Echo Delay and Overlap with Emitted Orientation Sounds and Doppler-shift Compensation in the Bat, Rhinolophus ferrumequinum

摘要

The compensation of Doppler-shifts by the bat, Rhinolophusferrumequinum,functions only when certain temporal relations between the echoand the emitted orientation sound are given. Three echo configurationswere used:a) Original orientation sounds were electronically Doppler-shifted andplayed back either cut at the beginning (variable delay) or at the end (variableduration) of the echo.b) Artificial constant frequency echoes with variable delay or durationwere clamped to the frequency of the emitted orientation sound at differentDoppler-shifts.c) The echoes were only partially Doppler-shifted and the Doppler-shiftedcomponent began after variable delays or had variable durations.With increasing delay or decreasing duration of the Doppler-shifted echothe compensation amplitude for a sinusoidally modulated + 3 kHz Dopplershift(modulation rate 0.08 Hz) decreases for all stimulus configurations(Figs. 1, 2, 3).The range of the Doppler-shift compensation system is therefore limitedby the delay due to acoustic travel time to about 4 m distance betweenbat and target. In this range the overlap duration of the echo with theemitted orientation sound is always sufficiently long, when compared withdata on the orientation pulse length during target approach from Schnitzler(1968) (Fig. 5).