The phenomenon is reported here on io9.
From the story: What exactly are we hearing in these YouTube videos posted by people who claim they’ve recorded ear-splitting roars coming from the sky with no explanation? Here you can see one of the latest, recorded in Budapest, Hungary last week. Conspiracy-lovers are calling them “apocalyptic sounds.” Whatever they really are, they’re freaking creepy. Are they jet engines attached to UFOs, bizarro weather, or pure fakery?
-Annalee Newitz, io9.com
The sounds have been reported in Arizona US, New Zealand, Costa Rica, Alberta Canada, Budapest, The United Kingdom and others. What’s going on? Is it a worldwide hoax? A sign of the Apocalypse? An unknown weather phenomenon?
I leave you with this: