They Detect Mysterious Sounds In Earth’s Stratosphere And Scientists Don’t Know What It Is

A team of researchers from Sandia National Laboratories (SNL) in New Mexico, directed by Daniel Bowman, They discovered low-frequency sounds in the second layer of the Earth’s atmosphere that cannot be attributed to a known source.

The mission was carried out by solar-powered hot air balloons that soared more than 20 kilometers into the sky to reach the stratosphere, a relatively calm layer of Earth and rarely disturbed by aircraft or turbulence.

THE microphones in the stratosphere can pick up sounds not heard elsewhere, like the natural sounds of ocean waves and crashing thunder, or man-made sounds like wind turbines or explosions, and even sounds of unknown origin, he explains. A declaration.

“When we first started flying balloons years ago, we didn’t really know what we were going to hear,” says SNL’s Daniel Bowman, as reported by New scientist. “We learned to identify the sounds of explosions, meteorites, airplanes, electrical storms and cities. But pretty much every time we send balls out, we find sounds that we can’t identify.” adds.

To collect the data, Bowman and his collaborators they built balloons between six and seven meters wide, with ordinary materials. In fact, for each balloon, they only needed about 40,000 Chilean pesos (US$50).

“Our balloons are basically giant plastic bags with charcoal dust inside to darken them. We built them using painter’s plastic from the hardware store, masking tape, and charcoal dust from pyrotechnic supply stores. When the sun shines on the dark balloons, the air inside heats up and becomes buoyant. This passive solar power is enough to take the balloons from the surface more than 20 km into the sky,” Bowman said in the statement.

They started with their first balloon release in 2016 . The researchers sent 50 balloons into the sky to sample the rumblings of the stratosphere and initially set out to record the sounds of volcanic eruptions.

But then he and his adviser Jonathan Lees of the University of North Carolina at Chapel Hill realized that “No one had tried to bug stratospheric balloons in half a century, so we continued to explore what this new platform could do” Bowman explained to CNN.

They installed microbarometers inside the balloon, capable of detecting low-frequency sounds, and measured infrasonic signals, that is, sounds with a frequency of 20 hertz (Hz) or less, which are inaudible to the human ear.

Once released, they plotted their routes with the GPS, Because as they traveled hundreds of miles, upon landing they had to find the exact location where they needed to review the data.

It was during these flights that the researchers recorded persistent low-frequency sounds, the origin of which they could not identify. Scientists have several theories about the origin of these mysterious noises, ranging from possible previously unrecorded forms of atmospheric turbulence to distorted echoes from the ground that are unrecognizable.

“[En la estratosfera,] There are mysterious infrasound signals occurring several times per hour on some flights, but the source of these is completely unknown.” Bowman said in the release.

Because balloons are cheap and easy to build and launch, they could be used not only to further study these mysterious sounds in the stratosphere, but far beyond Earth.

In particular, Bowman collaborates with the JAR develop similar technology to explore the atmosphere of venus and analyze its seismic and volcanic activity. Since Venus’ atmosphere is very dense and hot, robotic balloons could be a valuable tool for obtaining information that would otherwise be inaccessible.

The findings were shared by Bowman on Thursday at the 184th meeting of the Acoustical Society of America in Chicago.