Just as the British are stereotyped as tea-drinking complainers with bad teeth, Americans are themselves often the focus of gross generalis(z)ations, specifically at the hands of their cousins across the Pond. One of these generalis(z)ations (among many) is the notion that Americans are loud and obnoxious—that they are incapable of opening their mouths without bringing themselves, inadvertently, into focus.
But just how much truth is there to this notion? Well, as with most stereotypes, it's all in the context. Indeed, one context often cited by my British compatriots is that of the American abroad—the one who asks for directions to Bucking-HAM Palace, or chats raucously to his buddy on the Underground. American tourists, insist some British locals, are the loudest of them all.
However, my theory is that such vacationers are not particularly loud at all; they simply stand out in a place like England for the very reason I do in Indianapolis: their accent. There's a certain level of glamo(u)r that comes with hearing an American accent—the perceived brogue of Hollywood—hovering its way across the humble surroundings of a quaint British town. As members of a smaller nation characterized by an underdog spirit, many Brits are not so inclined to admit this—clutching instead to the idea that "Yanks are so in your face."
But I think we British often mistake directness for loudness. An American in a British chip shop, for example, would be more likely to construct his or her order as "I'll get fish 'n' chips" than use the more face-saving British approach, "can I get fish 'n' chips, please?" In other words, Americans don't seek permission to purchase their food like the British.
However, on the subject of food, there is one contextual setting in which Americans—at least in my experience—tend to be quite a lot louder: restaurants. In the U.K., of course, it is customary to keep your restaurant chatter to a medium level and at a relaxed speed. In the U.S., the engines of dinner conversation are revved up to the max and the words come out at a hundred miles an hour. You can see a microcosm of this every time two Americans are out on a date. I've actually lost count of the number of times I've overheard a guy try to impress a girl by raising the volume of his voice while talking at her rapidly for two solid hours about his company's sales figures. She's not interviewing you. Calm down.
Those last two words—"calm down"—might also be directed at someone whose sports team has just lost a pivotal match. Perhaps this is not the best thing to say to NFL or basketball fans, many of whom support their team with all the vocal tenderness of a drill sergeant. That said, such supporters would do well to beat the volume level of the average (and sometimes above-average) British football supporter. In fact, if you yourself are British and are in the business of putting the words "loud" and "American" in the same sentence, stand on a football and NFL terrace in Britain and America respectively and get back to me with the results. I guarantee you that the British are louder. And drunker.
One other place where the Americans win, though, is the news studio. I'm not sure if it's the production quality or just the general delivery, but American news anchors and guests often sound like those two Americans on a date. Except this time it's not one person talking at the other, but two (or more) people talking at each other. All the while, the din of their voices swarms through your brain long after the TV has been switched off—like the unforgiving hum of a bustling casino. In Britain, of course, news readers project a slightly reserved—sometimes concerned—tone, with newsroom debates taking the form of question-and-answer discourse rather than all-out war (note: there have been notable exceptions to this).
Of course, there are many specific scenarios in which the British and the Americans are louder than the other. But if we were to listen in on the mundane everyday conversation of the average American, we'd probably find no greater level of volume than with the average Brit. By "everyday conversation" I mean one that takes place with a spouse about whether he or she enjoyed that bowl of muesli, or with a friend regarding his or her day at work. That sort of thing.
What I'm saying is that Americans are not just some group of noisy homo sapiens with no off button. They, like anyone else, are equipped with several buttons—each one representing different settings for different situations. They have social rules, just as we do, over when to raise one's voice and when to tone things down. For every loud restaurant chatter, there are hushed library whispers; for every supposed loud tourist there are quieter travelers like Rick Steves; and for every noisy news anchor there are... NPR news anchors.
What I'm saying is that context is everything.