Low frequency sounds can travel vast distances across our planet, carrying information about the events that generated them as well as the medium through which they travel. These sounds are usually recorded on surface-based sensors. Recently, however, sensors have been lofted on high altitude balloons, where they have revealed a rich soundscape quite different than that of the Earth’s surface. Using inexpensive microbarometers lofted via passive solar hot air balloons, Sandia National Laboratories researcher Daniel Bowman and his colleagues detected background noise as well as individual infrasound events, some of whose origins remain enigmatic, in the lower stratosphere of our planet.
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