One of the biggest challenges faced by the Sound Designer and Audio Programmer when implementing sounds into a game is the issue of sound repetition. In the real world (excluding artificial systems like a fire alarm which convey information) you would not expect to hear the exact same sound twice. For example hearing the exact same dog bark three times in a row would probably be most unsettling and you would start to question whether you were actually in real life or in-fact part of some artificially created world that was experiencing a minor glitch.
Provided we are talking about non-symbolic sounds (which carry meaning or convey information), the same is true for computer games. If a player experiences something that is particularly unnatural or breaks the ‘flow’ 1 of the game then they will pulled from the game environment as their attention is drawn to this event, breaking any immersion built by the game so far 2. Immersion is seen as the Holy Grail of the gaming experience and therefore it is the challenge of the game audio team to overcome these obstacles within the technical limitations posed by the game platform.
With the increase in system resources that have come from improvements in technology, various systems have been developed to deal with the issue of sound repetition in games, two of the most commonly used systems are explored below:
·
Pitch
Shifting and volume modulation can
be used to increase variation in
one-shot sounds and layered textures. When applied subtly and randomly, using
modest values, a large range of variation can be achieved with only a few sound
files giving savings on both time and memory, which is always a good thing! This
technique typically works best on repetitive sounds like footsteps or gunshots
but can equally be applied to layers of atmospheric textures such as bird song.
·
Horizontal
Concatenation, which involves
combining several small sound files to create a longer sound, is frequently
used to provide variation in ‘one-shot’ sounds. When this process is randomised,
this allows for a huge number of variations from only a few original sounds
(the actual number of permutations is '(2x) - 1' where x is the number of
sound files used.). A simple concatenation system from UDK is shown below:
The boxes to the right side of the of the system are the sound files which will be combined to create the overall longer sound. These are combined at random using the 'Random' object and then passed to the 'Concatenator' object where they will be 'stitched' back together in a top down order.
The video below demonstrates an example of non-repetitive sound design in the latest of the ‘Elder Scrolls’ series of games, Skyrim.
As you can hear, each time the bow is fired, a different set of sounds is heard. This is relatively close to what you would expect to happen in real life and thus does not draw attention to the action and break the 'flow' of the game. Obviously I can only speculate about the methods actually used to implement this system but for the purposes of this analysis I will assume that they have used the methods I have covered above. Sonically it appears that the firing mechanic of the bow is split into four distinct stages.
Once these stages are established the various recorded or premade bow sounds can be edited and divided among the four groups. A system much like the basic concatenation system shown above could then be implemented to randomly splice the samples together in the correct order. Pitch and volume modulation could be applied to each of the stages to provide further variation.
References:
- Chen, Jenova. “Flow in Games (and Everything Else).” Communications of the ACM 50, no. 4 (April 2007): 31–34. - Great paper on the 'flow' theory in games.
- Stevens, Richard, and Dave Raybould. The Game Audio Tutorial: A Practical Guide to Sound and Music for Interactive Games / Richard Stevens, Dave Raybould. Amsterdam ; Boston : Focal Press/Elsevier, c2011., 2011. - Excellent book on all things game sound related
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