Dear List Members
I am studying the behavioral use of pulsed vocalizations by killer whales.
As many of you know those cetaceans produce discrete calls that can be
easily recognized by their spectrographical side band structure of their
pulsed vocalizations.
When calls are recorded with a single hydrophone, the greatest energy
measured from the spectrogram can be found on either one of those side
bands. As I understand it, those side bands are produced by an artifact of
the spectrographical analysis because a Fast-Fourier-Transformation always
assumes the existence of harmonics. The side bands, however reflect the
pulse repetition rate of pulsed signals (Watkins 1966). What I am curious
about and don't really understand, is why the highest energy is not always
found on the same side band. Are other physical conditions outside of the
sound producing whale responsible for those differences, or does body
movement affect the energy to shift between sidebands or .. ?
Maybe someone with better understanding of physical acoustics than myself
can help with this. Thank you very much.
Best regards,
Harald
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Harald Yurk
Department of Zoology
Marine Mammal Research Unit
University of British Columbia
6270 University Boulevard
Vancouver, B.C., Canada V6T 1Z4
Phone:(604) 822-8181
Fax:(604) 822-8180
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