Engine sound in FS 2002 default planes.

[Guest]

Why does the engine sound go up in frequency when rpm goes down after adjusting the propellers? It should go down as the gauges does. Is there a fix?Keep'em flyin'!Bertil PerssonESPC Fr

[tgibson 11]

FS bug - haven't heard of a fix...-- Tom GibsonCalifornia Classic Propliners: http://www.calclassic.com/Cal Classic Alco Page: http://www.calclassic.com/alco/Freeflight Design Shop: http://www.freeflightdesign.com/ San Diego Model RR Museum: http://www.sdmodelrailroadm.com/Drop by! ___x_x_(")_x_x___

[pacosancas 0]

Hi,Rather than a bug, it's a very poor modelling of the sound in FS. The problem is that, on a normal plane, the propeller sound frequency, as you correctly point out, varies proportionally to the prop rpm, but its volume (and, furthermore, its timber), varies according a complex law, mainly based on the propeller's advance ratio and the torque delivered, and is not linear at all. MS lets you create a sound set for each aircraft, created as the sum of many individual sound files. For each individual file, you are allowed to vary frequency and volume according to serveral variables to choose among, but the problem is that both the volume and the frequency have to be controlled by the same variable: as a result, it is not possible to control the frequency of the propeller sound by the rpm and the volume by the torque. Either you control both by the rpm, or you control both by the torque (as MS did). It is possible to make the propeller sound be controlled in frequency by the rpm, but the result is that the sound will not change at all when the power levers are moved. Even with this being quite realistic, specially on some aircrafts, people do not like it, and MS decided to go the easy way: make people happy with unrealistic sounds. In a turboprop, it is more easy to make a sound set a bit more realistic, as there is the possibility to control the propeller sound by the propeller rpm, and add a jet sound controlled by the gas producer rpm. These two when played together make a half decent sound, far better than MS default aircrafts. This is what I tried to do in my ATR's (so far I have seen only one more sound package which addresses this problem by another author, which I do not remember now). In a piston engine, this is not possible, as there are no two parts of the engine rotating at different speed (else than the turbocharger if fitted, but that is not a dominant sound).The fact is that after releasing each of the ATR's, I got a ton of mails pointing out that I was wrong with the sound set, as the prop frequency wasn't changing with the power lever as they expected! It seems that most people like the MS cheat. I have been listening to and recording turboprops when taking off, and there is a very peculiar effect on the volume of the sound generated by the props. Whith the the engines at ground idle, the volume is quite high. When the aircraft takes the runway, it can be very clearly heard when the idle gate is placed in fligh idle position, as the frequency will increase by several tones, and the jet sound will do so, while the volume increases only slightly. When takeoff power is applied, the volume of the propeller sound will go down to almost silent, while the acceleration of the aircraft tells you that a lot of power is being applied. Then, as soon as the aircraft starts to gain speed, the propeller sound will start to recover volume to reach its normal level after takeoff. All this without a change at all in the frequency, which tells you that the props have been at 100% rpm during all this process. Well, this cannot be modelled at all in FS with the tools available, and in fact MS default sounds do almost opposite. In spite of this, very few people believe these explanations and most insist that MS sound modelling is best. So, why would MS bother to correct their sounds?PacoStultorum numerus infinitus est.

[Guest]

Thanks Paco! Interesting! Is it possible to make the adjust as an user? Or do you know a fix for it?It's a friend of mine who is the user. I mainly use Fly! 2K - Mac. Sometimes I run FS98 on PC emulator. The problem does not occur on those sims. And some of the thirdpart piston powered planes for 2002, for instanse the Beaver. does not have this problem.If Tom Gibson is reading my message I can tell you that the DC-7C also is running without this problem. Could it bee because they're upgraded from FS98?Keep'em flyin'!Bertil PerssonESPC Fr

[pacosancas 0]

Hi,The (partial) fix is in the sound.cfg file associated to each plane. Not rocket science, but you'll need to study the structure of this file. In one of the SDK's released by MS there is some general description of what each entry in the file does.Stultorum numerus infinitus est.

[Guest Ron Freimuth]

>Hi, >>Rather than a bug, it's a very poor modelling of the sound >in FS. The problem is that, on a normal plane, the propeller >sound frequency, as you correctly point out, varies >proportionally to the prop rpm, but its volume (and, >furthermore, its timber), varies according a complex law, >mainly based on the propeller's advance ratio and the torque >delivered, and is not linear at all. MS lets you create a >sound set for each aircraft, created as the sum of many >individual sound files. For each individual file, you are >allowed to vary frequency and volume according to serveral >variables to choose among, but the problem is that both the >volume and the frequency have to be controlled by the same >variable: as a result, it is not possible to control the >frequency of the propeller sound by the rpm and the volume >by the torque. Either you control both by the rpm, or you >control both by the torque (as MS did). >>It is possible to make the propeller sound be controlled in >frequency by the rpm, but the result is that the sound will >not change at all when the power levers are moved. Even with >this being quite realistic, specially on some aircrafts, >people do not like it, and MS decided to go the easy way: >make people happy with unrealistic sounds. >>In a turboprop, it is more easy to make a sound set a bit >more realistic, as there is the possibility to control the >propeller sound by the propeller rpm, and add a jet sound >controlled by the gas producer rpm....>Paco Don't know if it helps, but there must be two different RPM tokens for Reciprocating prop engines. One displays the engine RPM, the other the Prop RPM. Normally they are the same, but with a geared engine they are in the ratio of the gear ratio setting (in aircraft.cfg). Even if the gear ratio is 1:1 there are two RPM variables available. I know this because I used the FS2K2 Baron panel with an AC that has a pair of geared engines. The Baron RPM gauges show prop, not engine RPM. However, a test gauge shows crankshaft RPM. Another test gauge I have shows both crankshaft and prop RPM. I'm quite sure the Cessna tach shows engine RPM, since it went off scale with a 5800 RPM engine I set up. While the Prop RPM must have been nominal (<2700 RPM). Turboprop gauges show prop RPM, "RPM" is for the gas generator. While Prop_RPM * Gear_Ratio = N2. There are also two Torque values, I'm not sure if both are tokens or what I see is calculated by a test gauge or app. However, the prop and crankshaft RPM's are always related by the Gear Ratio. The Prop RPM control changes both. Regardless, a geared engine should should faster than one that isn't. Especially if a 5800 RPM Rotex.Ron

[tgibson 11]

Hi,Yes, FS98 models don't seem to have this problem. It was only when we were converting the propliner FDE's to FS2002 that this bug became apparent (unfortunately).Hope this helps,-- Tom GibsonCalifornia Classic Propliners: http://www.calclassic.com/Cal Classic Alco Page: http://www.calclassic.com/alco/Freeflight Design Shop: http://www.freeflightdesign.com/ San Diego Model RR Museum: http://www.sdmodelrailroadm.com/Drop by! ___x_x_(")_x_x___

[Guest]

Thanks! I'll see what we're able to with this info.Keep'em flyin'!Bertil PerssonESPC Fr