| Summary: | Schematic showing experimental setup and spatial criterion for on-axis click selection in the (A) vertical and (B) horizontal planes. The radiation pattern of an echolocation click is shown where the passive sonar equation was applied. The source level (SL) is the sound pressure level calculated from the received level (RL) and transmission loss (TL) on the acoustic axis; apparent source level (ASL) is the sound pressure level calculated for off-axis clicks/clicks of unknown recording aspect. Vertical on-axis clicks were isolated when the whale’s acoustic axis (i.e. the maximal intensity of the whale’s beam) was vertically centered on the array which was determined by -3dB beam width calculations. For each scanning sequence (i.e. click train with first ascending then descending amplitudes), the highest intensity click was isolated as a horizontal on-axis click where the whale was pointing its beam towards the array (not to the left or right), assuming constant SL.
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