For the first time in half a century, strange sounds were recorded by scientists on the border of the stratosphere and space. Researchers have not yet been able to figure out the origin of the noise. However, the intensity and complexity of the infrasonic signals are striking. Researchers are preparing for new experiments.
The strange sounds were recorded using equipment developed by University of North Carolina graduate student Daniel Bowman as part of a project for NASA. During the experiment, special microphones were lifted into the upper atmosphere on a balloon inflated with helium. It rose to a height of 37.5 thousand meters. This is much higher than the mark at which airplanes fly, but at the same time, below the point where the border between open space and the upper layers of the stratosphere lies.
As a result, the instruments detected whistles and hiss at a frequency of less than 20 hertz. The signals are indistinguishable to the human ear, and the recording from a special microphone has to be accelerated to hear mysterious sounds.
“It's kind of like the X-Files,” Bowman said, adding that he was shocked by the intensity and versatility of the signal.
The source of these strange sounds remains a mystery to scientists. On this score, there are many guesses and assumptions. For example, some believe that it is echoes of ocean waves, gravitational waves, air turbulence and turbulence, even the interference from the cable of the helium balloon itself, which lifted the recording equipment into the air. Natural phenomena such as storms and earthquakes can also generate such sounds.
Despite the fact that the exact source of low-frequency signals has not yet been established, the experiment has already been recognized as a great success. For the first time in 50 years, acoustic recording has been done in the stratosphere, Bowman says. Scientists are already preparing for a new experiment to take place this summer.