Strange Noise heard in Germany sets off car alarm

http://www.youtube.com/watch?feature=player_detailpage&v=CNql-wSfM0A

These strange sounds are being heard all over the planet, but no one has yet identified what they are. So many guesses...but it's not being reported in mainstream media. Too scary and would raise too many questions that can't/won't be answered.  Check out the right sidebar when you go into this link -- there are so many other reports...WHAT IS THIS?