This proposal brings together specialists in aeroacoustics, aerodynamics and flight vehicle design to address directly this major gap in understanding aimed at enabling the design and development of efficient and quiet future multi-rotor propulsion systems. This proposal describes detailed flow and noise measurements in state-of-the-art facilities to gain a fundamental understanding into the aerodynamics and aeroacoustics of overlapping propeller systems. High fidelity flow and noise data will be used to establish new design principles and semi-analytical predictive models for high-efficiency low-noise multi-rotor configurations. In the final phase of the project the results from the project will be exploited to develop a full-scale low-noise multi-rotor demonstrator.