ding sound when you headshot a special infected?

[remi]

Im talking about this sound https://www.youtube.com/watch?v=qZC5gtOw3DU

I used to hear it whenever I headshot a special infected, but not anymore, anyone knows how to fix it?

[supersand]

There is no sound that plays when headshotting any infected, only a ding sound when you land a killing blow on a Special Infected and a red "Player killed X" message.