Schuller, Gerd and Suga, Nobuo
Storage of Doppler-Shift Information in the Echolocation System of the "CF-FM"-Bat, Rhinolophus ferrumequinum.
In: Journal of Comparative Physiology A, Vol. 105: pp. 9-14
The greater horseshoe bat (Rhinolophus ferrumequinum) emits
echolocation sounds consisting of a long constant-frequency (CF) component
preceeded and followed by a short frequency-modulated (FM) component.
When an echo returns with an upward Doppler-shift, the bat compensates
for the frequency-shift by lowering the emitted frequency in the subsequent
orientation sounds and stabilizes the echo image. The bat can accurately
store frequency-shift information during silent periods of at least several
minutes. The stored frequency-shift information is not affected by tone
bursts delivered during silent periods without an overlap with an emitted
orientation sound. The system for storage of Doppler-shift information has
properties similar to a sample and hold circuit with sampling at vocalization
time and with a rather flat slewing rate for the stored frequency information.