There are sound waves so low in frequency that we humans can't hear them, but they may be the secret behind both animal communication and haunted houses. Human ears detect sounds in the frequency range of 20 to 20,000 Hertz (cycles per second). Anything below 20 Hz are called infrasonic waves, which can't be heard by us, but we can experience them as vibrations. It's been discovered that infrasonic waves are present in some of the haunted houses in the U.K. and that they affect human emotions.
At an experimental piano recital, the music had bursts of infrasound in it. After it was over, people were asked to record their mood at particular times during the concert. Some people reported feelings of calmness and euphoria when the infrasonic pipes were switched on. "This is not a new phenomenon; church organ builders have been using infrasonic pipes for over 250 years to create a sense of awe in congregations," says Sarah Angliss, an engineer and composer.
Nobody could figure out how elephants communicated with each other over long distances, until Dr. Katy Payne realized that vibrations in the air near an elephant enclosure at a local zoo reminded her of standing near the organ pipes when she sang in a church choir. Her investigation revealed that elephant calls range from 5 Hz (in the infrasonic range) to 50 Hz (the audible range), and can travel many miles.
Blue whales also use infrasonic waves to communicate. Low frequency sound waves travel huge distances in water, allowing the whales keep in touch over hundreds, if not thousands, of miles. However, this is being threatened by noise pollution created by ships, submarines and drilling operations, which create large amounts of infrasound in the ocean. Researchers think this may be one of the reasons so many whales are becoming separated from their pods and beaching. Some whales use huge bursts of infrasound to stun giant squids before eating them.
Infrasonic waves can also be used as weapons. Since the 1950s, scientists have been developing infrasonic devices which produce acoustic waves in the 1 to 10 Hz range. These cause vibrations inside the bodies of the enemy, incapacitating them for hours or even days, sometimes leading to death. They could also be used for crowd control or self-protection.
Waves of infrasound can be detected around 3,000 miles away from a nuclear blast, which is one way we would be alerted if a bomb went off. An asteroid exploding in the atmosphere would set off the same kind of sound waves, which could be dangerous if it was mistaken for a nuclear blast. These waves can also warn us about earthquakes, volcanoes and avalanches, not to mention those haunted houses.
Some people think that crop circles are caused by sound waves. Read about this and other scientific theories in ?The Deepening Complexity of Crop Circles? by Eltjo Haselhoff, click here and ?Mysterious Lights and Crop Circles? by Linda Howe,click here.
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