This bug is still not fixed, I have the same problem on an Asus Xonar STX 7.1, Doesn't matter what sample rate I put in-game.
Cannot replicate in singleplayer, happens 90% of helicopter crashes on multi-player. It sometimes happens when the helicopter takes light damage also.
It doesn't matter what you crash into, happens when you are hit with AA, crash into another vehicle or helicopter, crash in water, hard landing with god mode.
The sound is a high pitched screeching about 4-7 times louder than all the other sounds. It's horrible and can cause ear damage.
I also have the same bug where FPS drops to about 15% of normal when auto-cannon on Tigris\Cheetah impacts, same with jet cannons, I can fix this by lowering sample rate but it's a bug nonetheless.
I hope the new audio team can fix these bugs, the bugs are fucking horrible!