Artificial Pinnae for Imitating Spatial Target Localization by the Brown Long-Eared Bat (Plecotus auritus)

Echolocating bats locate a target by echolocation and their performance is related to the shape of the binaural conformation in bats. In this study, we developed an artificial sonar system based on the vertical sound localization characteristics of the brown long-eared bat (Plecotus auritus). First, using the finite element method, we found that the beam of the first side lobe formed by a pinna constructed according to that in the brown long-eared bat shifted in an almost linear manner in the vertical direction as the frequency changed from 30 kHz to 60 kHz. We established a model of the relationship between the time-frequency features of the echo emitted by brown long-eared bats and the spatial direction by using the pre-trained neural network. We also developed a majority vote-based method called sliding window cumulative peak estimation (SWCPE) to optimize the outputs from the neural network. In addition, an L-shaped pinna structure was designed to simultaneously estimate the azimuth and elevation. Our field experiments indicated that the binaural conformation and relative binaural orientation both played vital roles in spatial target localization by these bats. Accurate echolocation can be achieved using a simple binaural sonar device even without binaural time difference information.