There's a wind buffet sound that plays when you exceed a certain high threshold of speed.
In the film viewer I just watched a recent C205 sortie and as soon as I hit 250mph the wind buffet blared full volume, no ramping up. Normally you can't even hear this in-game until you start compressing and locking up. At different points of the film as I passed 250 it came on and as I dropped below 250 it stopped.
It doesn't start right away, even if film starts with you above 250mph. It has a delay then it kicks in. I verified this with another film I recorded just today, c205 also. Checked an me410 film and it does the same thing.
Thought I'd report it.