Today, in a relatively new field known as soil bioacoustics – others prefer terms such as biotremology or soil ecoacoustics – a growing number of biologists are capturing underground noises to open a window into this complex and cryptic world. They"ve found that something as simple as a metal nail pushed into the dirt can become a sort of upside-down antenna if equipped with the right sensors. And the more researchers listen, the more it becomes apparent how much the ground below us is thrumming with life.