For example in forza, the game plays engine sounds based on how much we press the button. Are there different sequences of clips ? If yes how do they blend so well ? Or are they synthesized dynamically ?
There are so many parts to it as well - when the gear shifts, when you suddenly slow down at high speed, when you suddenly accelerate from stop. They all seem very realistic.
Edit: Thanks for the great answers everyone 🙏
I made changing farting sounds in my game Diarrhea 4 by manipulating the pitch. I bet that’s how they do it in racing games as well.
It’s certainly simpler than Forza et al, but there’s an open-source racing simulator, called Speed Dreams: https://www.speed-dreams.net/
If you watch the “Latest Release” video, there’s some engine sounds in that.
They seem to have a bunch of samples for how different car models’ engines sound: https://sourceforge.net/p/speed-dreams/code/HEAD/tree/tags/2.3.0/data/data/sound/
And then they modulate that in code, based on the car’s speed, gear, turbo etc.:
https://sourceforge.net/p/speed-dreams/code/HEAD/tree/tags/2.3.0/src/modules/sound/snddefault/CarSoundData.cpp#l171
They also do that for gear changes, tyre sounds, collisions and backfires.
From what I know about audio, I would expect AAA games to still use the same approach of recordings+modulations.
While it is possible to fully synthesize an engine sound, it doesn’t help you much with making it sound right in all different situations.
I remember exploring the Road Rash files as a kid and each bike sound was a single short click that just repeated rapidly. Times have changed.
Different studios take different approaches, I know when Polyphony digital was making Gran Turismo 7 they dramatically changed how they were doing audio by actually bringing the real cars into a dedicated recording studio. This isn’t the video I saw a few years ago, but it’s similar.
To my knowledge they may have been (still?) the only studio doing it this way.
There is also a one man wonder effort to improve the sound work of simulated engines by “simply” simulating the flow of air https://www.youtube.com/watch?v=J11c8mMN1PA
