Since the 1970s, people across the world have reported hearing an inexplicable low-frequency droning. Scientists now think they know what it is.

For decades, seismologists have known that Earth is never completely still, even when no earthquakes are happening and no volcanoes are erupting. Sensitive instruments worldwide record a continuous ...

The global "hum" of the Earth is now helping scientists probe the planet's deep interior, a group of researchers say. Since this hum — called seismic noise, which is generated by sources such as storm ...