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Fig. 2. Example of an ensonification event, during which an echolocating
Grampus scans each of the three receivers (A,B,C). Note how the
ensonification moves from hydrophone C to B to A. Full amplitude of the
y-axes corresponds to an apparent source level (ASL) of 222 dB re. 1
µPa (pp). Local maxima on each of the three channels are likely to
represent signals on or close to the acoustic axis of the sound beam. X marks
a single click displayed in detail in Fig.
3.