How To: Make racing car engines roar using AudioMotors Fmod

Firelight Technologies and AudioGaming recently announced the integration of AudioMotors Fmod in the rally racing game WRC5.

Embedded in Fmod Studio, AudioMotors creates real-life engine roaring sounds for improved audio immersion.

Here, AudioGaming’s Amaury La Burthe runs through the steps you can take within Fmod Studio to implement AudioMotors within your racing game to take advantage of procedurally-generated engine noise.

Then, he breaks down the differences between the traditional method of creating engine sound audio and adopting a procedural approach.

AudioMotors FMOD Quick Start Quide

Step 1: Create a new event

Step 2: Add AudioMotors plugin

Step 3: Adjust the event duration for AudioMotors

Step 4: Try automation

Step 5: Play with automation

TRADITIONAL METHOD: ENGINE SOUND LOOP EDITING

The traditional approach to engine sound design is based on several engine sound loops of fixed RPM. Sound designers usually spend hours of editing work to find loop points for best crossfade and to fine-tune pitch-shifting for best RPM transitions. 

Downsides:

• Loop editing is time-consuming 
• Compromised quality due to pitch-shifting: since the CPU resource is limited on game consoles, the real-time pitch-shifting algorithm is usually simplified. Therefore, quite a few recordings of fixed RPM loops are necessary to achieve high quality results.

PROCEDURAL METHOD: ENGINE SOUND SYNTHESIS

Contrary to tedious loop editing work, a more procedural approach is to synthesise engine sounds based on additive synthesis or granular synthesis. 

Additive synthesis models the engine sound signal by sinusoids (harmonics) and residuals (noise). It is the Holy Grail of procedural engine sound synthesis, but it remains a challenging task to re-produce the complex modulation behaviors which characterise realistic engine sound quality.

Downsides:

• Hard to model complex modulation behavior
• Computationally demanding in real-time synthesis

Granular synthesis is a more practical approach because it makes use of snippets of a sound recording and thus inherits/preserves the short-time signal’s timbre. Given an engine recording revving up/down, one can analyse the underlying grains representing each engine firing cycle and then concatenate these grains in real-time.

Advantages:

• Inherits the timbre of realistic engine sounds
• Gain positions automatically detected
• Computationally efficient in real-time synthesis: a strong advantage of granular synthesis is that the complex analysis is done offline and the synthesis is very efficient in real-time. This frees sound designers from tedious loop editing work because the engine cycle positions (best crossfade points) are automatically detected by the analysis algorithm.

A good analysis provides precise grain positions synchronous to pitch (RPM)

AUDIOMOTORS AUTHORING TOOLS

AudioMotors’ granular engine reproduces engine cycle in a pitch-synchronous manner. The analysis stage is manipulated offline using the provided authoring tool such that game audio engine is only responsible for real-time synthesis.

AudioMotors Authoring Tool

Engine information settings

AudioMotors provides engine spec settings for the best analysis and synthesis results. If you know the engine type in advance, you can refer to automobile manufacturers for the cylinder count and the number of revolutions per firing event. There are also handy parameters such as harmonic factor, grain factor and randomisation for efficiently fine-tuning the quality.

RPM control

Drive control simulates engine load on/off

The control of synthesis is intuitive; namely, the engine RPM, that – just like driving a car – can be directly influenced by the physics working upon the vehicle. By using multiple instances for different miking positions, the switching of perspectives can be efficiently carried out.

AudioMotors also allows simulating engine load effects during acceleration/deceleration and gear changing for upshifting/downshifting.

A unique mode has also been developed for tyre-rolling sounds, which allows scratching the recording like a DJ for synthesising texture sounds with coherent timbre and seamless transitions. 

AudioMotors Authoring Tools for game audio includes a special DAW plugin version and a command line tool. It is meant for preparing the Car Data, which can be loaded and used in runtime. 

Export Car Data using Audiomotors Authoring Tools

The DAW plugin version has an Export button which exports the data necessary for runtime synthesis. The command line tool has not only the functionalities of the DAW plugin version but also advanced functionalities such as importing/exporting analysis results (Sound Description Interchangeable Format (SDIF)-compatible) for further manual correction. It is also a powerful tool for batch processing.

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