Reverb zone
A volume in the scene that stamps the surrounding space's reverberation — a cave's echo, a bathroom's ring — onto every sound played inside it.
Walk into a cathedral and footsteps should suddenly echo; walk out and the echo should die. A reverb zone is the invisible box that handles it: sounds inside run through a reverb filter with a preset for the room, and the engine crossfades between zones at the boundary. The idea was standardised in hardware by EAX (Creative Labs, 1998) and I3DL2, which handed developers ready presets — "cave", "hall", "sewer". Today it is all done in software through FMOD or Wwise. It usually pairs with distance attenuation and occlusion to complete the sense of a room.