That is the sound of too many fps, believe it or not.

It happens when the fps goes above 120 or about. It somehow causes the sound to distort.

So my guess is that you're running unlimited without v-sync.

At least enable v-sync, and you might as well set your fps limit to your monitors refresh rate (probably 60 hz/fps).

This is how I get FS9 to run the smoothest (using TrackIR).

Just tried it, and it worked like a charm! What a bizzare phenomenon... I never would have thought of it. I guess FS9 just wasn't designed to be ran at ~120 FPS. THANKS so much for the solution! 

Yep, it's one of those luxury "problems" I guess.

Another "fix" would be to install more addons to bog the sim down so you stay below 120fps

Wow, I never knew that too many fps could cause a problem like this! Well, the old saw "Too much of anything ..." has been proven again. Kudos to Neumanix for knowing answer to the obscurest issues!

THAT is unreal!  Never would have thought of that (or suffered that) as I never even get CLOSE to the "buzz" on my system.

Peter to the rescue!

Well damn. FS9 isn't broken after all lol. She's still kicking.

I'm not too surprised the fps has caused an issue although I certainly didn't expect it at any stage during this thread...yet. I'm skeptical about even a 60fps being used for FS9. The reason is simple, FS was a very hardware intensive sim when released. As a developer, MS certainly were aware of this and the hardware to run FS9 at the frame rates we use today would never have been taken into consideration during development. Are there adverse effects of using too high fps given the way FS functions as a program? I've always believed there was a good chance there would be. I'll often suggest to problem shoot certain FS issues dump the fps down to 25 as while it runs at 60fps or more you just cannot be sure the high setting isn't causing a problem. Unfortunately, I find anyone running at high fps isn't too keen on going down to the 25-30fps range even temporarily!

I'm not too surprised the fps has caused an issue although I certainly didn't expect it at any stage during this thread...yet. I'm skeptical about even a 60fps being used for FS9. The reason is simple, FS was a very hardware intensive sim when released. As a developer, MS certainly were aware of this and the hardware to run FS9 at the frame rates we use today would never have been taken into consideration during development. Are there adverse effects of using too high fps given the way FS functions as a program? I've always believed there was a good chance there would be. I'll often suggest to problem shoot certain FS issues dump the fps down to 25 as while it runs at 60fps or more you just cannot be sure the high setting isn't causing a problem. Unfortunately, I find anyone running at high fps isn't too keen on going down to the 25-30fps range even temporarily!

Well, I bumped the sim 'down' to 99.8 FPS, and so far I haven't encountered any problems whatsoever. I sometimes get bad FPS fluctuations at places like JFK, but nothing unexpected. 

A bit of necroposting.

I'd just discovered the same thing with my new win 10 pc. I'd even gone as far as buying a soundcard in the hope that it would keep up with the framerate. No joy.

I've concluded that FS9 is coded to perform graphics and sound in separate something-or-others (timeline, thread, chain of events?) and that graphics takes priority over sound. Also, I suppose that each piece of sound must have a minimum duration to be intelligible.

Because each chunk of sound has to play for a minimum period in order to be heard properly, at a high fps it's impossible for the sound to keep up with the graphics so FS9 repeatedly dumps some sections of sound in order to move on to something appropriate to the next frame. Each dump causes a pop and when a series of pops happens fast enough it sounds like a buzzing or a rumble. Below a certain framerate there's enough spare time for the sound to play fully, hence my earlier erroneous belief that a low IRQ priority for the onboard sound was to blame and that a dedicated card would solve the problem. Seems not.

On the other hand, win 10 limits the fullscreen framerate to the monitor refresh rate, something that apparently can't be overridden. On the new PC, that has its own downside. I've concluded that FS9 is coded to perform a defined and limited number of graphics operations per frame. On the new machine there's plenty of time in each frame for photoscenery to load comfortably. But... each relatively lengthy frame has a lot of idle time at its end so by the time a sufficient number of cycles has been completed, I'm twenty miles beyond and the photoscenery never reaches full res. In windowed mode 300 fps still affords enough time (a three-hundredth of a second) for all the graphics operations to finish before the next frame and my photoscenery reaches high-res mips a lot quicker, usually before I've over-flown.

It's interesting that over the ocean with a clear sky, I can get Shift+Z to show @99 or even A50 fps, which implies that MS never expected 4-digit framerates (the reported number won't roll over into the next decimal place: it uses the next character as a substitute. Hence the colon is 10, the semi-colon is 11, smaller-than is 12, equals is 13 etc).

Equally interesting is that UK2000's EGLL with full AI still brings the FPS down to 29. On the other hand, Traffic Explorer says the number of aircraft is 455 so I'm happy...

It does, though, mean that I only have a choice of fast scenery with sound artefacts, or good sound but photoscenery that never fully loads...

On 2/3/2018 at 5:38 PM, Dave Morgan said:

On the other hand, win 10 limits the fullscreen framerate to the monitor refresh rate, something that apparently can't be overridden.

No, you still have control over this. I use nvidia Inspector for my game profiles, and if I set my FS9 profile to force vsync OFF and I set unlimited frames in FS9, then it pumps out

as many frames as it can. If you have a nvidia card I can recommend setting your vsync to "fast sync". It eliminates tearing and allows fps above your monitors refresh rate. This is as close to gsync you can get without a gsync monitor.

Ahh, sadly it doesn't work for me and my GeForce GTX 1060. Maximised window is fine but full screen is 60 fps max... I already had vertical sync forced off. Fast sync made no difference. Not that it matters, because over 100 fps or thereabouts the in-cockpit sound is rubbish anyway. I have been thinking about installing XP in place of MS gaoler 10 professional. I don't know if using the display port is limiting it. Maybe I should try HDMI instead.

 

Out of interest, and on the assumption that it may be some other setting,

Pref. refresh rate: highest available

Triple buffering: off

Vert sync: force off

V sync smooth afr behaviour: off (what is that?)

Tear control: standard

 

D