The times I sound angriest to other people is when I'm highly fruststrated. People insist on perceiving me as angry, and sometimes they act afraid of me. But I insist on the fact (it is a fact, as far as I'm concerned) that what I'm feeling is frustration, not anger.
A typical situation where this comes up is if I have to do something complicated (e.g., get help with a computer problem) over the phone at work. (It does happen when I'm dealing with someone in person, too, but I tend to avoid that.) Apparently I come on sounding very angry, possibly nasty. But I'm not angry. If I were angry I would be angry at someone (the person I was talking to, presumably). I am not angry, I am frustrated by an intrasigent situation.
That's when I may raise my voice (not in anger but in frustration) and even use "bad language." The way you can tell I'm really angry is that I'm likely to be crying, a reaction I do not have to frustraton.