|Earth as photographed from the Apollo 11 spacecraft during its first lunar landing mission (Wikimedia)|
NASA's twin Radiation Belt Storm Probes have recorded audio-frequency radio emissions coming from Earth.
"It's called chorus," said Craig Kletzing of the University of Iowa, whose whose team built the EMFISIS (Electric and Magnetic Field Instrument Suite and Integrated Science) receiver used to pick up the signals. "This is one of the clearest examples we've ever heard."
"Some say the signals sound like whales," reports Spaceweather.com, "others liken them to the chirping of prairie dogs. What do you think?"