It's tough without bird ears, because we're really only talking about like a few hundred hertz, which is why the scientists use these things called spectrograms.
Once a database of dolphin sounds was created, the program identified subsequent dolphins by their sounds nearly as well as humans who eyeballed the whistles' spectrograms.
We feed the computer these spectrograms that we've classified as one species or another, and then, as we repeat that thousands and thousands of times, the computer learns to be able to distinguish one species from another.
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During the autumn and winter of 1912, he obtained a series of spectrograms from the largest of the spiral nebulae, which was located in the constellation of Andromeda and known at the time as the Andromeda Nebula.