Hi there! Long time no see, etc... :-) On Saturday 02 August 2008, Benno Senoner wrote: [...] I think it'll need at least two parameters: rpm and throttle position. Even at a fixed rpm, an engine produces different (and usually much more) sound when you "step on it". Extremely tuned engines (long intake/exhaust overlap for maximum breathing at high rpms) also tend to sound pretty aggressive when engine braking in a certain rpm range. There is another problem, though: Electric cars tend to have very few gears (commonly only one!), as they don't really need any, thanks to the extremely wide power band of electric motors. This makes it pretty hard to come up with a realistict combustion engine sounds, as it's not just the sound that's missing; it's the entire driving style! I suppose you could just fake it by simulating shifts based on the speed and torque, but obviously, the sound cannot match the driving exactly. Well... Unless you simulate the whole thing; gears, clutch, narrow powerband and all - which, of course, would be entirely possible to do. :-) (And here I've spent countless hours mating a real Ford Duratec V6 engine with a Honda S2000 6-speed gearbox with an aluminum flywheel and a ceramitallic clutch in between... Oh, well. ;-) As to the actual sound synthesis, I think the best bet would be a combination of methods. For a realistic sound, you *will* need multisampling (unless you go for physical modelling), because most of what makes up the characteristic sound of a properly built engine (including intake and exhaust) is resonances that stay at fixed frequencies, or change only slightly with the exhaust gas temperature. (Temperature changes the speed of sound, which becomes a pretty significant factor with the temperatures we're talking about here. That's part of the reason why it's so hard to calculate optimal headers, BTW...) I've been thinking one might simulate an engine by modelling the headers and exhaust pipes as a number of resonant filters, and exciting that modell with noise bursts similar to what you hear from some old aircraft engines, which tend to have very, very short "stacks". You'd run the noise bursts as granular synthesis based on rpm, while tuning the exhaust resonances based on simulated exhaust gas temperature; that is, basically, higher frequencies when more power is produced. Oh, don't forget that you'll need to decide how many cylinders you want, and give each one a unique sound (slight differences in amplitude and exhaust resonances; smaller differences for finely tuned engines), or it'll sound like a one cylinder engine reving insanely high! :-) Also, typical american V8 engines (with 180° cranks, as opposed to the flat crank you'd find in a Ferrari V8) are pretty special, as they don't fire in a steady "every other bank" pattern, like most other V engines do. They sort of run as if each bank had two small cylinders and one large cylinder. You *can* make them run "properly", with a smooth, clean sound, but that requires a classic "180° exhaust system" (looooong tubes all around the engine; no good for high revs), or you need to turn the heads around so you can build a miniature 180° system between the heads. The latter can be seen on some old F1 cars, but I don't actually know where 180° systems are used. Low rev offroad applications...? //David Olofson - Programmer, Composer, Open Source Advocate .------- http://olofson.net - Games, SDL examples -------. | http://zeespace.net - 2.5D rendering engine | | http://audiality.org - Music/audio engine | | http://eel.olofson.net - Real time scripting | '-- http://www.reologica.se - Rheology instrumentation --'

Le 2 août 08 à 02:00, Benno Senoner a écrit : At least someone else in this community seems to start understanding the implications of the twin challenges of Peak Oil and Climate Change... Good start! But not sure simulating "combustion engine'" sound will be the most important thing we'll have to deal with in the next 5 or 10 years... Stephane