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.
KeywordsTarget Velocity Range Resolution Ambiguity Function Harmonic Structure Main Ridge
- Doppler factor e
- where c
velocity of sound in air and v=target velocity
exponential frequency modulation
linear frequency modulation
linear period modulation
F.reson./BW (quality factor of a resonator)
signal duration between amplitude points of -6dB
Unable to display preview. Download preview PDF.
- Halls, J.A.T. (1980): An analogue device for the generation of sonar ambiguity diagrams. Animal Sonar Systems (eds. Busnel, R.G. and J.F. Fish), Plenum Press, N.Y. pp. 909–911.Google Scholar
- Johnson, R.A. and E.L. Titlebaum (1972): Range—Doppler uncoupling in the Doppler tolerant bat signal. Proc. 1972 I.E.E.E. Ultrasonics symposium.Google Scholar
- Pye, J.D. (1985): Signals as clues to system performance. Systemes Sonars Aeriens Animaux: Colloque International C.N.R.S., Lyon France.Google Scholar