IEZA Model 101

The IEZA model is a 2-Dimensional framework used to describe the auditory environment of video games. Between 2003 and 2008 it was developed at the Utrecht School of the Arts by Sander Huiberts and Richard Van.
The IEZA model consists of non-diegetic sounds (Affect and Interface) and diegetic sounds (Zone and Effect).

Diegetic Side:
 
Effect:

• These sounds refer to the activity of the avatar/player (gunshots, footsteps, breathing etc) and events or sources within the diegetic part of the game.
• Effect generally responds to the player's activity in the diegetic part of the game environment but also contains sounds that are triggered by the game within the diegetic part which are not controlled or influenced by the player.
• Sounds belonging to this domain are often designed to react with the player in a way that refers to sounds in the real world, and are often dynamically processed using techniques such as real-time volume changes, panning, filtering and acoustics.

 Zone:

• Generally the 'Zone' domain in many games is often referred to as ambient, environmental or background noise. Such environments form a virtual representation of the environments found in the real world.
• When 'Zone' is compare to 'Effect', it is more often linked to off-screen sources, as one important property is that it's often designed and moulded to make the game world be perceived as 'bigger' than only the visual counterpart.
• Although 'Zone' if generally non-responsive and doesn't need player interaction, in certain instances the player can trigger a 'Zone', for example, in Grand Theft Auto 5 (2013), when the player is being chased by the police, other people nearby will be alerted and they might respond by shouting in fear and running away. Also when a player is being chased by the police, a background instrumental will kick in to match the mood of the gameplay.

The non-diegetic counterpart of the IEZA model can also be divided into 2 domains (Interface and Affect). 
Interface:

• The interface domain is the non-diegetic part of the game environment, player activity and also game events. This domain usually has sounds that are 'more abstract' and the sources of these activities are often designed using signs, for example, in Counter-Strike 1.6 (1999) when a player hits a button in front of a health pack, it will make a sound that there is still health to be extracted and when there is none left, another sound will play which indicates there is nothing left. Another example of this domain in use is in Resident Evil: Code Veronica (2000) when the player's inventory is pulled up, a sound (that certainly matches the mood of the game-where a zombie outbreak is taking place) plays when you are navigating through the different items.

Affect:

• The 'Affect' domain communicates the setting of the non-diegetic side of the game environment and is used to add or enlarge social, cultural and emotional references. Just like the 'Resident Evil' example that was given in the 'Interface' domain, where the sounds of the in-gae player inventory menu matches the situation of the gameplay. Another example of the 'Affect' domain can be seen again in Resident Evil: Code Veronica (2000), when the player enters a room where they are able to save the game and where no zombie can enter, a more relaxed - but still in this zombie outbreak - mood instrumental starts playing to accomodate the scenary/situation.
• A more accurate and better example of this domain in use is in Fifa '99 (1998), when the game is paused, popular songs will start playing (Fatboy Slim - The Rockafeller Skank) until the player unpauses and if paused again after, another song will play.