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INFRASOUND AT A GLANCE
Infrasound is a low frequency sound below the range of human hearing. It is produced by a variety of natural events - including earthquakes, volcanoes, avalanches, severe weather, ocean waves - and some man-made sources - including aircraft and explosions. It is also used by some animal species to communicate.
How is it different from audible sound?
One of the most interesting properties of infrasound waves is that they travel over global distances without losing their strength. So an instrument in Colorado can detect the sound of ocean waves hitting the coast in California or the roar of a typhoon halfway around the world.
How is it detected?
Infrasound wavelengths are so long that they can be detected only by sensors that take up a large ground area.
What is it used for?
A global infrasound sensor system is being deployed to detect nuclear weapons testing. Scientists are also studying ways to use infrasound to provide advance warning of natural disasters.
Read more: www.sfgate.com...
Originally posted by infoseeker26754
Sorry to say I have not heard any of them sounds as of yet. Actually I am in the middle of the US, 300+ miles to any big city so just wondering if anybody has placed out a map and pinned each sound?
Could give some clues to where they might be coming from. Did hear though its happening all over so might have to make a world map! Good part is if the Angels were blowing, we would all hear it!
I just feel left out sometimes!
Originally posted by purplemer
I have always thought the sky noises might come from the earth and use the sky as a giant amplifier..
HOWEVER the subducting plate doesnt reach 150 Km until it reaches (The Super Volcano) Yellowstone Nation park ,WY.
At about 150 Km depths, reactions occurring in the subducting plate release water into the overlying mantle, thus lowering the melting temperature of mantle material.
Originally posted by westcoast
I looked this up ofcourse, and discovered that is most likely an Upper Tangent Arc:description
Only thing is, typically you see it 'attached' to a sun halo...but as you can see, there wasn't one. I really think this type of arc is quite rare around here.
The dynamic range of the auditory system decreases with decreasing frequency. This compression can be seen in the equal-loudness-level contours, and it implies that a slight increase in level can change the perceived loudness from barely audible, to loud. Combined with the natural spread in thresholds within a population, it may have the effect that a very low-frequency sound which is inaudible to some people may be loud to others.
Recordings and playback experiments support that elephants use the infrasonic components of their calls for communication. Infrasonic vocalizations have been recorded from captive elephants in many different situations. The structure of the calls varies greatly but most of them range in frequency from 14 to 24 Hz, with durations of 10–15 seconds. When the nearest elephant is 5 m from the microphone, the recorded sound pressure levels can be 85 to 90 dB SPL. Some of these calls are completely inaudible to humans, while others have audible components that are probably due to higher frequency harmonics of below 20 Hz fundamentals.