I'm with Dawn. It absolutely sounds like Tourette Syndrome. I have a friend whose son developed this at age 13 and it involves all kinds of involuntary sounds, movements, tics, and so on. He went through a barking phase, and also through a swearing phase. There is nothing this person can do about it. People who complain can make the person even more stressed, which can cause an increase in the tics. That doesn't mean they are CAUSED by stress, but rather they can be aggravated by additional social pressure.
I know it's annoying, but imagine being the person suffering. It's a life sentence. My friend's son has been asked to leave restaurants and theaters, religious services, college classes and more. He was much happier when he found understanding and compassionate people in his surroundings.
The more we educate ourselves about these things, the better off we all are. I know my son learned a lot by being around my friend's son (in fact, that's how he learned to swear!! LOL!). But later we would see or hear people in public places, and my son would say, "Mom, do you think that person has Tourette Syndrome?" A lot more compassionate than saying "Boy is that person weird and inappropriate."