Acoustic labor in Ottobrunn. The compliance with noise regulations at airports is a very critical issue for aerospace industry. The launch of turbofan engines with a high bypass ratio reduce significantly the overall perceived noise level of commercial aircraft. EADS-CRC investigates the physics of the noise generating process of the tonal fan and develops new active, passive and adaptive concepts to meet the demands of the future. These concepts comprise multi channel Active Noise Control, multi degree of freedom liners and new resonator strategies.
ARIANE-5 upper-stage injection system Modal analysis of the ARIANE-V upper-stage injection system. Highly dynymic and which stability may easily be influenced by the dynamic behavior of the propellants during the sensitive reaction phase, the combustion process behavior is strongly characterized by the injector system. EADS-CRC investigates the structural dynamics of the injector system by doing a modal analyses on the hardware. Results are modal parameter such as eigenfrequencies, damping, and mode of vibration and structural impedances. These parameter will be used in order to avoid dangerous structure-fluid coupling effects.
Prototype active trim panel has piezo-ceramic actuators embedded in its inner honeycomb layer. They will be fully enclosed and invisible when the panels are installed. Noise levels inside modern aircraft are relatively low because engines, the main source of external noise in flight, have become much quieter and the insulation and sound proofing materials in the cabin wall generally work quite well in damping noise. There is, however, still room for improvement. The distinct frequency peaks of the whirring noise coming from the engine fans during take-off and climb can still be annoying and the broadband noise from the engines exhaust and from the air streaming along the skin of the aircraft causes unpleasant sound levels during cruise. Noise from the outside is transmitted as vibrations through the cabin structure, which consists mainly of the outer skin and frames, a glass wool thermal insulation layer and the trim panels. These plastic linings radiate the sound waves into the cabin. While noise in the frequency range above 500 Hz is damped quite well, adding more sound proofing material to prevent the low-frequency buzzing and broadband noises from reaching the passengers is not a viable option, because too much weight and bulk would be required. This research is being carried out as part of the Friendly Aircraft Cabin Environment (FACE) project within the European Union`s 5th Framework Programme.
Noise reduction tests on active suspension elements
Prototype active suspension elements will be mounted between a section of carbon-fibre composite fuselage structure and a trim panel for noise reduction tests. Specimens were fitted to a generic fuselage section in a window between the reverberation room (representing the outside), where powerful loudspeakers emit specific noise frequencies, and the anechoic room (representing the cabin side), where the remaining noise transmitted through the test panels was measured with an intensity probe. The effectiveness of reducing noise transmission by active panels and suspensions was so assessed, with both concepts providing good results. Reductions in radiated sound power of up to 20 dB (down to 1%) for discrete frequencies and 10 dB (down to 10%) for broadband noises were measured. Advancing from the proof-of-concept stage, researchers are presently in the process of assembling larger wall structure test sections made of carbon-fibre composites. Still within the FACE project, active suspension elements as well as curved active trim panels are going to be tested in the acoustics laboratory.
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EADS Deutschland GmbH · 81663 Munich · Germany EADS France S.A.S. · 37, boulevard de Montmorency · 75781 Paris Cedex 16 · France EADS CASA · Ava. de Aragón, 404, 28022 Madrid · Spain
