Hi All,
Bob McGuire and Mark Chao shared some interesting comments last week
about individual variation in the songs of the two species of
waterthrushes. For those who are interested in this sort of thing, I
wanted to share some resources at the Cornell Lab of Ornithology's
Macaulay Library (ML) web site that allow users to explore bird sound in
more detail.
The Macaulay Library (ML) is home to over 100,000 digitized sound
recordings, with bird recordings from all over the world, as well as
thousands of mammal, insect, and amphibian recordings. These recordings
can be played at the ML web site: macaulaylibrary.org
If you're interested in analyzing bird sounds in a bit more detail, the
ML web site also features a great tool called RavenViewer that allows
you to see real-time spectrograms for every recording. The instructions
for downloading RavenViewer can be found at the lower right corner of
the ML home page, and it only takes a few minutes to complete the download.
Once you've downloaded RavenViewer and restarted your web browser,
return to the ML web site, and type in a species (such as Northern
Waterthrush) that you're interested in exploring. The Search Results
page will show a list of recordings of that species, and next to each
catalog number, there will be two similar play buttons--a blue one with
a white triangle, and a blue one (again with a white triangle)
surrounded by yellow. Click the blue, white, and yellow button to
listen to the recording while also viewing it in RavenViewer.
A separate RavenViewer window will then open, showing three separate
display panels. The top one is a waveform, which shows the relative
loudness of sounds in a recording. The middle one is a spectrogram,
which shows the frequency of a bird sound against time. The bottom
panel is a power spectrum, and to be honest, I'm not quite sure what
that shows. (I believe it is used mostly for bat recordings.)
When I use RavenViewer, I tend to hide the waveform and power spectrum
panels, and show just the spectrogram. (To hide a panel, select the
relevant tab near the bottom of the browser window, and then select
"Hide.") This makes the spectrogram panel larger, allowing for more
detail. I then select the spectrogram tab, and adjust the Timeline Zoom
and Upper Frequency Limit settings to view individual songs in even more
detail. If I wanted to look at a single Northern Waterthrush song, for
example, I would change the Upper Frequency Limit to 10,000 Hz and set
the Timeline Zoom to something in the 65 to 75 range. (I am no expert
on sound analysis, though, so there might be better settings to use.)
RavenViewer also includes a "Speed" function that allows you to either
slow down or speed up a recording. If you think a Winter Wren song is
amazing at normal speed, try slowing it down to half speed!
Good listening,
Matt Medler
Audio Archivist
Macaulay Library
Cornell Lab of Ornithology
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