How does Tom Buchanan speak? What is the tone of his typical manner of address?

Tom Buchanan speaks like a person who has never been opposed, like one who has always been listened to, and as though he believes himself to be better than everyone else.  Nick describes his voice as 

a gruff husky tenor [which] added to the impression of fractiousness he conveyed.  There was a touch of paternal contempt in it, even toward people he liked-- [...].  "Now don't think my opinion on these matters is final," he...

Tom Buchanan speaks like a person who has never been opposed, like one who has always been listened to, and as though he believes himself to be better than everyone else.  Nick describes his voice as 

a gruff husky tenor [which] added to the impression of fractiousness he conveyed.  There was a touch of paternal contempt in it, even toward people he liked-- [...].  "Now don't think my opinion on these matters is final," he seemed to say, "just because I'm stronger and more of a man than you are" (7).

In addition to the arrogance conveyed by Tom's demeanor and bearing, his voice communicates a similar sense of his own importance.  His gruffness is overwhelmingly masculine and powerful, and his way of being constantly touchy and sort of irritated make him seem as though he doesn't like anyone, even the people whom he actually does like.  Tom is authoritative, brooking no opposition, even though he would never say that such opposition was unacceptable.  It's just that his tone implies the question: do you really want to disagree with me, you puny runt, with all my bravado and righteousness?

During dinner on the first night Nick goes to visit, Tom blurts out, "violently," that 

"Civilization's going to pieces [....].  [I]f we don't look out the white race will be -- will be utterly submerged [....].  It's up to us, who are the dominant race, to watch out or these other races will have control of things" (12-13).

His racism further conveys a sense of his cruelty and superiority.  And his tone, here, emphasizes his "fractiousness" again; he is peevish about a threat where none exists.  He is the threat, not those people who he believes to be a danger to the "Nordic" race (13).