Depends on the person. Usually it's all three.
People who are passionate about what they're saying would usually get all "excited" over it and thus their voice is raised in response.
People who are angry also get "excited" over what they are saying and lose the ability to think calmly and rationally for a while, thus their voices go up.
People who are trying to convince others can raise their voice, especially if they're starting to get ticked off that the people they're trying to persuade isn't buying it. But not all people who are trying to convince others do this.
If you put it all together, someone who is passionate, angry, and trying to convince someone, then you will definitely hear them raise their voices. I don't know the science or anything behind it, but from observations this is what I know.
