Strange Sounds
© YouTubeA woman reacts to hearing a strange noise coming from the sky in Texas.
Have you heard those weird, apocalyptic trumpet-like noises coming from the sky? People all over the world say they have.

So what are they? The short answer is no one knows.

The latest video of the mystery comes from Germany and was posted to YouTube last month.

In it, the puzzled photographer sticks a camera out the window as a woman asks in German, "What is that?"

In the background is heard a metallic-type groaning sound coming from the sky as if someone just put the key in the ignition of a large, invisible Close Encounters of the Third Kind kind of vehicle and started it up. The video is all the more eerie because a young boy is standing motionless in the street as the noise amplifies.

Take a listen. What do you think that is?

The sounds have been reported over the last several years from California to Texas to Australia and many parts in between. The website, which chronicles the incidents, has compiled a list of more than 150 videos of the audible weirdness.

The phenomena has been described variably as the blare of a trumpet, a groaning metallic sound, an airplane engine, a loud rumbling, even humming.

So what's really causing the noise?

The rumor-debunking website Snopes says that scientists point to natural causes, such as earthquakes, tidal waves, methane explosions and even shifting sand dunes, as the possible reasons for the aural oddities.

David Hill, a U.S. Geological Survey scientist, said that small earthquakes below the surface can transmit sounds of the earth's cracking crust. He also said that the emissions could come from meteors.

Midshipman fish
© WikipediaMidshipman fish.
Other theories include electrical power lines, electromagnetic radiation, high pressure gas lines, wireless communications devices, submarines and - saving the best for last - the reverberating mating call of a male Midshipman fish. (Can't make this stuff up.)

One poster had this to say: "I think people are so accustomed to hearing these sounds in their back yards ( I hear them in mine) they don't realize that this is not normal, it is the hidden machines being used to control the weather and sometimes to cause quakes. They are weapons hidden among us."

Other guesses include God's trumpets, aliens, the slippage of the planet's core and earth's growing pains.

Some even point to HAARP, aka the U.S. government's High Frequency Active Auroral Research Program, a research program that analyzed the ionosphere with the aim to develop enhancement technologies for radio communication and surveillance.

Conspiracy theorists claimed the program, which was shut down last year, was really an effort to control everything from the weather to people's minds.

The videos could also be totally fake. One woman who posted a "strange sound" incident to YouTube later admitted all she did was point her iPhone out the window as her laptop played the soundtrack behind her.

But the couple in Germany who posted the latest video said theirs was definitely not a hoax.

Here are a sample of the videos posted by perplexed participants in the "great weird noises from the sky" phenomenon.

As one of the scientists in this famous movie said: "I hope someone is taking all this down."