Transmission Loss analyses on fuselage panels: approach, numerical results and validation

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Transmission Loss analyses on fuselage panels: approach, numerical results and validation

Grooteman, F.P.

A new approach has been presented in detail to solve structural-acoustic problems. The structure as well as the fluid is modelled with the Finite Element Method. The new approach reduces the computational effort compared with a more conventional FEM approach. This is necessary in case of large models, existing for realistic aircraft structures such as fuselage panels or even a fuselage barrel, which are the structures analysed within the framework of FACE. The main objective here was to predict the sound transmission (TL) through these realistic aircraft fuselage panels. Results obtained with this approach are presented for a bare, damped (viscous constraining layer) and furnished (glass wool) large Aluminium fuselage panel configuration. The results have been compared with experimental data (modal and TL-data), validating the approach. For the Aluminium fuselage panel the correlation with the experimental transmission loss results is excellent for frequencies above the 350 Hz (less than 2 dB differences). Below the 350 Hz, a much higher TL is predicted in the numerical analyses. This can be due to errors in the calculated incident sound field, e.g. wrong value of the reflection coefficient. Similar results have been obtained for a Composite fuselage panel, although the correlation with experimental TL results was somewhat less than for the Aluminium panel, but still good for frequencies above the 400 Hz.