Distance attenuation
Sound growing fainter the farther its source is from the listener — physically by the inverse-square law, in games by a tunable curve.
Physics says inverse square: double the distance, quarter the power, roughly −6 dB. Games rarely obey that literally, because a strict curve makes sounds inaudible far too quickly. Instead each source gets a rolloff curve with a minimum distance (full volume inside it) and a maximum distance (silent, or clamped, beyond it) — linear, logarithmic or hand-drawn. The right curve decides whether an explosion reads as close or distant. Together with HRTF for direction and occlusion for obstacles, it builds a spatial soundscape. Nearly every audio engine, from FMOD to built-in engine systems, exposes the curve straight to the sound designer.