Harmonic Structure of Bat Echolocation Signals

A wide range of different harmonic patterns is found in echolocation signals of bats. Often a gradual change from single harmonic pulses to multiple-harmonic ones can be observed when FM-bats detect and approach their prey in free flight. Multiple-harmonic pulses may also be used for orientation in space under reverberant conditions or for target discrimination. The appearance of the harmonic structure of a bat pulse is influenced by the Q of vocal tract resonances. At low Q multiple harmonics increase the signal bandwidth and thus improve the ranging and discriminative properties of a pulse. At high Q dumbell pulses are created.