Design of a dynamic sonar emitter inspired by hipposiderid bats

Abstract

The noseleaves of Old World leaf-nosed bats (family Hipposideridae) and the related horseshoe bats (Rhinolophidae) are notable for their elaborate static geometries and a conspicuous dynamics in which the noseleaves change their shapes during biosonar pulse emission as a result of muscular actuation. Whereas the noseleaves of horseshoe bats have already been used as an inspiration for dynamic sonar emitter prototypes, the possible functional role of the specific static and dynamic noseleaf features of Old World leaf-nosed bats have yet to be investigated in this manner. To accomplish this, a dynamic emitter based on the time-variant morphology of Pratt's roundleaf bats (Hipposideros pratti) has been designed. The baffle shape was simplified from a tomographic reconstruction of a biological sample. Five shape features (anterior leaf, sella, lancet, and the two nostrils) were preserved in the model. Motions of these parts were derived from three-dimensional reconstructions of landmark points that were placed on the noseleaf of echolocating bats and recorded with a stereo pair of high-speed video cameras. Actuation mechanisms driven by three stepper motors (one for lancet and sella, one for both nostrils, one for the anterior leaf) were implemented to reproduce the dynamic noseleaf motion pattern observed in the bats.