What is baudline?
Mystery Signal
Mystery Signal of the Month   Aug 20 2002
We've got signal, but what the heck is it?
That's your mission.  Analyze this bébé.

mystery spectrogram                                                                                                                                                          

download the audio file 9.wav.gz

hints :

  • No need to gunzip this file since baudline can automatically uncompress files.
  • Setup baudline to be a Web Browser helper application as described in the FAQ.
  • In the play deck, turn on the 60 Hz notch filter and set the digital gain boost to +36dB.

What is it?

A baudline user wrote in:

    I thought that I would note that your "mystery signal" is from a critter I used to call by whistling.  The originator is very good wrapped in bacon and stuffed with wild rice and shallots.
Bacon?  Yes, the mystery signal is indeed that of the Mourning Dove (Zenaida macroura).  What is interesting about the dove's call (and others in the Columbidae family) is that it is an octave or two lower than calls made by birds of similar size.  The generation of the low frequency call involves an inflated air sac.  The standard piston model states that each halving of frequency requires a +12 dB increase in excursion.  So in comparison to other birds, this is a significant increase in energy.  The spectrogram display has what looks to be a spin up and spin down for each note.  Nothing is actually spinning here but think of the dove's low frequency call as a large air mass in motion that doesn't start or stop instantly.  It takes time and effort to move a larger mass which would explain the leading and trailing tone sweeps.

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