Have you tried disabling/enabling Fast Bounce during export?
 

Yep, that was about number 4 in the sequence of elimination steps. No difference.

Have you tried exporting without dithering? (And obviously no bit reduction)

sounds a little like a bad ground.
 
are you using anything when mixing down that you don't use during other operations ?
a light maybe ? a outboard effects rack ?
 
sounds almost florescent.
 
I find in these cases, sometimes, not always.. its the obvious, its something right in front of us that we wouldn't have even thought about.
check your surroundings.

I don't see where the grounding would be an issue, there's no ground noise in the live tracks and only when I'm exporting is where the noise is added, and that's being done at high speed. And again, if the tracks are frozen prior to export there's no noise at all ground or otherwise. I'm going to bite the bullet and try a Sonar patch update and see if that works.

What version of X3 are you on? Are you using the Console Emulator?
 
I seem to recall the first couple patches (a, b...) were getting complaints about some kind of noise when the Console Emus (or maybe it was the new Tape Sim) were being used. It was fixed by one of the patches (X3c I think). I also remember something about disabling the 64 bit double precision engine in preferences helping some people get rid of it in the meantime (but not all). I did not experience any of that though and it was many months ago.
 
So yeah... definitely try patching.

Very good point Beeps...  The issue was using the Console Emulator with the 64bit double precision option enabled.  However, it's possible to keep the 64bit option disabled during playback but still have it checked on just for export (that's what I do).
 

stevec
Very good point Beeps...  The issue was using the Console Emulator with the 64bit double precision option enabled.  However, it's possible to keep the 64bit option disabled during playback but still have it checked on just for export (that's what I do).
 

Are you still experiencing a problem with this, Steve? I thought that was long gone by now.
 
I never experienced it though (and did test it with "b", "c" and I think even "a" for the brief period I had it installed). The only PC noise weirdness I'm getting is from pressing the power button on the Concrete Limiter but I'm starting to think that has something to do with an instance of the Tape Emulator downstream... but I may try disabling 64bit just to see what that does.
 
 

No, I'm not - I was just pointing that out for the OP's sake since it seemed to be a very logical reason for his issues (pre-X3e).