According to Wired.co.uk, the source of the Earth's 'humming' noise may have been found:
A strange bell-like ring emitted by the Earth has left oceanographers confused for decades, but a new study may have found an explanation.
The low-frequency sound, which is inaudible to human ears but can be detected by seismic instruments, has frustrated scientists since the 90s. Theories suggested everything from electromagnetic radiation to earthquakes and secret military operations might be to blame. Although the sound is almost certainly too faint for humans to hear, some people claim to be plagued by a "tinnitus"-like noise -- including many residents of Bristol in the 70s, who said the sound caused headaches and even nosebleeds.
Link to research paper.[abstract only]
(Score: 4, Interesting) by Dunbal on Tuesday April 21 2015, @11:57AM
There's a big chunk of rock significantly close enough to Earth to exert a significant gravitational pull. The Earth's rotation next to it exerts tidal forces, but the gravitational pull acts on rock too. While rock isn't flexible enough to cause tides I'm sure there's at least some periodic creaking generated.
(Score: 2) by wonkey_monkey on Tuesday April 21 2015, @04:20PM
Not the cause of this humming
Not the cause of which humming? The one the paper is saying is down to waves?
systemd is Roko's Basilisk