Last week was a busy one for the Comprehensive Test Ban Treaty Organization, a detection agency set up to identify nations when they test nuclear weapons banned by treaty. On Tuesday, the organization's seismographs detected a rumble in North Korea that could only have been an atomic test. Then on Friday, CTBTO infrasound sensors picked up an explosion over Russia, but this time, it wasn't a nuclear test. Instead, the sensors picked up short-frequency sound waves from the Chelyabinsk meteor blast. The blast was so powerful that sound waves were detected as far north as Greenland and as far south as Antarctica. Scientists quickly determined that the event was a meteor, not a nuclear weapon, because the sound-wave pattern indicated a moving object.
If you want to hear the sound yourself, the CTBTO has released audio from the explosion. Infrasound is too quiet to be heard by the human ear, so researchers modified the data to make it audible:
In the months to come, researchers will look over the data picked up by these infrasound sensors to learn as much as possible about the meteor. While set up to monitor rogue nuclear tests, the sensors put in place by the CTBTO are in the meantime capturing scientific data we would have otherwise missed.
Five amazing, clean technologies that will set us free, in this month's energy-focused issue. Also: how to build a better bomb detector, the robotic toys that are raising your children, a human catapult, the world's smallest arcade, and much more.


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Just for the record, I believe that infrasound is just at too low a frequency to be heard by most. The source that I checked said that it was anything below 20Hz.
If it had been too quiet, they would have amplified it -- not generally described as 'modifying the sound'.
Instead they did something to shift te frequency up into a better region. They could have used an oscillator and hetrodyned it, but that's probably too old school in this digital age.
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Comments/Reviews:
View All Reviews (as .PDF)
www.spaceviz.com/img/Planetary_Defense_comments.pdf
Here are a few samples:
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Rusty Schweickart, Apollo 9 Astronaut; Chairman, ASE-NEO Committee; Chairman B-612 Foundation
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Neil deGrasse Tyson, Astrophysicist and Frederick P. Rose Director, American Museum of Natural History, NYC
Planetary Defense
Who will save Earth?
Scientists and the military have only recently awakened to the notion that impacts with Earth do happen. "Planetary Defense" meets with both the scientific and military communities to study our options to mitigate an impact with Earth from large meteors, asteroids and comets, collectively known as NEO's (Near Earth Objects). “Civilization is ill prepared for the inevitable. It's not if an impact will happen with the Earth, it's when!”
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