Every kind of soil sounds different. It depends on whether you are in the forest, on a field or somewhere in the city.
I came across this variety of sounds quite by chance. As a scientist and sound artist, I am interested in acoustic ecology. In my work, I make natural phenomena audible. Listening to things that you can't normally hear and use them to point out problematic connections. Climate change also makes sounds if you listen in the right place: alarm signals like the drought stress sounds of trees can be recorded acoustically. And after long dry periods, the whole landscape becomes silent.
Some time ago I was in Switzerland for a research project in the Valais. Out of pure curiosity, I stuck the sensor of my highly sensitive microphone into the ground of a meadow - and was completely fascinated. For days I stayed there listening as a completely unknown realm of strange sounds opened up to me: strange chirping sounds, a singing and humming. I had to know where the sounds were coming from. And I quickly realised that the “soundscape”, that is, the sound world of the ground, was still completely unexplored. That was the beginning of my research and art project “Sounding Soil”.
“Under intensively cultivated farmland, it is suddenly goes very quiet.”
In my recordings you can hear the meso to macro fauna, the medium to larger soil animals that live in the upper litter layer of the soil. This is an important functional group in the soil system because these soil animals are the primary decomposers. A healthy soil needs them. The soil animals move, they eat and they also talk to each other. The red garden ants, for example, make interesting noises with their upper jaw - it sounds like a squeak. For me, these communication sounds are the most fascinating part of my research. You also hear physical sounds, like water moving through the soil space or evaporating on the surface. And of course human noise: roads, construction sites and even airplane noise can be heard for kilometres underground.
I have made soil recordings in very different landscapes. Human management plays a big role, but also the type of ecosystem. You hear the most noise under meadows, because they have a thick organic layer where the activity of the soil animals is very high. The second most sounds are in forests. Then under intensively cultivated grassland and in last place is intensively cultivated farmland, because there it is suddenly very quiet. In cities, on the other hand, you can often hear a surprising amount. Even there, there are niches where the soil fauna is rich.
My research project consists of three parts: Scientifically, we prove that soil biodiversity can be measured acoustically. We relate the diversity of a recording to the actual biodiversity detected in soil samples. In the second, artistic part of the project, I develop sound installations from the soil recordings. And the third part is about raising awareness among the general public.
“The soil and animals move, they eat and they also talk to each other.”
It is important to make something as abstract as the effects of climate change or lack of soil health directly tangible. Because the sounds of the soil are not audible if you simply put your ear to the ground. They have to be amplified. But when you hear them, it creates a certain intimacy, things come closer to you. Environmental problems suddenly turn into a real experience. And that allows people to have a new relationship with their environment.