Article
Unmanned Aerial Vehicle for Bat Surveillance: Noise Emission of 5” Drivetrains (en)
* Presenting author
Abstract:
Monitoring bat populations in remote locations to collect data on species and population size is challenging. Unmanned aerial vehicles (UAV) allow for extensive coverage without the restrictions of monitoring bats with acoustic sensors mounted at fixed locations. The noise emitted by the UAV can either attract or deter bats. Our hypothesis is that some bats can hear the UAVs during observation. We investigated the sound pressure levels (SPL) at a defined distance up to 100 kHz of various drivetrains consisting of a 5” propeller (including toroidal), an electronic speed controller (ESC) and a brushless motor. The extracted data of our most suitable drivetrain was compared with the auditory brainstem response (ABR) data of 38 bat species to identify critical areas in the SPL spectrum to conclude on the acoustic surveillance capabilities of 5” propeller UAVs. We further extracted the drivetrain efficiency, as it determines the flight. Toroidal propellers eliminate SPL peaks by a considerable amount and produce less distortion for frequencies >3 kHz. We also found that different ESCs severely affect the SPL spectrum at high frequencies. ESCs with higher PWM frequency result in smoother frequency characteristics, especially at low thrust levels. Furthermore, we noticed a trade-off between low SPLs and drivetrain efficiency.