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Scientists were able to monitor mysterious sounds through giant solar balloons equipped with sensitive microphones sent to an altitude of 70,000 feet from the surface, where they entered the heart of the second layer of the Earth’s atmosphere known as the “stratosphere”.
NASA explained that the thin, dry air in the “stratosphere,” where jet planes and weather balloons reach their maximum height, is a relatively calm layer of air that is rarely affected by turbulence.
And the “stratosphere”, according to the US Space Agency (NASA), is the second layer of the Earth’s atmosphere, and at its lowest level there is the ozone layer, which absorbs and dissipates the sun’s ultraviolet rays, according to what was reported by “CNN”.
Inspired by his study of the low-frequency sounds produced by volcanoes, Daniel Bowman, principal scientist at Sandia National Laboratory in New Mexico, is exploring the acoustic landscape of that layer of the atmosphere. This phenomenon is scientifically known as ultrasound, which the human ear cannot hear.
Bowman and his team previously installed cameras on weather balloons to capture images of the black sky above and the earth below, and then successfully built their own solar balloon.
He also proposed attaching infrared recorders to balloons to record the sounds of volcanoes, in collaboration with his advisor, Jonathan Lees of the University of North Carolina.
“We decided to go ahead and explore what this new platform could do, in collaboration with Jonathan Liss, who is an earth, ocean and environmental scientist with experience in seismological and volcanological research.
According to Bowman, these balloons are equipped with sensors that are twice as fast as commercial aircraft.
-“In our solar balloons we have recorded chemical explosions, thunder, ocean waves crashing, helicopters, city sounds, additional rocket launches, earthquakes, freight trains and jet planes,” Bowman said in an email. “We have recorded other sounds, but their origin is unclear.”
-In a recording Bowman shared from a NASA balloon orbiting Antarctica, the ultrasound of crashing ocean waves sounds like a continuous sigh, but the explosions and other shocks are of unknown origin.
Bowman said, during that participation, that “inside the stratosphere some planes had mysterious infrared signals a few times an hour, but their source is completely unknown.”
Bowman and his assistants conducted the research using NASA balloons and other aviation service providers, but decided to build their own balloons, each 6 to 7 meters in diameter.
The researchers tracked their balloons using the Global Positioning System (GPS) as they traveled hundreds of miles before landing in remote locations.
Sarah Albert, a geophysicist at Sandia National Laboratories, investigated an “acoustic channel” (a channel that transmits sounds over great distances through the atmosphere) located at altitudes identified by Bowman’s research.
Sarah’s recordings have captured missile launches and other unknown sounds. In turn, Bowman said: “This sound may be trapped in the channel and reverberate until it is completely distorted.”
Bowman and Sarah Albert will continue to investigate the atmospheric acoustic channel and try to determine the source of the “strange sound” in the stratosphere, and why some flights record it while others do not.
