A framework to simulate and to auralize the sound emitted by aircraft engines

Abstract

In civil aviation, the well-established Effective Perceived Noise Level (EPNL) has remained, so far, a simple but reliable psycho-acoustic metric, representing the backbone of noise regulation politics and leading to quieter aircraft turbofan engines. However, the recent changes induced by further acoustic optimization of engines, or the introduction of innovative designs, suggest that a more refined assessment than the sole EPNL metric is needed, which is based on sound auralization. The paper presents a framework of simulation tools that are currently being developed at the DLR Engine Acoustics Department with the goal of assessing novel designs at a very early development stage. This framework allows to simulate acoustically an engine flyover and to produce audible signals as perceived by a virtual observer standing on the ground. The source calculation is performed by the tool PropNoise and relies on analytical physics-based models for the fan noise sources, and Stone's semi-empirical jet noise model. The subsequent tool VIOLIN simulates the propagation of sound through the atmosphere and the ground reflection effects. Finally, the spectrograms of the broadband and tonal noise components are converted to audible sound by the auralization tool CORAL. The procedure is applied to a realistic engine test case and compared with experimentally recorded sound.