Bat biosonar as an inspiration for dynamic sensing

Abstract

Sensory systems found in biology continue to outperform their man-made peers in many respects. In particular, their ability to extract salient information from complex, unstructured environments is often superior to engineering solutions. Bat biosonar is an example for an exceptionally powerful yet highly parsimonious sensing system that is capable of operating in a wide variety of natural habitats and achieve a likewise diverse set of sensing goals. One aspect in which bat biosonar appears to differ from man-made system is its heavy reliance on diffraction-based beamforming with intricate baffle shapes. In-vivo observations of these shapes have provided evidence for non-rigid baffle deformations that coincide with the diffraction of the outgoing or incoming waves. In horseshoe bats, a bat group with one of the most elaborate biosonar systems, the emission baffles have been found to twitch in synchrony with each pulse emission. On the reception side, the animals’ outer ears can likewise be deformed while the incoming pulses impinge on them. The acoustic effects of the outer ear motions can be characterized using frequency-domain characterizations (beampatterns) revealing significant acoustic effects. However, a time-domain characterization of a biomimetic prototype has shown even stronger effects. Hence, it may be hypothesized that these mobile baffle provide a substrate for a time-variant strategy for the encoding of sensory information - a hypothesis that is well suited for further exploration with bioinspired sensing technology.