Frequency modulation of an aerodynamic whistle-based bat deterrent

Abstract

The aerodynamic whistle-based bat deterrent by Zeng and Sharma 1, (“Aerodynamic-whistles-based ultrasonic tone generators for bat deterrence,” Physics of Fluids, 35, 2021) is numerically and experimentally analyzed for frequency modulation. Supply air pressure is modulated at various frequencies, amplitudes, and waveforms. At low frequencies (up to 100 Hz), the whistle exhibits quasi-steady behavior, and the radiated ultrasound follows the prescribed modulation. However, modulation at higher frequencies introduces multiple tones and distorts the modulation pattern. Measured farfield acoustic spectrograms reveal waveform skewness, likely due to nonlinear wave propagation in the conduit between the regulator and the whistle.