Operator stacks (in all games since ) can be used to define even more complex behaviours. Soundscripts contain 'sound entries' that are used to wrap Source-specific playback instructions around WAV or MP3 files.Ī sound entry can define the meaning of a sound to NPCs, its pitch and volume, how far away it can be heard from (attenuation), and can be used to randomise which precise sound file is played.