Bats live in groups of tens to hundreds in dark caves, where numerous ultrasonic signals can cause acoustic interference. Previous studies have reported frequency-adjusting behavior in bats, in which they modulate the terminal frequency (TF) of their frequency-modulated (FM) pulses during flight to mitigate interference. However, the effectiveness of this behavior in avoiding acoustic interference remains unconfirmed. To investigate this, we developed an ultrasound-sensing autonomous vehicle with a one-transmitter, two-receiver configuration, mimicking bat echolocation. The vehicle employs cross-correlation processing of transmitted signals and echoes for object localization and navigation. A mathematical model of frequency-adjusting behavior was implemented, allowing each robot to dynamically adjust its TF based on signals from other robots. Experiments were conducted under two conditions. First, with a fixed TF, results showed that a TF difference of more than 1 kHz was sufficient to reduce interference. Second, in multi-robot runs, implementing the frequency-adjusting algorithm significantly improved navigation performance and localization accuracy. These findings provide the first engineering validation that frequency-adjusting behavior in bats effectively mitigates acoustic interference, demonstrating its potential application in multi-robot navigation systems.
Hasegawa et al. (Wed,) studied this question.