Ambience is the bed of background sound that defines a location's character -- chirping crickets, distant traffic, wind through trees, the hum of a spaceship, dripping water in a cave. Good ambience design layers multiple elements: a base tone (the fundamental hum of the space), random one-shots (a bird call, a distant door slam), and environmental loops (wind, water, machinery). These layers work together to create a sense of place that players absorb subconsciously. The best ambience reacts to game state -- rain starting, time of day changing, or danger approaching can all subtly shift the background soundscape.