Figure 1.

Schematic drawing illustrating the conditions for overlap between emitted signal, prey echo and background echoes a bat encounters when foraging at a distance of 5 m to vegetation. The prey echo overlaps with the emitted signal when an insect flies in the signal overlap zone and with the clutter echoes from the background when it flies in the clutter overlap zone. In the overlap-free window no overlap occurs. The width of the overlap zones depend on signal duration. At durations between 10 and 2 ms, the overlap zones range between 1.70 and 0.34 m, if a sound speed of 340 m/s is assumed. A reduction of signal duration by 1 ms reduces the width of each overlap zone by 0.17 m and thus increases the width of the overlap-free window by 0.34 m.