NASA records mysterious sounds 36 km above Earth's surface
Click to Hear The sound was recorded by a UNC Chapel Hill payload aboard a high altitude balloon. The balloon was commissioned by Louisiana State University's High Altitude Student Platform (HASP) program and flew to an altitude of ~22 miles in 2014 A NASA high-altitude balloon experiment run by graduate students in the US has captured some unexplained and strangely complex sounds at 36 km (22 miles) above the surface of Earth. Known as atmospheric infrasound, these sound waves dip below frequencies of 20 hertz, which is beyond the range of human hearing.