A repetitive infrasound sound was discovered in the stratosphere by a solar-powered balloon operation. Scientists are unsure of the source of the sound.
Unidentified sounds were heard by scientists high in the Earth's atmosphere.
Researchers at Sandia National Laboratories carried a microphone into the stratosphere about 31 miles (50 km) above Earth's atmosphere in a solar-powered balloon. Due to the relative stillness and absence of storms, turbulence and commercial weather activity in this region, microphones in this layer of the atmosphere can pick up both natural and man-made sounds from our planet.
But the microphone in this study also detected unusual sounds that were repeated several times an hour. Their source has not yet been identified. Sounds are captured in the infrasound spectrum at frequencies of 20 hertz (Hz) and below, which is significantly beyond the range of human hearing. According to Daniel Bowman of Sandia National Laboratories, “mysterious infrasound signals occur several times per hour on some flights, but their origin is completely unknown.”
Bowman and his team used microbarometers, which can detect low-frequency sounds and were originally created to monitor volcanoes, to collect acoustic data from the stratosphere.
The mysterious repeated infrasound signals were detected by the microbarometers along with the typical sounds of nature and human activity.
The sensors were launched into the air by balloons created by Bowman and his colleagues. Balloons were constructed from common and affordable materials and ranged from 20 to 23 feet (6 to 7 meters) in diameter. These seemingly simple machines could ascend to an altitude of about 70.000 feet (13,3 miles) above the Earth's surface when powered by sunlight.
According to Bowman, our balloons are essentially large plastic bags with some charcoal dust in them to give them a dark appearance. “We build them using charcoal dust purchased from pyrotechnic supply stores, packing tape, and painter's plastic from the hardware store. The air inside the shaded balloons heats up and gains buoyancy as the sun's rays hit them.
Balloons Powered by Solar Energy
According to Bowman, these solar energy balloons are enough to lift the balloons from the planet's surface into the stratosphere. The researchers had to use GPS to track the balloons after they were launched, because balloons often rise hundreds of kilometers and land in difficult-to-navigate parts of the world.
Also, as recent examples have shown, research balloons can occasionally be unintentionally mixed with other objects, causing panic.
Solar-powered balloons like this could be used to study mysteries even further from Earth, as well as aid in further investigation of these enigmatic stratospheric sounds.
Such instruments are currently being tested to see if they can be used with a Venus orbiter to probe seismic and volcanic activity in Venus' dense atmosphere. Robotic balloons can fly in the upper atmosphere of "Earth's evil twin", above its densely hot and pressurized surface, exploring its dense atmosphere and clouds of sulfuric acid.
At the 11th American Acoustic Society Meeting (opens in new tab) in Chicago on Thursday, May 184, Bowman will present the team's work on identifying these unidentified infrasound sources.
Günceleme: 12/05/2023 18:56