One of my favorite stories from the nonprofit I work at is about the city kid on his first trip into the wilderness, who kept telling one of our adult volunteers to “listen” for a noise he was hearing. After a few minutes, the adult figured out that the teenager had never heard the sound of silence before that experience. Gordon Hempton has taken it upon himself, over the past three decades, to get to those “quiet” places in nature and capture those sounds. “Soundtracker” is a profile of his quest, taking 20 trips a year in his VW van, capturing “sound portraits” with his business partner, Fritz, who is a human head-shaped microphone that Hempton can place on top of a boom or a tripod as he walks the earth looking for unique sounds that may be disappearing from our landscape, like a breeze blowing through a field of tall grass. In one scene, Hempton parks his van in an empty field, walks out of the van to listen and see if he can find a good sound to record, and is visibly irritated by the low hum coming from a power transformer. He says that sound, coming from computer fans, light sockets and everywhere else, is “the American mantra.” He might have a point.