Auralisation and assessment of time-varying characteristics of Unmanned Aircraft System noise

Noise is one of the key barriers for the deployment of Unmanned Aircraft Systems (UAS). Compared to conventional aircraft and rotorcraft, UAS operates closer to communities and produce a noise signature with more tonal and high frequency noise. Other important characteristic of UAS is the unsteadiness of the noise signal produced due to the influence of weather conditions. Wind gusts dynamically alter UAS aerodynamic and propulsion characteristics, causing rapid changes in rotors' rotational speed and fluctuations in rotor loading. These dynamic changes in amplitude and spectral content of tonal and broadband noise can lead to high noise annoyance. This paper presents an overview of a modelling framework able to account for time-varying characteristics of UAS noise under realistic operating conditions. Preliminary results of a listening experiment are described, suggesting the importance of amplitude modulation depth, modulation frequency and time-varying modulation profiles on UAS noise annoyance. These findings highlight the need for embedding these acoustic criteria into the optimisation for UAS flight control to minimise community noise annoyance.