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.
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.
I am writing to inform you about the film Planetary Defense.
Here is the web address of Planetary Defense directly:
View All Reviews (as .PDF)
Here are a few samples:
Your production is the best there is regarding NEOs, the threat of impact, and what might be done about it.
Rusty Schweickart, Apollo 9 Astronaut; Chairman, ASE-NEO Committee; Chairman B-612 Foundation
“Planetary Defense, the ﬁlm, is a documentary that explores how ill-prepared we are to prevent our own extinction from asteroid and comet impacts. They interviewed all the right people, asked them all the right questions, and leaves the viewer scared for our future, but empowered to do something about it.”
Neil deGrasse Tyson, Astrophysicist and Frederick P. Rose Director, American Museum of Natural History, NYC
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!”
Without exaggeration, I can say this is one of the most important documentaries made. You may quote me on this."
-Sir Arthur C. Clarke, Author, "2001: A Space Odyssey"
“No matter where the next big impact occurs, we’re all in big trouble!”
-Duncan Steel (Space Researcher, Author)
"Great stuff. This is a brilliant documentary: concise, precise, and authoritative."
Duncan Steel, Space Scientist and Author