Mysterious hisses and whistles have been recorded 22 miles above the earth’s surface using infrared microphones aboard a Nasa student balloon experiment. The ‘infrasounds’ were captured by Daniel Bowman, a student at the University of North Carolina, according to a report in LiveScience.
The sounds can only be heard by human ears after speeding up the recordings and were picked up at frequencies below 20 hertz. Listen :
‘It sounds kind of like The X-Files,’ Mr Bowman told Live Science.