Sky sounds

Sky sounds are typically not from the sky at all, they're just various human-made and natural environmental sounds being creatively misinterpreted on the internet as something weird. Like alien battleships maneuvering in deep space, or extraterrestrials generating an auditory version of the Arecibo answer, or the evil effects of HAARP and Project Blue Beam, or trumpets blown by angels announcing the second coming of Christ.

Origin
Probably inspired by 2012 apocalypse paranoia, videos claiming to capture mysterious groaning, screeching, humming, and crashing noises emanating from the sky first appeared on YouTube in 2012. The initial viral video originated from Kiev, Ukraine, and featured a crowded city view accompanied by occasional deep metallic groans. Mucho hits ensued, and news-of-the-weird and tabloid press outlets helpfully spread the idea plus a crapload of hyperbole about the sounds (so-called "Unidentified Audible Objects" i.e. UAOs) heard in other locations.

Hoaxes
YouTube prankmeisters expertly dubbed the sound from the original Kiev video onto copycat videos claiming to record the strange sky sounds in various countries, encouraging the idea that the sounds were being heard "all over the world".

Misinterpretations
The supposedly "mysterious" noises are likely just ordinary human-made industrial sounds such as construction activity, heavy cranes moving, or underground tunneling operations. In addition, natural sounds such as wind blowing through geologic formations or human-made structures like power lines or microwave towers, small seismic events, and waves crashing offshore, can all be distorted or enhanced by atmospheric conditions to sound like they are coming from some unknown direction.

Crank magnetics

 * Christian fundamentalists embraced the reported sounds as evidence of celestial trumpets foretold by the Bible to herald the Second Coming of Christ and signal the end of the world. This notion got some real traction on the internets, helped along by comparisons to a scene in the Kevin Smith film Red State depicting apocalyptic trumpet sounds, and caused no small degree of agitation on Christian message boards among those convinced the end was truly near.


 * UFO nuts interpreted the sounds as alien space ships zooming around the earth prior to invasion. Some UFO believers even speculated that it was an alien civilization attempting to answer the Arecibo message, but why aliens would choose to communicate using sounds resembling a truck dragging a garbage skip is anybody's guess.


 * Conspiracy theorists were convinced the sounds were part of Project Blue Beam's plan to subjugate the populace using HAARP technology to saturate the ionosphere with mind-numbing sonic waves.

How to hear them
The next time that you hear any exterior sound that you can't immediately identify, think this can't possibly be natural, human-made or harmless, this must be _____ (fill in the blank with any of the following):


 * the return of Jesus!
 * the work of Satan!
 * an insidious Government conspiracy!
 * the beginning of the New World Order!
 * a message from Aliens!
 * a test run of Project Blue Beam!
 * a mind-control attempt by HAARP!
 * A giant monster like in the movies!