procedural game audio Asbjoern Andersen


How do you keep your game audio varied – without needing countless individual audio files? Procedural sound design can help with exactly that, and in this hands-on guide, senior lecturer, teacher fellow and author of the Game Audio Implementation book, Richard Stevens, demonstrates how the concept works in the Unreal Engine.

When creating a sound effect for a movie you’ll know that the audience is only going to hear it on one specific occasion, and you’ll likely build it up through editing and layering different sound elements to get just what you want.

01_game_audio_Explosion

Figure 01 ‘An explosion’

 

Most games, like sports, are about skill and mastery, so the player will be repeating similar actions again and again, and consequently they will be hearing the same sounds again and again. The trouble is that we’re very sensitive to this kind of repetition, since it just doesn’t happen in real life.
 


http://www.vimeo.com/148925241

Video: Explosion Baked


 
The obvious answer is just to have loads and loads of sounds but it would be far too much work to create 30-40 versions of every sound in the game (plus there are obviously limitations as to how much we can fit on a disk!).
If we look at our ‘explosion’ sound again we can see that the final sound is made up of different characteristic components, and this idea is key to starting to think about procedural approaches to sound design.

02_game_audio_Explosion_Components

Figure 02 ‘Explosion Components’

What we want to do is to keep these components separate when we import them into a game so that we can recombine them in different ways at run time. A lot of sounds in games aren’t ‘sounds’ at all, they are systems of sounds. This kind of procedural approach requires a different way of thinking, and sometimes different kinds of sound assets, since we often want to isolate the individual components that make up a sound.

When we bring these components into a Sound Cue in the Unreal Engine we can build a system of playback, and by having a few different versions of each component we can randomly combine them to create variation.

03_game_audio_Procedural_Explosion

Figure 03 ‘Procedural Explosion’

 

http://www.vimeo.com/148779195

Video: Explosion Components


 
By taking this approach we don’t need thousands of complete sounds in our game to be able to get thousands of different sounds out of the system. Randomizing the combinations of layers can vastly increase the number of potential outcomes with only a few additional sounds.

By taking this approach we don’t need thousands of complete sounds in our game to be able to get thousands of different sounds out of the system

In the above example we have four sets of three possible sounds that can potentially be heard so this will give us 81different sound outcomes. If we added just one other ‘Crack’ element then we’d get 108 potential sounds.


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We can increase this variation even more by adding some slight randomized delays and modulations of pitch and volume to each element, giving us.. erm… a very large number of possible outputs.

04_game_audio_Delay_Mod

Figure 04 ‘Adding Delay and Modulation nodes’


http://www.vimeo.com/148779193

Video: Explosion Delays and Modulation


 

Another thing we might want to do is to change the sound depending on what was being blown up, or the materials of nearby objects. Again by keeping these material components separate we can choose to layer them into the Sound Cue when appropriate by using a switch.
 


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By getting information from the game about what type of material is being blown up we can use this to control the switch, and therefore which material components of sound get added to the overall explosion sound.

05_game_audio_Explosion_Materials

Figure 05 ‘Explosion Materials’

Thoughts on the term ‘Procedural Sound Design’:

In writing the book we made a conscious decision to term this kind of sound design, that is typical in the current practice of game audio, ‘Procedural Sound Design’ to differentiate it from ‘Procedural Audio’.

Andy Farnell, who coined or at least popularised the term ‘Procedural Audio’ sees it as any kind of system where the sound produced is the result of a process. He describes these ideas more fully here. So under that definition, as soon as you set up any kind of system of playback you could see it as being procedural audio.

However there has been a lot of important work and progress in terms of procedural audio for games in the last few years (see http://proceduralaudionow.com/), and this has encompassed a variety of techniques, but there has been some emphasis on the idea of these procedural systems being synthesis based, which ultimately is probably the most flexible solution for interactivity.

This is a specialist field which we don’t go into in any depth in the book since there are other great books out there on this (not least Andy’s book ‘Designing Sound’). In the book we attempt to describe the range of procedural approaches by saying, “This approach to sound design exists on a spectrum from procedural sound design, where we tend to be manipulating pre-existing assets, to procedural audio, a term more frequently used when systems of synthesis are used to generate the sounds themselves (with much in between that combine both approaches)”.

