The University of North Carolina Chapel Hill's 2014 High Altitude Student Platform (HASP) mission placed infrasound (below audible frequency sound) microphones 22 miles above the Earth in order to quantify the acoustic wavefield of the stratosphere-the first time this has been done in half a century. The microphones captured a variety of signals of unknown origin. Preliminary work indicates that the signals may originate from clear air turbulence, aircraft, wind farms, ocean waves, and cable vibrations on the balloon, but more investigation is required before definitive sources can be identified. The sound files featured here have been sped up by 100 times to bring the signals into audible range.
The HASP flight program is supported by the NASA Balloon Program Office (BPO) and the Louisiana Space Consortium (LaSPACE). Currently, HASP flies once a year in September from the Columbia Scientific Balloon Facility (CSBF) base in Fort Sumner, New Mexico.
Credit: HASP; UNC Chapel Hill/Department of Geological Sciences; Boise State University
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