From engine integration to cabin noise: drivers to accurate interior noise evaluations
The present paper addresses the topic of of end-to-end cabin noise aero-vibro-acoustic prediction for civil aircraft. Through an overview of Airbus cabin noise prediction means and related investigations, the sensitivity of cabin noise to key parameters at engine and aircraft levels is demonstrated, highlighting the need for high fidelity numerical and experimental capabilities as well as integrated ways of working between engine and aircraft manufactureres in the frame of engine design to cabin noise.
Design Requirements of Acoustic Flight LAB Platform
Economic aircraft design demands for short development times. In frame of interior noise this requires reliable prediction methods for the design process, where the complex interaction of the excitation/fuselage as well as the radiation to the cabin is captured. Especially in the mid frequency range between 80-250Hz modern finite element based numerical models still show a lack of accuracy for a full aircraft configuration. However it is difficult to find out which part of the model has the highest impact on accuracy. Flight tests/ground tests of full aircraft configurations have an inherent high complexity and only a limited observability. Therefore in frame of the Lufo-4 funded project COCLEA an acoustic design platform is developed to serve as basis to improve numerical models by stepwise increase of the complexity. The main design requirements are: realistic excitation, fuselage structure with low complexity and clean boundary conditions. In this paper the importance of these requirements are demonstrated by results from an existing platform (A400M Fuselage Demonstrator). Here the limits due to high complexity and boundary conditions are shown by comparison of numerical model with detailed test data. Furthermore first results of the excitation reproduction system consisting out of 128 speaker array are presented.
Experimental characterization of vibro-acoustic properties of an aircraft fuselage
Modern turbo-prop engines have been identified as an efficient alternative to jet engines for the propulsion of next generation short range aircraft. However, the benefit in operating efficiency comes along with disadvantages related to engine noise and noise transmission into the aircraft cabin. 
Numerical models used for response analysis often show significant deviations in the medium frequency range up to 500 Hz. Model validation based on experimental modal data is often not possible due to the high modal density that aircraft fuselage structures exhibit in this frequency range. 
A method is presented that provides a meaningful correlation of the results of vibration tests on aircraft fuselage structures with corresponding numerical predictions. The correlation criterion used is inspired by statistical energy analysis and is based on kinetic energies integrated over frequency bands and spatially integrated over surface areas of the fuselage structure. The objective is to indicate frequency bands where the finite element model needs to be adjusted to better match with experimental observations up to 500 Hz and to locate the areas where these adjustments should be applied. 
The application of the kinetic energy correlation criterion comes along with several requirements on the test equipment, test installation and testing procedures. An effort has been spent to extent well defined testing procedures stemming from aircraft ground vibration testing into the medium frequency range. As a result, a test method is presented that has been applied in a test campaign on a full-scale aircraft fuselage structure to validate the proposed correlation criterion based on kinetic energies.