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.
Vibro-Acoustical Sensitivities of Stiffened Aircraft Structures Due to Attached Mass-Spring-Dampers with Uncertain Parameters
The slightest manufacturing tolerances and variances of material properties can indeed have a significant impact on structural modes. An unintentional shift of eigenfrequencies towards dominant excitation frequencies may lead to increased vibration amplitudes of the structure resulting in radiated noise, e.g., reducing passenger comfort inside an aircraft’s cabin. This paper focuses on so-called non-structural masses of an aircraft, also known as the secondary structure that are attached to the primary structure via clips, brackets, and shock mounts and constitute a significant part of the overall mass of an aircraft’s structure. Using the example of a simplified fuselage panel, the vibro-acoustical consequences of parameter uncertainties in linking elements are studied. Here, the fuzzy arithmetic provides a suitable framework to describe uncertainties, create combination matrices, and evaluate the simulation results regarding target quantities and the impact of each parameter on the overall system response. To assess the vibrations of the fuzzy structure and by taking into account the excitation spectra of engine noise, modal and frequency response analyses are conducted.
Dynamic characterization of the A400M acoustics fuselage demonstrator
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