The sound comes from Half-Life 2, the first-person shooter released by Valve in 2004 and built on the Source engine. Its doors in City 17, laboratories and Combine facilities use short mechanical effects like this one to sell weight and technology without animation alone. The clip later spread through Garry's Mod, Source Filmmaker and machinima, where creators reuse the same audio for custom maps and videos. That reuse keeps the door instantly recognizable to PC gaming fans nearly two decades later.