithms are based on transfer functions, which are the responses of the sensors to predefined input signals, and are determined with the DEE. Because the DEE can run automatically, many configurations can be investigated and the optimum layout for highest transmission loss can be found