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.
 



Explosion_Baked


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’

 



Explosion_Components


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’

[tweet_box]Why Procedural Game Sound Design is so useful – demonstrated in the Unreal Engine:[/tweet_box]



Explosion_Delays_and_Modulations


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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    This library contains multiple recordings of two antique Trench Rammers, the Pegson ER5 and the Warsop Benjo, and also features additional recordings of four antique stationary engines, the Amanco Hired Man (1920s), the JAP 1947, the Lister D (1940s) and the Norman T3000.

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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.

 



Explosion_Materials


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

 



Explosion Spatialized


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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  • Cinematic & Trailer Sound Effects Abandoned Oil Tank Play Track 327 sounds included $40

    On a recording trip to the smaller Danish port town Struer, I came across an abandoned empty oil tank. Inside I found two giant wires attached to the floor and the ceiling of the tank, almost like a huge 2 stringed double bass. I’m telling you the reverb in there was longer than the Eiffel Tower on a cloudless day !

    On the outside this was just an empty abandoned building, but it turned out it was not empty at all because it was full of sound and a few dead birds. I’m glad I was curious enough to go inside for a closer investigation and not just pass by.

    After several hours of concentrated recording, it was nice to get my ears back out in dry air. I’m happy there are no open sends to Valhalla in real life but experiencing the eternal resonance on the low frequencies from the wires was absolutely amazing.

    Abandoned Oil Tank was recorded with a LOM basic Ucho stereo pair, a Zoom H6 and the LOM Geofon. All files are in 96 kHz/24 bit and contain the original recordings.

    The result is a unique sound effect library including balloon pop impulse responses from a truly unique location that very recently became even more unique since word says that the oil tank is no more and has abandoned this world.

    327 individual sounds – all tagged with Universal Category System (UCS) metadata.

    www.katrineamsler.com

    20 %
    OFF
    Ends 1713131999
  • Electricity Sound Effects Polarity Play Track 975 sounds included $72

    Polarity delivers more than 950 sounds of electricity, science and technology – captured in several locations around the world, from electricity museums to science labs. About 50% of the library is all about electricity, with various types of Jacob’s Ladders, Tesla Coils, Ruhmkorff lamp and all sorts of impactful bursts of energy.

    Then we go through welders, plasma spheres, 3D printers, starting to cover a more broad technology theme – like old phones, telegraphs, dynamo wheels, rotary dials, whirling watchers, alarm, lab centrifuges, something scientists call a roller and a rocker, servo sounds, neon lights, a wimshurst machine and sparklers.

    Many sounds in this section were captured from vintage equipment, from a 1928’s tram to old telephone switchboards, high voltage levers and control surfaces.

    All content was recorded at 192KHz with a Sanken CO100K, a couple of Sennheiser 8040 and a Neumann 81i, translating into final assets that have plenty of ultrasonic content, ready for the most extreme manipulation.

    Bonus: Two extra libraries included for free:
    This library also includes two additional releases from Mattia Cellotto - for free: Crunch Mode delivers 230 crunchy sounds made with a variety of vegetables, fresh bread, pizza crust and a selection of frozen goods. The Borax Experiment gets you 158 squishy, gory, slimy and gooey sounds.
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    OFF
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