Time to talk about audio in Assetto Corsa Competizione!
Before the development of ACC started, we scratched our heads about which audio middleware would fit our needs with UE4. After some experiments and internal testing, we confirmed FMod because it has been improved over time and we can count on a quite fast support.
Me and my mate Alvio Costantini (the KS coder that is taking care of the FMod implementation in our code, among other stuff like replay and highlights system) rewrote the FMod project structure from scratch and believe me, it was (and it is) a big challenge. Just an example: in Assetto Corsa, the engine sound event used to run just two parameters (rpm and throttle). The lack of time prevented us to make further big changes to the existing audio structure. In Assetto Corsa Competizione there are HUGE changes to that. For example, the same engine sound event relates to over 10 unique parameters. This puts the immersion bar at a new level but making so many things work together as expected requires almost double the working time than AC1.
That said, I want to point out some of the main aspects involved in the audio development for ACC:
CARS - ONBOARD
I could write for hours here... where to start? Well, the car is much more alive than before, with new features, better sound spatialization and overall brightness. Down-mixing from surround systems to stereo configurations works now as expected, keeping levels coherent in the mix. Just this is already a big leap ahead compared to AC1.
The new audio design allowed me to implement many details that were missing in AC1. The transmission behaviour is directly driven by physics. Some wobbling that in real life is produced by the dog-leg transmission is still WIP here, but as said we'll try to improve that together to the physics guys.
Gear shifting is now more rewarding for your ears... personally I totally love downshifting with the Huracan.
Also backfires are not simply a random thing, but there are different "types" of them that are related to the engine specs (N/A or turbo), rpm, throttle position and fuel flow.
The traction control, another great improvement physics-wise in ACC, is also clearly noticeable sound-wise when it kicks in, bringing an important information regarding your driving style and efficiency.
There are some very new sounds like the gearbox compressor and the ABS. The first one (a sort of buzz you will hear after some downshift) happens because of the hydraulic actuators of the gearbox work at a certain pressure. When this goes down under a certain value, it gets recharged by an electric pump that makes this distinctive sound. In ACC, its behaviour is exactly like in real-life: it calculates the amount of lost pressure and recharges it when needed.
Talking about ABS, well, imagine to engage it in your stock car. Done? Scratch it. Think about a race-car as a big resonance chamber (no soundproofing, stiff setup, pillow ball bushings and so on). The amount of noise and vibration that the ABS can make is really REALLY high. Again, this is very informative about your driving style and any change you need to bring to your driving style and/or setup.
As for the ABS and TC systems, now you can understand if your brakes are in the optimal range just by hearing them. After a certain temperature, you will hear a kind of squeal, that will turn in a more subtle whistle when they get hot but watch out and don't go too high with the temps, otherwise you will face (and hear) the fading effect.
Scratches produced by the car bottoming out is another important aspect you have to keep in mind working on the setup or driving style. Climbing over a curb or bump sometimes is simply not technically feasible because of the car height and suspension travel, but if your car is scratching your bottom all over the place, probably you're driving too low.
Another new feature is the engine startup/shutdown procedure! From a "cold and dark" situation (i.e. everything off), remember to enable the ignition first (Shift - I by default at the moment of this post) and when you hear the fuel pump, you can engage the starter by pressing S. If you engage it without ignition on, you will only hear the starter motor running. This will provide great action during pitstops, where shutting down the engine is mandatory.
Last but not least: driving along a wall/barrier (if you are not in a reverb zone like the main straight), casts now reflections of your exterior engine sound.
CARS - EXTERIOR SOUNDS AND TRACK CAMERAS
Exterior sounds have also been improved. Now there are dynamic reverbs and other filters that are related to the distance and position of the car(s). The aim is to achieve a coherent behaviour when many cars are involved without hitting the headroom barrier but providing at the same time a clear sound experience watching a race as a spectator or just enjoying a replay from the track cameras.
Watching a replay of your car alone on the track is now more enjoyable because there are many more sounds involved besides the car itself: crowd from the standings, track speakers, weather, soundscape, rumble passing over the curbs (if the camera is close enough) and so on.
TIRES
This is another big change. As for the engine, the tires event sound includes many parameters like slip ratio, tyre load, wet level, marbles, puddles, surfaces, brake temp, ABS status and some other things that I can't even remember now! If you are an AC1 user, you will immediately spot the differences in sound and behaviour.
Remember: marbles are the evil (and believe me, they make a REALLY loud noise in a real race car) if you are driving on dry conditions, but could somehow help you on wet because they work like a sort of basic "tread" for your tires. Please read Aris' posts here on the forum for more information about that.
A note about the level of dirtiness of the tires: in future releases, if a car ahead you collects dirt on its tires, you might hear some chirps hitting your windshield or body. This is not a fake effect, but it's indeed based on the amount of dirtiness gathered by the car ahead.
WEATHER
Talking about new features, the changeable weather is for sure one of the most requested news in ACC. It was not easy, audio-wise, to work on the different weather conditions without risking to "distract" the driver with too many effects. Our aim (and hope you enjoy it) is to provide to the user the same kind of "awe" that a real driver experience in unusual conditions. Personally, driving and hearing the drops on the car body and the tyre noise intensify, lapping faster and faster under a heavy rain or during a race on a wet track, makes me goosebumps. We hope that the whole "package" (graphics, audio, physics and FFB) can bring to you the same experience.
Funny hint: the wiper sound is related to the rain level, try to turn it on when the windshield is dry.
TRACK LIFE
As said before, the crowd is audible and their loudness is related to their number. Sound speakers along the track also work, as well as pit alarm sirens when you cross the pit lane entry line. Barriers and walls make basic reflections of your exterior engine when you drive in cockpit/onboard cameras. In future, you will hear authentic pit stop sounds, different for interior and exterior cameras.
WHAT'S NEXT
I can't talk about all the aspects that are involved in the audio making, also because some of them are still on paper or just WIP, but we are doing (and will do) our best to provide the best experience possible. Hope you are enjoying and will enjoy our work. Furthermore, don't be afraid about reporting issues or constructive (aka doable/realistic) critiques.
Thanks in advance for your feedback! Now, let's go back to work on the next car on the list.
EDIT: BIG THANKS to the real Blancpain drivers and SRO for their precious help, support and availability. Much appreciated!
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