From as far back as 2008, video recordings of strange and disturbing noises that seem to come from the sky have been appearing on the internet. In the last 12 months, many more of these 'strange noise' videos have been recorded and uploaded by people from many different parts of the globe.
The precise origin and meaning of this phenomenon is, as yet, unknown. Are we dealing with a cosmic version of the 'bell tolling' for life on planet earth, or is there a more mundane explanation?
The Sott Report investigates.