Scientists are using sound to unlock the secrets of our planet

Wbird clash. The branches of the trees vibrate. The mosquitoes buzz. These phenomena happen every day, but not necessarily everyone hears about them. In fact, some sounds occur in places that are difficult for humans to access or below the level of what we can perceive. But increasingly, scientists are listening.

From a root system 90 feet underground, to balloons floating 70,000 feet above the ground, this week experts gathered at the Acoustical Society of America’s annual conference are showcasing a host of recent audible insights. New data revealed by these sounds is helping scientists better understand the natural world.

For example, last year researchers discovered that climate change is accelerating sound transmission in the ocean, with potential implications for marine life. More recently, in March, a study published in Nature revealed how the pandemic reduced the noise of shipping in the deep ocean, decreasing the amount of anthropogenic disturbance to the very soundscape of the marine environment on which animals depend. And this summer ecological plan monitor how remote Alaskan wildlife is responding to climate change and industry; they will do this by listening to the singing of birds and the buzzing of insects to analyze their abundance and activity patterns.

It’s a “chance to really hear a whole new world,” says Daniel Bowman, principal scientist at Sandia National Laboratories, a Department of Energy homeland security and technology laboratory, adding that this type of research provides “another perspective on sound from a different point of view”—in his case, miles above the ground.

A stratospheric symphony

In a layer of our atmosphere far above where commercial airliners fly, a group of scientists, including Bowman, have been launching balloons to record sounds that would not otherwise be heard in the relatively quiet region of our sky. Using low-frequency microbarometers, they were able to detect what the earth sounds like from so high up, from thunderstorms to wind turbines to freight trains.

In 19 days duration recording exhibited at the conference, a quiet, wind-like hiss can be heard, interspersed with crackles and pulsing. That hiss is the sound of waves crashing into each other in the middle of the ocean. “You’re listening to the ocean below, basically crashing into itself and making the signal travel up and past the balloon and actually heat the upper atmosphere as the sound wave dissipates,” Bowman explains. In other words, the recording measures how the ocean changes energy patterns 60 miles up into the sky. “There are all these really amazing things that happen,” he says. “It never really occurred to me that it was happening, and then with this new point of view, we can measure it directly.”

The investigations inflate a solar hot air balloon equipped with an infrasound microbarometer.

Darielle Dexheimer—Sandia National Laboratories

Bowman hopes to use his findings to inspire others, whether a high school science student or professional researchers, to perform similar experiments to better study this little explored region of our sky. The balloons he used in his project are cheap, use $50 worth of materials, and easy to build, and can be used not only to record acoustics but also for things like aerial photography or measuring greenhouse gases. (Her experiment of his is also part of a proof-of-concept with NASA to explore seismic activity on Venus.)

“It’s not like we’ve explored every nook and cranny in the stratosphere,” he says, “so it still has prizes in store for us.”

The sound of tree roots.

There may also be many new things to discover underground.

The largest tree in the world by weight and land mass lives in southern Utah. Known as Pando, the 9,000-year-old aspen forest is a unique organism made up of more than 47,000 genetically identical trees. As detailed in a conference presentation, the non-profit organization Friends of Pando used hydrophones, underwater microphones, to record what are believed to be vibrations transmitted along Pando’s root system during a thunderstorm. .

“It’s similar to two cans connected by a string. Except there are 47,000 cans connected by a huge root system,” Jeff Rice, a sound artist working with the nonprofit, said in a statement. The rustle of leaves in the wind caused the hydrophone to pick up signals underground: the more vigorously the leaves and branches waved, the stronger the signal.

“While it started as art, we see enormous potential for its use in science,” said Lance Oditt, executive director of the nonprofit organization. “Wind, converted into vibration (sound) and traveling through the root system, could also reveal the inner workings of Pando’s vast hidden hydraulic system in a non-destructive way.” The group hopes to use the data from these recordings to study water movement, insect colonies, and root depth, among other things.

That being said, the artistic interpretation of the sounds of nature is, in itself, another valuable way to make sense of the world we live in. For example, a percussion-based song was also showcased at the conference this week. interpretation of 120 years of oil extraction in the ocean. And the trend extends beyond the walls of the conference. An album by the British musician Cosmo Sheldrake released last month uses a cacophony of underwater recordings as the basis of its songs, from the song of humpback whales and the crackling of coral reefs to a rare recording of Britain’s last remaining orcas threatened by chemical pollution. Meanwhile, a group of graduate students at the University of California at Berkeley in 2018 turned more than a century of rising temperatures into a original musical composition.

Sound is a powerful sense. Rain and waves can calm us down. Sirens send us warnings. And just a snippet of a song’s chorus can bring back a lost memory. By unearthing sounds that were previously inaccessible, scientists now connect us more intimately than ever with the world around us. And by turning data into music, artists can help us experience potentially abstract science in a visceral new way. Together, this can force us to think and feel differently about the wonders of nature and our impact on the planet.

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