Do GM's announce check?

Out of curiosity, do GM's announce check when they play?  Or is it understood that the opponent is good enough to know that he/she's in check?

Well I think even people of our rating will understand that if a piece is attacking the king , then it is check, so i dont understand why GM's will do it

no they dont. if you ever play OTB its actually considered rude by some people to announce check.

I doubt they announce check; even at my level no-one bothers. Occasionally if I am playing someone lower rated they will announce it, but I don't mind too much. It annoys me slightly when I return to the board and they feel the need to point out which piece they moved, though; it almost feels like an insult that I can't even notice what has changed on the board.

Honestly I never announced check in an OTB tournament, and I'm not surely a GM.

I think there is no need to annouce check in a OTB tournament, because if the opponent is not able to understand alone that is under check, maybe he/she is not ready for a real tournament...

^also not announcing check can win you the game.

I saw a game between a guy i know (2200ish) an some other 2200 where it was something like this. (obviously not exactly, since this was over a year ago)