Aeroacoustics research in Europe: The CEAS-ASC report on 2019 highlights, Contribution: Perception-based evaluation of auralized future low-noise aircraft concepts

Abstract

To effectively reduce aircraft noise and its impacts on residents around airports, developments of low-noise strategies should consider the perception of sound. To that aim, a comprehensive simulation approach is pre-sented for the assessment and optimization of novel aircraft designs and flight procedures regarding perceived sound. The paper proves its feasibility by an application study on narrow-body twin-engine jet airliners. In this study, the effects of airframe modifications (e.g. landing gear mesh fairing, slat droop nose design, FOPP vortex generators), novel aircraft design, and tailored flight procedures on perceived annoyance are investigated. The key ingredient of the approach is the use of auralization for listening experiences of currently non-existing air vehicle flyovers in a virtual acoustic environment. First, aircraft and flight trajectories are designed. Second, spectral sound emission of each partial source along the flight trajectory is predicted using parametric models. Third, emission sounds are synthesized and propagated to ground-based observer locations with time-varying digital filters that simulate propagation effects such as Doppler effect, atmospheric absorption and turbulence-induced amplitude modulation. Multiple observer locations along the flight path are simulated to represent different expo-sure situations with varying noise source mixtures. The observer signals are spatialized for a hemi-spherical loudspeaker array. This allows listeners to experience the design parameters under varying operational conditions. With a psychoacoustic laboratory experiment, the changes in short-term noise annoyance to different low-noise technologies are measured. Significant annoyance reductions were found for the studied design parameters. Maximum benefit was achieved by the combined modification of the air vehicle and the flight procedure.