I don't talk much in crowds or in noisy situations, because both make me rather uncomfortable and I'm signifigantly more occupied with mentally planning my escape... however, I'll chat anyone's ear off otherwise
Human beings make life so interesting. Do you know that in a universe so full of wonders, they have managed to invent boredom? -Terry Pratchett
Another relatively quiet extrovert. When I'm with my extroverted friends, more often they carry the conversation, where I inject my two bits when it feels right or necessary to keep the convo going or to stir the pot a bit by teasing. My normal voice is closer to soft spoken than loud but it is fairly firm. I'm also comfortable sitting in silence with partners and friends.
Of course they exist. I am one of them. I attribute this to being "other-oriented" and want of emotional terms with a person or a topic. However, that tendency and urge to investigate someone's psyche and share some anecdote is nothing short of insistent.