Scientists capture Earth's 'hum' on ocean floor for 1st time
Europe-based researchers have successfully quantified Earth's vibrational "hum", observable in the absence of earthquakes, using seismometers on the ocean floor for the first time. The low-frequency signals, inaudible to the human ear, have previously been suggested to come from ocean waves and atmospheric turbulences. The findings would help  map the Earth's interior better, said researchers.