Aeroacoustics Effects Generated by the Interaction Rotor-Airframe in a sUAS

Abstract

Small multirotor unmanned aerial systems (sUAS) have become more accessible and efficient recently, spurring their development for various personal and commercial uses. However, this rapid evolution raises concerns about security, control, and public health due to the proliferation of noisy drones. This study focuses on investigating a major noise source in drones called rotor-airframe interaction, which generates tonal noise through pressure fluctuations and wake interactions. To address this issue, we designed and tested three airframes with varying arm configurations. High-definition microphones and data acquisition systems were employed to measure pressure levels, and MATLAB code helped analyze the data as A-weighted signals to identify noise reduction possibilities. The key finding was that motor noise was a significant contributor, producing multiple pure tones at mid and high frequencies. Additionally, the noise signature was heavily influenced by the arm’s geometric shape and angles, underscoring the complex nature of rotor-airframe flow and acoustic interactions.