What noise does ball joints make when they are bad?

They make no real noise. Have themn inspected by a professional if you suspect they are worn. There is no real noise they make, but any noise from the front end could result in bad things. So, if you hear any noise, I recommend that you go get it checked out. One thing I do know that they will tell you though, when your car is up in the air, try grabbing ahold of the bottom and top of the outside of the tire and try moving the tire back and forth gently. If there is ANY play, chances are, something needs to be replaced. sometimes they will make a popping sound while turning.