People around the world have reported hearing strange sounds from the skies over the past month. Sometimes they describe it as a hum or low rumble; other times it's a whine, thump, or even a melody. Often the sounds have been recorded and posted online, fueling rumors and conspiracy theories.
One blogger wrote, "either the world is ending, aliens are landing or everyone is getting hoaxed. Or, possibly, there's an actual scientific explanation for the mass amount of YouTube videos capturing bizarre sounds that are being heard around the globe. Are we witnessing the beginning of a full-scale alien invasion?"
So, what are people hearing (and recording)?
The explanations are almost as varied as the sounds themselves. There's not a single blanket explanation for all the mysterious sounds, though many have been identified. For example there's the recent "midnight roar" reported in Malaysia:
According to a Borneo Post report, the "Sky Roar" had been heard over Kota Samarahan from around 2am or 3am till dawn on both days. Terrified residents, the report added, described the noises as a "loud hushing" or "snoring" sound. The sounds were also recorded that night, and were later uploaded on YouTube. The Minister of Science, Technology and Innovation has a very simple explanation – it was created by an oil palm factory testing their boiler pressure on Jan 11 and Jan 12.
In other cases the strange sound is still being researched; last week the Canadian government was asked to investigate a low-frequency hum that has intermittently plagued citizens in Windsor, Ontario for months. (If the conspiracy theorists are right, Canadian Prime Minister Stephen Harper may soon get an unofficial visit from Men in Black-type agents warning him not to investigate.)
There are a few things to keep in mind about these strange, ambient sounds; for one thing, there is virtually no place on the planet where noise pollution is not a problem. We live in a constant sea of background noise, most of it unnoticed until we start paying attention to all the sounds and focusing on them.
Sources of indoor sounds are nearly endless, from faintly ticking clocks to air conditioning to bubbling aerators in fish tanks. Outside the problem is far worse, with noise generated by countless sources including traffic; airplanes (seen and unseen); radios; lawnmowers and snowblowers; trains; highways; and high-tension lines. Then there are the many industrial sources of noise and vibrations, including power plants and any factories with large machines such as auto assembly plants and printing presses.
Some complain that the promise of green energy offered by large wind turbines comes at a cost: a low, rumbling, rhythmic whoosh or groan that travels through the air and earth, sometimes for miles. Furthermore, the earth itself generates a natural, constant hum (though it's typically far below the threshold of human hearing). Scientists believe the hum is created by ocean waves crashing over continental shelves, which creates vibrations that travel throughout the world.
In some cases, the "mysterious sound" videos have been revealed as hoaxes. For example, a college student in Edmonton, Canada, posted a video of mysterious sounds which got nearly 140,000 views on YouTube before she admitted it was fake. She told a local newspaper, "I made the video by taking out my iPhone and merely video recorded my balcony view while holding my laptop right behind it, while my laptop played the Conklin YouTube video in the background. Took less than a minute to do this.... I made the video to show my friends and family how easy it was (literally less than five minutes of my life to make the video and upload it) to make something like that, and how they shouldn't believe everything they see online, and should especially not get fearful."
Mysterious sounds are nothing new, of course. The most famous mystery sound in the world is probably the Taos Hum, a low-frequency rumble heard by some residents in Taos, New Mexico since the early 1990s. Not everyone hears it, but the earwitnesses who do variously describe it as sounding like a running refrigerator or a buzzing bee. Researchers have been unable to pinpoint the source of the sound - or even confirm that the hearers are indeed perceiving a specific, identifiable sound.
While the public may assume that locating a sound is easy, it's not. Identifying the source of a sound is very difficult in urban areas where concrete, glass, and buildings can reflect, change, and amplify sound waves from ordinary sources. Of course it's more fun to think that the mysterious sounds are part of an alien invasion or secret military experiment than machinery at a local sewage plant.