Figure 7.

Pulse-echo ambiguity. (A) Spectrograms of one FM echolocation broadcast and the series of echoes generated during flight in the 40-cm corridor by this broadcast from successive rows of chains and then from the end wall. These echoes were recorded by a microphone placed behind the bat early in its flight (when the bat was 6.4 m from the end wall) and aimed to point along the corridor (technique from Hiryu et al., 2010). (B) Cross correlation function between the broadcast and the entire stream of echoes used to compress FM sweeps as a display to maximize visualization of rows of chains. Note epoch of echo reception lasting about 37 ms, corresponding to distance to wall. (C) Plan view of room with superimposed arc sectors depicting distance broadcast travels to reach location where echoes return after 20 ms (dark gray sector) or 40 (light gray sector). If IPIs are shorter than 40 ms, echoes of the first sound in a pair arrive after the second sound is emitted, creating conditions for pulse-echo ambiguity. Longer-delay echoes of the first sound can be mistaken for short-delay echoes of the second sound.