Evaluation of a Simple Model for the Acoustics of Bat Swarms

Abstract

Bats using their biosonar while flying in dense swarms may face significant bioacoustic challenges, in particular mutual sonar jamming. While possible solutions to the jamming problem have been investigated multiple times in literature, the severity of this problem has received far less attention. To characterize the acoustics of bat swarms, a simple model of the acoustically relevant properties of a bat swarm has been set up and evaluated. The model contains only four parameters: bat spacial density, biosonar beamwidth, duty cycle, and a scalar measure for the smoothness of the flight trajectories. In addition, a threshold to define substantial jamming was set relative to the emission level. The simulations results show that all four model parameters can have a major impact on jamming probability. Depending on the combination of parameter values, situations with or without substantial jamming probabilities could be produced within reasonable ranges of all model parameters. Hence, the model suggests that not every bat swarm does necessarily impose grave jamming problem. A fitting process was introduced to describe the relationship between the four parameters and jamming probability, hence produce a function with jamming probability as output and four parameters as input. Since the model parameters should be comparatively easy to estimate for actual bat swarms, the simulation results could give researchers a way to assess the acoustic environment of actual bat swarms and determine cases where a study of biosonar jamming could be worthwhile.