Contributions of Different Aeroacoustic Sources to Aircraft Cabin Noise

Abstract

The turbulent boundary layer (TBL) on the fuselage, jet noise and the air conditioning system (ACS) are considered as three important aeroacoustic sources of aircraft cabin noise. To improve current cabin noise prediction approaches as well as to investigate the different noise sources and their respective noise transfer paths, flight tests with DLR’s A320-232 research aircraft ’D-ATRA’ were carried out within the German national (LuFo IV) project SIMKAB. Extensive measurement data were collected using microphones inside the cabin, unsteady surface-pressure sensors for the characterization of the external TBL- and jet noise induced fuselage excitation, and accelerometers mounted at the frame structure, fuselage skin fields and cabin panels. Flight speed and -level as well as engine and air conditioning system operating conditions were varied to separately evaluate their parametric effects on cabin noise. The analysis of this extensive data base is still ongoing; in the current paper the focus is set on the results from microphone measurements at various longitudinal positions inside the cabin. Both TBL- and jet noise induced contributions increase towards the rear, reflecting the natural growth of the TBL thickness and typical jet noise radiation characteristics. Contrary to that the air conditioning system noise is of minor importance.