The side-bands are indeed revealed by spectrographic analysis. Bradbury and
Vehrencamp's book Principles of Animal Communication (1998; Sinauer:
has a good treatment of harmonics, amplitude modulation, frequency modulation,
beats. It's worth reading if you're trying to puzzle these out. Or even if
not, as it's a good book.
The relative strength (intensity) of the various sidebands could indeed be
caused by a
sound propagation effect. For instance, a reflection off the surface or
increase or decrease the intensity of a certain sideband, depending on whether
was constructive or destructive interference (respectively) between the
sound and the reflected-path sound. The frequencies affected could change
of the whale or hydrophone, or simply with the distance between hydrophone and
Or the whale could be altering its sound production too.
At 06:03 PM 7/30/02 -0400, you wrote:
>From: Harald Yurk <[EMAIL PROTECTED]>
>Subject: Energy distribution in pulsed vocalizations
>To: [EMAIL PROTECTED]
>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
>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.
>Department of Zoology
>Marine Mammal Research Unit
>University of British Columbia
>6270 University Boulevard
>Vancouver, B.C., Canada V6T 1Z4
>From Thu, 11 Jul 2002 09:15:26 -0700
From: nikolas francis <>
Date: Thu, 11 Jul 2002 09:15:26 -0700
Subject: Rat vocalizations
Hello, my name is Nikolas Francis. I am a senior at The University of Iowa
and this fall I will be involved in a research project which requires as many
different rat vocalizations as possible to be played to a group of rats. I
thought this would be a good place to ask if anyone knows of a good source to
find recordings of rat vocalizations. If you know of any people or sound
banks that would help, please let me know. Thank you.
The University of Iowa