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Blue whales off the California coast make calls that, sped up 10 times, sound like (sound of two-part call). The original is a wall-rattling frequency too low for us to hear. Scientists analyzed around 2,500 of those calls, and found that the second part (sound) is nearly ___1___ in pitch every time from each whale: 16 hertz, or four octaves below middle C. And the slight ___2___ in frequency that do exist are only a tenth of the difference between a C and a C sharp. Those findings appear online in the Journal of the Acoustical Society of America.
The researchers don't know how many different individual whales they caught singing, or why even they sing at all. But past studies suggest only blue whale males make calls like this. So the investigators speculate that males might ___3___ to a single common pitch as a sort of ___4___.
Thanks to the Doppler effect, females swimming towards a male would hear a slightly higher pitch; swimming away, a lower-pitched moan. Serenade ___5___—you might be swimming solo tonight.