Figure 2.

Echoes from the clutter (holes) and target (dipole cylinders) were measured by projecting a 1 ms long FM signal (sweeping from 110 to 15 kHz), similar to the bat’s echolocation emissions, from a 2 cm electrostatic loudspeaker and recording the echoes with two condenser microphones. To make the dipole echo measurements, the cylinders were placed in the foam holes with a specific protrusion height (12, 8, 4, or 2 mm) and the entire scene was ensonified to generate reflections.