Have you heard the Mysterious Sounds?

Mysterious sounds have been heard booming from the sky all around the world - in some cases they were so loud they set off car alarms. The unsettling noises were heard recently from Europe to Canada, sounding like groans and powerful horns. I am posting this 15 minute youtube video, an accumulation of videos that have come in these past months from all over the globe, take a listen.

The internet has been buzzing with theories about what the sounds could be, with scientific explanations such as electromagnetic noise emitted from auroras and radiation belts to ridiculous speculation such as signs of the mayan predicted apocalypse or the big world alien invasion as seen in most motion pictures.

What are these noises and what in the world is going on?