Their microphones recorded eerie mysterious sounds. giant solar balloons which were sent for research purposes to a height 21 km in the stratosphere.

According to NASA, the stratosphere is the second layer of the Earth’s atmosphere, and its lower level includes the ozone layer, which absorbs and scatters the sun’s ultraviolet radiation.

Daniel Bowman, Chief Scientist at the Sandia National Laboratory in New Mexico, has been committed to researching soundscape of the stratosphere when he came into contact with the low frequency sounds emitted by volcanoes. It is about the so-called infrasound (infrasound), the muffled roar they produce tsunamis, storms, earthquakes, volcanic eruptions, avalanches which are not perceived by the human ear.

Bowman and his friends originally attached cameras to weather balloons to take “photos of dark skies and Earth,” so they developed their own solar balloon.

Bowman suggested installing infrasound recorders to record the “roar” of volcanoes. It was then that he and his adviser Jonathan Lylas of the University of North Carolina realized that “nobody had tried to put microphones on stratostats in half a century,” so they decided to explore the possibilities of these new sensors, which could be flown at twice the height of a commercial aircraft.

“In our solar balloons, we recorded chemical explosions on the surface and underground, lightning, the roar of ocean waves, propeller planes, the sounds of cities, suborbital rocket launches, earthquakes, possibly trains and planes. We also recorded sounds of unknown originBowman notes.

The findings of scientists have been described in 184th American Acoustic Society Conference in Chicago.

The footage Bowman shared of a NASA balloon circling Antarctica contains echoes of crashing ocean waves (sounds like continuous breathing). But other sounds, such as clicks and rustles, have baffled scientists as they cannot pinpoint their source.

Between 2026 and last month, his team launched dozens of solar balloons (equipped with microbarometers) to collect infrasound recordings, Bowman said.

Source: CNN