The Never-Heard-Before Sound of Earth’s Rumble

earth south pole north pole equator

Chances are you never give a second thought to one of life’s essentials: Earth’s magnetic field.

We almost never think about the magnetic field — but our lives depend upon it. It extends several tens of thousands of kilometers into space and saves the Earth from becoming the sun’s frying pan by protecting Earth (and our ozone layer) from the charged particles of solar wind and cosmic rays.

The Aurora Borealis offers a visual display of charged particles from the sun interacting with Earth’s magnetic field, but most observers are too taken up with the colors to appreciate the magnetic field behind it. Because it is so important, the European Space Agency used its SWARM satellite mission to measure these important magnetic signals.

Then scientists at the Danish Technical University (DTU) took the magnetic signals measured by ESA’s mission (and other sources) and converted them into sound — and last month broadcast the rumble of Earth’s magnetic field to the public via 32 loudspeakers dug into the ground at the Solbjerg Square in Copenhagen, Denmark.

These sounds of Earth’s magnetic field have been called “five minutes of haunting, crackling audio.”

“The rumbling of Earth’s magnetic field is accompanied by a representation of a geomagnetic storm that resulted from a solar flare on 3 November 2011, and indeed it sounds pretty scary,” says Klaus Nielsen, project coordinator at DTU.

“We gained access to a very interesting sound system consisting of over 30 loudspeakers dug into the ground at the Solbjerg Square in Copenhagen,” explained Nielsen.

Klaus Nielsen

Klaus Nielsen, project coordinator at the Danish Technical University (DTU)

Thirty-two Soundwell speakers are permanently fixed into the ground of this public square and hooked up to a 32-channel sound system. Every week they play a different soundscape but in late October (hey, it’s Halloween time!) the DTU treated unsuspecting people traversing the square to the first public concert of Earth rumbles.

rAVe Europe talked to Nielsen about the project.

“The method used is called Data Mapping. This means data is not transformed into sound but instead used to control sound — rather like a musical score.

“Data was taken from a model of the Earth’s magnetic field called GGF100k, which is a Global Geomagnetic model of the core field going back 100.000 years.

“We chose 32 points on the globe corresponding to the location of each speaker on the square and extracted 32 time series in CSV format.

solbjerg square

“Each time series was resampled to give a 1 data point per 100-year resolution.

“The biggest challenge was converting the CSV files into messages that can be understood by musical software. Using the free musical software VCV rack — and the plugin module Data Sonification we were able to convert the data points into midi cc messages.

“We chose to convert the data points as pitch wheel messages to retain as high a resolution as possible.

“The converted data time series were then used to control different musical parameters (volume, pitch, filter) on a set of samplers playing back sounds of rocks moving, wood breaking and other rumbling sonic oddities.

“In addition, data from a solar flare event from 3 November 2021 was given a similar treatment and mixed in with the core field as an extra sonic layer in the higher frequency area.

“The result was 32 wav files of 5 minutes each distributed to the 32 speakers.”

The ESA reminds us, “The intention, of course, is not to frighten people — it is a quirky way of reminding us that the magnetic field exists and although its rumble is a little unnerving, the existence of life on Earth is dependent on it.”

For more info on Soundwells:

The video from DTU:

Read ESA’s news story:

Hear audio only: