Sarah Sherlock

Procedural Sound Design. An Introduction

This blog post discusses  ‘Procedural Audio’ and  the use of ‘Procedural Sound Design’ in video games.

‘Procedural Audio’ is a term first popularised by Andy Farnell, where sounds produced are the result of a process ie: using a system to synthesise notes themselves using software such as Max to generate sound of purely digital tones. This type of Procedural audio does not require pre-recorded sound effects and allows the sound designer to use the audio engine to randomise variables such as: pitch, wave type, note length, vibrato, distortion, and various filters.

In relation to game audio the term Procedural Sound Design (or PSD) is used to describe a system  set in place where sounds triggered are comprised of  multiple elements and layers. R. Stevens refers to procedural sound design as a system, an algorithm, or a procedure that re-arranges, combines, or manipulated sound assets so they might:

• a. Produce a greater variety of outcomes
• b. Be more responsive to interaction

When we think of a typical sound effect that needs variation such as footsteps on different terrain this can be easily implemented using a random generator of sound files to be triggered when a player walks. However, for more environmental sounds that react within the sonic world of a game, these can be broken down to their core elements and layered at random. Much like when sounds are created using synthesis, if we consider the ADSR of a particular sound (attack, decay, sustain, release) such as an Explosion being comprised of an initial crack, followed by a boom and reverberant tail, by layering these sounds and setting up a system that randomises playback we create a much more realistic and immersive game experience.

Paul Weir, In speaking about procedural sound and his work on No Mans Sky Weir defines PSD as ‘it involves real-time synthesis that is live and interactive, controlled by data coming back from the game systems. According to the suggested definition above, this only makes sense if it solves a problem for you that would otherwise be difficult to resolve using conventional sound design’

So under these definitions, as soon as you set up any kind of system of playback you could see it as being procedural audio. In video game sound design, by controlling the repetition, randomisation and frequencies of sounds which are crucial to the quality of game audio, this aims to combat player ‘listener fatigue’ which refers to a phenomenon that occurs after prolonged exposure to an auditory stimulus.

Examples of Procedural Sound Design in Games

No Mans Sky (2016, Hello Games) a game that was created using many random variables on the generative and procedural approach to game design, sound designer Paul Weir created a system called Vocalien, a real time synthesis plug inside the game that results in an always different voice for each creature and doesn’t impact the memory of the game. Weir states that the advantage of this approach is that you can relatively easily construct an expandable infrastructure into which you can add layers of sound design that respond to the game state of environment.

Paul Weir demonstrates Vocalien on an iPad

Creature sounds in No Mans Sky

Heavenly Sword ( 2007, Sony) An example of a game where the procedural approach to sound design would result in more memory. Individual Sword Whooses and dialogue sounds recorded with change in reverb lengths. Now we can create systems to trigger the sounds and don’t require so many assists.

GTA: V (2013, Rockstar Games) Footsteps, Gunshots, Impacts

Conclusion

In most games we are sensitive to the repetitions that are not in real life. The obvious answer is 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. The procedural approach to sound design in games is effective for the following reasons: memory constraints of the game, when there is too much content to create and need variations of the same sounds.When the sound changes depending on the game context (environment)

Some procedural sound design models can be implemented very easily:

• Footsteps
• Impacts
• Air / Water / Wind

Here is an example of a computer sound made of individual one shots that loops within itself at random every time it is triggered in the game. By creating a loopaple sound system in Unreal Engine 4 this gives the sound designer a lot of advantages compared to just creating static sounds, repeatable loops or large files using mass amount of in game memory. Systems like these can now add to the soundscape of an in game environment, that feels dynamic and believable, causing the player to achieve complete immersion

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References

• Asbjoern, A. 2016, Why Procedural Game Sound Design is so useful. (A Sound Effect) asoundeffect.com
• Farnell, Andy. 2008, Designing Sound, The MIT Press
• Grand Theft Auto V, 2013, Rockstar Games
• Heavenly Sword, 2007, Sony Computer Entertainment
• Mongeau, A.S 2017, Behind the sound of ‘No Mans Sky’: A Q&A with Paul Weir (Audiokinetic Blog)  audiokinetic.com 
• No Mans Sky, 2016 ,Hello Games
• Stevens, R & Raybould, D 2015 (The Game Audio Tutorial: A Practical Guide to Sound and Music for Interactive Games)