Based on the outcome of a workshop on aviation noise, this special issue on aircraft noise generation and assessment has been assembled. Invited contributions on preselected topics have been combined into one overall story line about both the aircraft noise generation and its assessment to provide an overview on the state-of-the-art capabilities in this research field (accounting both for modelling and measuring efforts). Although most relevant topics are covered, the editors do not claim that the collection of contributions is exhaustive for the multidisciplinary and vast research area dealing with aircraft noise. This issue is not restricted to current aircraft technology only, but includes low-noise technologies and novel aircraft design for subsonic and supersonic vehicles. Furthermore, an overview on measurement techniques, aeroacoustic windtunnel design, and low-noise modifications to existing windtunnels is provided. The selected paper contributions are all peer reviewed and display the status quo of experimental and numerical research activities in academia, at research institutes, and in industry.

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An innovative aircraft design of the Collaborative Research Centre (SFB) 880 features a new active high-lift system. This high-lift system is comprised of a droop-nose leading edge device and a Coanda flap as the trailing edge device. It offers very high lift coefficients and thus the ability to operate at airports that have reduced runway lengths, such as regional airports. Consequently, the assessment of aircraft noise is of utmost importance. The overall system noise on the ground is predicted using a parametric aircraft noise prediction tool. Although a parametric noise source model for the Coanda flap does not exist, it is estimated with a conventional Fowler flap model to evaluate the qualitative noise reduction potentials. The new design is compared with a regular aircraft that is equipped with a conventional high-lift system. Both designs are tested on individually calculated continuous decent approaches. The results show that airframe noise of the new aircraft is decreased due to later flap deflection and reduced speed. The engine noise, however, is significantly increased, especially on the glide slope. Hence, it dominates the overall noise on the ground, eliminating the benefits of the airframe noise reduction in the proximity of the airport. It is shown that the noise reduction potentials can only be exploited if the approach trajectory is individually optimized for low-noise.@en

I n October 2014, the first "Joint DLR & TU Delft Aviation Noise Workshop" was organized. This publication is the executive summary of this event. Overall, 38 invited participants f r om industry, academia, and research institutions have discussed the specific topic of this first 3 day workshop, i.e. "Aircraft Noise Reduction at the Source". The concept of the workshop was to avoid the usual presentation marathon but enable detailed discussions. The invited participants w i t h their various educational, cultural, and working backgrounds have been assigned into work groups to work on specific and predefined tasks. Four specific tasks were formulated i n order to address the problem, i.e. (1) identification of main aircraft noise sources on-board of a given reference vehicle, (2) assessment of simulation capabilities for noise prediction, (3) identification and assessment of promising noise reduction concepts for the reference vehicle, and (4) integration of these measures on-board of the reference vehicle. The major noise sources on-board of the reference vehicle as identified by the participants could have been reduced significantly i f selected measures are installed on-board. These proposed measures promise to reduce the system noise by 8 dB along a take-off and by 10 dB along an approach flight. Yet, the almost 65% reduction i n perceived noise as specified by ACARE's Flight Path 2050 could not be achieved. The most effective measure has been identified as structural shielding of engine noise emission. Overall, the workshop can be understood as the first attempt to estabhsh a new and active network for international cooperation i n the field of aircraft noise. @en