Unexplained Roaring Sound from Sky over the Alps in Austria

Just days ago reports of mysterious sounds coming out of the mountains in Weining, Guizhou in China went viral.

Now check this which occurred in central Austria in the Alps at around 1,200 meters above sea level of strange roars coming from the skies.

The strange sounds were reportedly 100 times louder then a normal airplane noise, twice for about 6-8 minutes with a 5 minute break between. At first it was thought there must be a huge airplane circling above the clouds, but no aircraft was seen.