The Noisiest Places Are Found Far From the City

Researchers catalogue sounds of several varieties that exist beyond the perception of human hearing. This kind of research is intended to contribute to later discoveries about the noise in the world, but it also reveals plenty of surprises.

As an explainer post by Maggie Koerth-Baker describes, there's a lot to noise that humans don't perceive. "And when you start listening for the sounds we can’t hear, the loudest place in America can end up being right under your feet."

Scientists have tools that can detect these “silent” waves, and they’ve found a lot of noise happening all over the U.S. Those noises are made by the cracking of rocks deep in the Earth along natural fault lines and the splashing of whitecaps on the ocean. But they’re also made by our factories, power plants, mines and military.

To illustrate this point, Koerth-Baker cites the work of Omar Marcillo, staff scientist at Los Alamos National Laboratory, who "is trying to map these sources of small seismic signals in order to help other scientists track very small earthquakes that could help predict big, dangerous natural disasters."

To do that, Marcillo and his team used data collected over a decade by the U.S. National Seismic Network — 100 stations that track the movement of the ground all over the country. They combined that data with information about nearby industries to start figuring out which noises were likely human-made.

The result of that research is a map of seismic noise that reveals the noisiest places in the country to be located in the Great Plains of the Midwest.

But seismic sound isn't the only variety of noise we humans don't hear. There's also infrasound:

Infrasound travels through the air, just like the stuff we can hear does, but in this case, the molecular jiggles and vibrations are happening too slowly for our eardrums to convert them into information our brains understand. Infrasound can travel long distances and is often the unheard ripples set off by an audible sound that happened far, far away.

Scripps Institution of Oceanography researchers Catherine De Groot-Hedlin and Michael Hedlin are the researchers cited in this example.

 "In their data, it’s Western states like Nevada, Utah and Idaho that turn up loudest, probably the result of nearby military facilities."

The article also a map of the loudest places for infrasound.