Dynamic characterization of the A400M acoustics fuselage demonstrator

Kurzfassung

Turboprop engines generate vibrations in the mid frequency range which are transmitted as structure-born sound to an aircraft fuselage. There it is radiated into the cabin as noise. To manage the acoustic impact validated simulation models and analysis methods are necessary. The A400M Acoustic Fuselage Demon- strator, a full scale aircraft fuselage, was used to develop test methods providing the validation data needed. The mid frequency range provides great challenges for such tests: To expand the well-established method of experimental modal analysis (EMA) into higher frequencies a very large number of measurement points is necessary. To ensure high quality results testing procedures from ground vibration tests (GVT) were adapted to the mid frequency range. The resulting sensor grid is a mixture of an optimized sensor distribution for low frequency analysis and a high density grid in the propeller plane of the A400M. To measure the approx- imately 2800 sensor positions a roving sensor method was used. Using several sensors permanently fixed to the structure the overall consistency of the data was analyzed. The methods presented here were able to provide high quality data used in later works for both model updating and method validation