To throw another thing into the discussion, when discussing music systems we also use the term algorithmic, which again could be used to describe any kind of system of playback. Although we could just call this procedural music (as others such as Karen Collins have done), but we felt it worth preserving and highlighting ‘algorithmic’ given the long history of algorithmic techniques explored for music in the past, which a search for ‘procedural music’ is going to miss.

 


http://www.vimeo.com/148779198

Video: Explosion Materials


 

Now we have all the elements of a sound as separate components we can also do other things with them, like spatialize them around the player in different ways. For the Game Audio Implementation book we built a simple system that will throw sounds around the player for people listening in 5.1 or 7.1. This could be used for elements of the explosion itself or for debris.

06_game_audio_Spatialized_Diagram

Figure 06 Diagram

 

07_game_audio_Spatialized_Detail

Figure 07 Detail

 

This was done in Unreal’s Blueprint system – which looks a bit daunting at first but once you get the hang of it you can pretty much do anything you might dream up!

08_game_audio_Blueprint

Figure 08 Blueprint

 


http://www.vimeo.com/148779197

Video: Explosion Spatialized


 
By using a procedural approach to sound design we now have an explosion sound that’s different each time, is ‘aware’ of the different materials involved in the explosion, and spatializes around the player in stereo, 5.1 or 7.1.
 

A big thanks to Richard Stevens for his insights on procedural game audio! If you want to know more about procedural sound design for games then check out the Game Audio Implementation book from Focal Press. If you’re new to UE4 you can get UE4 here for free, and you can download all the levels that go alongside the book here (also for free!) to get started.
 

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    Animal Sounds $25
    Explosion Sound Pack $10
    Footstep and Foley Sounds $10
    Fun Casual Sounds $15
    Fun Character Voices $10
    Gun Sound Pack $19
    Guns, Bullets and Explosions $35
    Human Vocalizations $25
    Magic and Spell Sounds $25
    Punch and Combat Sounds $29
    Retro 8 Bit Sounds $15
    Sci-Fi Sounds and Sci-Fi Weapons $25
    Silenced Gun Sounds $25
    Troll Monster Vocalizations $10

    Total value $278!!!

    Sound Categories:

    • Alarms • Ambience • Animals • Beeps • Bullets • Buttons • Cartoon • Cinematic • Collectibles • Comedy • Doors • Electricity • Explosions • Fire • Foley • Footsteps • Guns • Hums • Items • Levers • Magic • Misc. • Nature • Powerups • Punches • Retro/8Bit • Sci-Fi • Snow / Ice • Switches • User Interface • Voice • Water • Weapons • Whooshes + MANY MORE!

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    Snow & Ice is an extensive collection of various ice and snow sounds recorded in quiet rural locations in Northern Finland between 2015-2017. The library contains 1700+ sounds / 2.9 GB worth of material recorded and mastered in 96KHz 24bit quality, so they are more than ready for pitch shifting and other heavy audio processing.

    Among the biggest highlights of this library are the industry’s first glassy yet heavier sounding ice lantern breaks which will definitely be useful in adding unique twist to your material sound design. The library also comes with a huge variety of snow and ice debris sounds, snow block breaks and even footsteps on frozen snow and ice debris.

    You get the sounds in two formats: 96 kHz, 24 bit and in 44.1 KHz, 16 bit, for more convenient ways of utilizing the sounds in games and other media.

    FOOTSTEPS:

    Frozen Snow Packed Run • Frozen Snow Packed Scuffs • Frozen Snow Packed Stomps • Frozen Snow Packed Walk • Frozen Snow Road Walk • Frozen Snow Run • Frozen Snow Walk • Frozen Wood Terrace Walk • Frozen Ice Shard Debris Scuffs • Frozen Ice Shard Debris Stomps • Frozen Ice Shard Debris Walk

    ICE:

    Ice Debris Fall • Ice Debris Rattle Continuous Loop • Ice Debris Rattle Heavy • Ice Debris Rattle Light • Ice Debris Smash To Ground Heavy • Ice Debris Smash To Ground Light • Ice Lantern Collision • Ice Lantern Large Break Smash • Ice Lantern Small Break Smash • Ice Shard Break Smash • Ice Shard Crack Snap • Ice Shard Small Group Rattle • Ice Shard Small Hit Collision Rattle • Ice Shard Small Rattle

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