Unexplained Stratospheric Noises Detected by Solar Balloons
Researchers from Sandia National Laboratories in New Mexico have used solar-powered balloons to capture mysterious sounds in Earth's stratosphere, including thunder, ocean waves colliding, propeller aircraft, city sounds, suborbital rocket launches, earthquakes, and several unidentified noises. The balloons carried infrasound recorders up to 70,000 feet, and some of the mysterious infrasound signals occur a few times per hour during flights, but their source remains unknown.