Drew Panko wrote:
> A few years ago I looked at the Tremolo call
> of the eastern screech owl on an oscilloscope.
>
> An it struck me that it could be an interference
> pattern formed as the bird sang two slightly
> different notes in each syrinx.
>
> It might be interesting to look at with some of the
> modern computer sound analysis programs.
Many of the frogs have calls that are made of a number of distinct
frequencies. What we hear as a trill is often just the interference
patterns between these frequencies. Often this also is what determines
if the call sounds smooth, where the frequencies compliment each other,
or harsh, where they don't.
You can see this sort of thing on sonograms. Or in a simpler form in the
waveform displays, which are similar to your oscilloscope display.
Since frogs also don't have a syrinx, it's even more interesting to
speculate how they sing a half dozen or more distinct frequencies
simultaneously. Clearly the ideas on what sort of structure it takes to
produce multiple frequencies need a bit of thinking through. I believe
having two syrinx's will allow the singing of two independent songs, but
appears not to be a requirement for singing multiple frequencies.
Your screech owl call might be produced the same way as the frog one,
interference between distinct frequency components. Though I think it
also relates to airflow modulation.
Walt
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