Yes, the enemy hears your character yelling. Here is just one example of when it got me killed:
http://www.youtube.com/watch?v=xN2DAs6zNcY
I cannot see how this is good for gameplay when your character announces his presence to the enemy players. It removes the whole point of sneaking/flanking opponents when at any given moment your character could bellow and give away his position.
Worse, it happens at moments when you may not even be aware that a team mate was killed.