The problem of finding passageways in foliage with biomimetic sonar

Bats living in densely vegetated habitats must have the ability to find passageways in foliage. To explore the sensing problem posed by this navigation task, a sonar head that mimicked a bat's biosonar periphery and emitted a bat-like chirp was placed on a linear track to scan artificial foliages (plastic leaves resembling broad-leaf foliage) interrupted by gaps of controllable width. The first approach to detecting the gaps tested has been based on comparing echo energy levels received when facing a gap as opposed to a closed foliage. The ability to detect a gap in this way depends on the employed beamwidth and the distance to the foliage, i.e., the narrower the beam and closer the sonar head, the narrower a gap can be detected. However, narrower beams were also found to increase the variability in the energy of the returned echoes which could impact the ability to reliably distinguish the different levels of echo energy associated with closed foliage and gaps. Since bats tend to have wide beams due to t...