Psychoacoustic optimisation of aircraft noise - challenges and limits

With regard to the reduction of noise emitted by aircraft, there are approaches to reduce both the source power itself and the shielding of certain sound sources towards the ground. As dominant partial sound sources, countermeasures to jet and fan noise are particularly in focus. In this work, the impact of two promising approaches - chevron nozzles and the engine-over-the-wing (EoW) concept - are evaluated concerning their psychoacoustic relevance on audibility by means of auralizations. Therefore, a comparative study of the sound radiation of normal and chevron nozzles based on the results of fluid dynamic simulated (CFD) jet flow is presented first. For the evaluation of the acoustic jet noise properties it is shown to necessarily consider standard-conforming sound power calculations as well as to analyze the full-spherical directivity including its frequency dependence. Secondly, the effects of fan noise shielding in the EoW concept are simulated in a landing scenario. Therefore, the sound field for di erent receiver positions is calculated considering the atmospheric sound propagation and evaluated under consideration of psychoacoustic aspects.