A mysterious low-frequency hum emanating from the Earth is likely caused by ocean storms. First discovered by Japanese seismologists in 1998, the vibrations have a frequency between two and seven millihertz, inaudible to humans.
UC Berkeley scientists propose in the journal Nature that the hum is produced by interactions between the atmosphere, ocean, and seafloor. From a BBC News report:
The daily release of energy required to generate the hum is equivalent to a magnitude 5.75 to six earthquake, say Junkee Rhie and Barbara Romanowicz of the University of California, Berkeley.
