The explanations are almost as varied as the sounds themselves. There’s not a single explanation to cover all the mysterious sounds, though many have been identified. For example, there was 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 two days. Terrified residents, the report added, described the noises as a “loud hushing” or “snoring” sound. The sounds were also recorded one night, and later uploaded on YouTube. The Minister of Science, Technology and Innovation had a very simple explanation for it, though – it was created by an oil palm factory testing their boiler pressure on Jan 11 and Jan 12 2012.
In other cases the strange sound is still being researched. In february of last year, the Canadian government was asked to investigate a low-frequency hum that had intermittently plagued citizens in Windsor, Ontario for months.
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 too, 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; 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.
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.
Appart from what I used to think, mysterious sounds are nothing new. 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. And it's not easy to locate a sound, researchers say. 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.