The first time that Marcus Maeder stuck a noise sensor into the ground, it was on a whim. A sound artist and acoustic ecologist, he was sitting in a mountain meadow and pushed a special microphone he’d built into the soil. “I was just curious,” says Maeder, who is working on a dissertation on the sounds of biodiversity at the Swiss Federal Institute of Technology in Zürich.

He certainly wasn’t prepared for the clamor of sounds that started to flood his headset. “They were very strange. There was thrumming and chirring and scraping. You need a whole new vocabulary to describe it.” Maeder was eavesdropping, he realized, on creatures that live in the soil.

Ecologists have long known that the ground beneath our feet is home to more life, and more diverse life, than almost any other place […]