Like I said all cameras make a sound, there is a mirror that is slammed up in a spilt second, you can hear that, no difference on the 7D. Most digital cameras are a lot quieter than film camera of yesteryear. Unless you lock up the mirror there will be noise, normally only top of the line cameras can do that.
The T2i and the 7D have the same sensor, so you get a heavier and more durable body with the 7D but the images will be the same.
One area that the build will come into play, the 7D would handle weather better. Pro cameras have seals that give some protection from the elements that consumer cameras do not.