Hear the Otherworldly Sounds of Skating on Thin Ice | National Geographic

This small lake outside Stockholm, Sweden, emits otherworldly sounds as Mårten Ajne skates over its precariously thin, black ice. “Wild ice skating,” or “Nordic skating,” is both an art and a science. A skater seeks out the thinnest, most pristine black ice possible—both for its smoothness, and for its high-pitched, laser-like sounds