As game audio has become more popular and widespread several professionals and commentators involved in the gaming industry have tried to define the different elements which make up sound in games. Karen Collins in her new book Glossary of Game Audio Splits Game Audio into four groups within which are several sub groups;
Dynamic Audio is sound that reacts to changes in the gameplay, environment and input from the user. Within Dynamic Audio there is Adaptive Audio and Interactive Audio. Adaptive Audio is sound that occurs in the game environment reacting to the gameplay rather than input from the user. Interactive Audio is sound that is reacting to gameplay but is responding to the users input.
Diegetic Sounds are real sounds that occur within hearing distance of the user, this includes sound effects and dialogue. Non-Dynamic Diegetic audio is sound that occurs within hearing distance of the user but the user has no direct involvement in the sound. Adaptive Diegetic Audio is sound that reacts to changes in the environment but not the player directly. Interactive Diegetic sounds are sounds that occur in the players space that the player can directly interact with, these include footsteps and weapon impacts.
Non-Diegetic Sound refers to background music and sound effects. Adaptive Non-Diegetic sounds are sounds that occur in reaction to gameplay but aren't affected by the player and aren't part of the environment and cannot be heard by the game characters. Interactive Non-Diegetic Sounds are sounds that can be affected by gameplay or the player but cannot be heard by the game characters. This describes interactive music or sound effects reacting to gameplay. Non-Dynamic Linear sounds are sounds that are unaffected by the players input or gameplay, these sounds are usually found in uninteruptable cut scenes.
Kinetic Gestural interaction refers to Diegetic or Non-Diegetic sound which the player and typically character participate physically with the sound on screen. this can be as simple as using a controller to play an instrument on screen or using a Wii controller to control the velocity of weapons or perform actions that produce sounds.
Sander Huiberts and Richard Van Tol from GamaSutra.com take a simpler view splitting game sound into four parts Zone, Effect, Affect and Interface
Zone Refers to environmental sound, these sounds are diegetic and set the game ambience.
Effect refers to diegetic sounds during gameplay that are produced: ie footsteps, gunshots, explosions. these sounds can be on or off screen.
Affect refers to non-diegetic sounds that set the mood of the game, these range from orchestral music to moody low tones
Interface refers to non-deigetic sounds these can be menu sounds or sounds related to the HUD, the main use of these sounds is to convey information that isn't setting the mood.
These two examples both describe all the main types of game audio however i think that Karren Collins description is over complicated. There are too many sub sections and the descriptions of the sub sections are too diffuse. By having this many catagories i find that i cannot get some audio to sit in any one catagory, weather this is due to the language used in the description or just my mistake. GamaSutra's IEZA framework is a much better breakdown of game audio types because it is simple, complex audio can easily be divded into the different catogories. I have found some examples of the four major groups from GamaSutra's IEZA framework.
Zone This clip shows some ambient passes of Unreal Tournament 3 each level has a different feel because of the change in the background sounds used.
Effect This clip shows a short clip of Call of Duty 4 it features allot of diegetic sound effects from weapons, enemies and the plane this makes it to be a very immersive realistic experience. Affect This F.E.A.R clip is a good example of how Non-Diegetic sounds can affect the feel and mood this game in particular relies on discordant sounds and stabs throughout to make the game allot scarier.
Interface This Metal Gear Solid 4 Clip has some good examples of information sounds via the HUD and the radio menu. for example when Snake enters the radio and also when he is flicking through the inventory.