I have the same model, and I haven't noticed noise to the degree that you describe. There is a slight high-pitched sound that gets a little higher with speed, but not loud, and no more than reasonable expectation. I've had mine for two years, and spent all winter using it for heavy things like bread doughs (not insubstantial - three loaves of limpa at once would likely not have been tolerated by a smaller machine), and haven't had a problem.
Odd that it doesn't happen until you attach the bowl. I can't figure out an explanation for that one.
One thing about KitchenAid - about 6 years ago, the glass on my aunt's new KitchenAid oven exploded all over her kitchen while preheating (luckily no one was hurt). When she called KitchenAid, the rep said, "That's funny, usually when that happens..." Um, usually?