Abstract
The big brown bat (Eptesicus fuscus) produces echolocation sounds in its larynx and emits them through its open mouth. Individual mouth-opening cycles last for about 50 ms, with the sound produced in the middle, when the mouth is approaching or reaching maximum gape angle. In previous work, the mouth gape-angle at pulse emission only weakly predicted pulse duration and the terminal frequency of the first-harmonic FM downsweep. In the present study, we investigated whether the dynamics of mouth opening around the time of pulse emission predict additional pulse waveform characteristics. Mouth angle openings for 24 ms before and 24 ms after pulse emission were compared to pulse waveform parameters for three big brown bats performing a target detection task. In general, coupling to the air through the mouth seems less important than laryngeal factors for determining acoustic parameters of the broadcasts. Differences in mouth opening dynamics and pulse parameters among individual bats highlight this relation. [Supported by NSF and ONR.]