Emission baffle deformations in bat biosonar and biomimetic systems

Abstract

Old-World leaf-nosed bats (Hipposideridae) and horseshoe bats (Rhinolophidae) are two families of echolocating bats that emit their biosonar pulses through nostrils which are surrounded by elaborated baffle shapes (“noseleaves” ). Prior work has shown that the noseleaves change shape in synchrony with ultrasound emission. These deformations involve at least two noseleaf parts with static (geometric) as well as dynamic complexity. To investigate how these deformations could be used in bioinspired systems, data has been collected from bats recorded with microphone/camera arrays as well as a biomimetic sonar head with a biomimetic noseleaf model inspired by Pratt's roundleaf bats (Hipposideros pratti). Both sets of experiments have produced qualitatively similar results that show an emitted wave field which depends on frequency, direction, and also time. Furthermore, the results obtained with the biomimetic noseleaf have demonstrated that noseleaf deformations during ultrasound emission can result in an enhanced information-encoding capacity. Current work is aimed at establishing whether this enhanced coding capacity can be utilized to improve performance, especially in sensing tasks that are related to the natural environments in which the bats' biosonar systems operate. It also needs to be established how much detail needs to be mimicked in an engineered system to harness these effects.