Aircraft interior noise prediction through Statistical Energy Analysis method

Aircraft fuselage structures are characterized by their lightweight design. The reduction of the mass of a structure is an important issue in the engineering field since it leads to reduced emissions and operating costs. On the other hand weight saving leads to an increase of vibration and noise transmission causing discomfort in the passengers. For this reason in the last years, the dynamic design of lightweight structures has received more emphasis such that it is done simultaneously with design process of the aircraft. In the dynamic behaviour of a structure, according to wavelength, there are two basic approaches: deterministic and stochastic. In the low frequency range the behaviour of a structure is deterministic and the basic tools applied for the analysis of vibration problems is finite element analysis on the numerical side and experimental modal analysis on the testing side. Model validation of finite element models for the low frequency range is mainly based on the correlation of eigenfrequencies and mode shapes from experiment and simulation. In the high frequency range, instead, the behaviour of a structure is stochastic which means that the dynamic response change strongly in case of small changes and uncertainty and statistics of system have to be taken in consideration. In the high frequency range, Statistical energy analysis (SEA) is widely used for the determination of vibration levels of the subsystems of structure. For correlation purposes in the higher frequency range, sound pressure levels and vibration levels are measured on pre-defined positions and are compared with simulated levels.