Dynamic echo signatures created by a biomimetic sonar head

Abstract

Certain bat species (e.g. horseshoe bats, family Rhinolophidae) are known for conspicuous deformations of the emission baffles (noseleaves) and reception baffles (ears). Previously reported numerical studies and experiments with biomimetic reproductions of these baffles have shown that such deformations can result in time-variant emitter/receiver characteristics. However, it has not been investigated whether these time-variant characteristics could also manifest themselves in likewise time-variant properties in echoes from targets of varying complexity. To investigate this question, a biomimetic sonar head complete with deformable emission and reception baffles has been used to ensonify targets with different simple geometries (sphere, cylinder, and cube) as well as random, more natural target geometries (artificial plants) from distances of about 1 meter. Time-variant echo signatures were found in all these cases, i.e. irrespective of target complexity and whether the time-variance was injected into the emission, the reception, or into both. This demonstrates that although the time-variant emission/reception characteristics had been previously measured only under careful conditions, they are capable of impacting real-world echoes. Even targets with distributed clouds of scattering facets did not obscure the effects of the changing conformation states. Hence these changes in ear position created by baffle deformations could serve the animals or man-made sonar systems that mimic them to encode additional echo information through time-variant echo signatures.