Reconstruction of bat sonar beams using a multichannel microphone array

Abstract

We reconstruct the sonar beams emitted subsequently by flying bats from recordings of a two-dimensional microphone array. Based on the bats’ position in space, which can be accessed through a infrared 3D-video system, and the simultaneous recordings of 16 small microphones, the sonar beams emitted by the bats and the sonar footprints on arbitrary planes can be estimated. For the interpolation of a continuous sonar beam at different frequency bands, directional frequency responses, atmospheric and geometric attenuation, and different lag times are taken into account for each microphone. Mean and maximum call intensities can be analyzed and various analysis parameters can be adjusted, different visualizations are available, and numerical data are exported. The system provides access to estimations of the maximum intensity of each call in front of the bat, beam width, shape, and intensity for arbitrary frequency bands, the aiming of the beam, and the bat’s scanning behavior on its flight path.