Determining recorder distances from multicopters to avoid bat disturbance

This study examines the impact of two multicopters, differing in size and weight (ConVecDro hexacopter, DJI Mavic 2 Pro quadcopter), on the activity of bats assigned to three distinct echolocation groups. The objective was to define thresholds (in decibels) below which bat echolocation groups show weak or no impact on activity. Using the known noise profile of the multicopter and a model of sound attenuation in air, these thresholds were then used to determine optimal microphone placement distances by estimating frequency-specific sound levels at increasing recording distances. Directional properties of the recording device were also considered.