Yes yes, I've live in Europe for 13 years. When there is an American group in a restaurant, you KnOW, no matter where in the restaurant they are.

I've observed this in Hungary, Germany, Spain and others.

My theory is that most Europeans, living all their life on a crowded continent, tend to move in closer to talk, and hence talk at a lower volume. Americans, used to grand amounts of space, sit back and project their voice.

I'm from istanbul and having seen tourists from every place on the world, I think the loudest are the Germans and the Saudis. When they speak on the tram I usually just give up with the earphones :)