Beating effects in multirotor electric aircraft noise

Document Type

Conference Proceeding

Publication Date

1-1-2026

Abstract

The sound quality metric of fluctuation strength has been shown to be potentially important in psychoacoustic studies of unmanned aerial vehicles (UAVs), despite this metric capturing perception of modulation frequencies much lower than typical UAV blade passage frequencies (BPFs). This paper demonstrates how beats generate low frequency modulation in UAV noise measurements: even when rotors were set to the same BPF setpoint, beats were generated by small BPF variations, which followed Gaussian distributions. Beats have been studied in the literature for 2 tones, but not 3 or more tones, which are representative of the tonal noise generated by multirotor electric aircraft. Beats of more than 2 tones were characterized by the BPF differences between all rotor pair combinations. The BPF distribution and noise generated by a single rotor were used as inputs into the developed noise prediction methodology to predict the probability distributions of beat frequencies and SPL modulation amplitudes. The predictions showed good agreement with noise measurements of 2 and 6 rotors, where beats were significantly audible with fluctuation strength > 0.1 vacils.

Publication Title

Proceedings of Meetings on Acoustics

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