The sound emission pattern of the echolocating bat, E p t e s i c u s f u s c u s

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Abstract
The emission pattern of Eptesicus fuscus was found to be consistent with those of the other frequency-modulating (FM) bats studied in similar detail in that there is a mainlobe aimed forward of the animal together with a prominent - 6-dB ventral lobe. This ventral lobe cannot be explained as the first sidelobe of a piston source mounted in an infinite baffle and must be formed by some other acoustic means. Nevertheless, a piston source with a radius comparable to that of the open mouth can nicely explain the changes in the width of the mainlobe with frequency, so that the open mouth alone can explain the observed directionaliy. At wavelengths greater than the mouth dimensions, however, some additional sound "focusing" may occur, presumably due to diffraction by the head.