I don't drive a motorcycle, but I really want to and I would say that I know a good deal about them too.
Oh that's cool, I'm scared of them to be honest. Why are they so loud?
Well I think how loud they are depends on the type of motorcycle: street, off-road, or dual purpose.
Which one would be the quietest? That's the one I want. I do like how fuel efficient they are though!
As far as I know, street bikes need to be a certain level of quiet whereas the others don't.
That makes sense. I suppose people in neighborhoods wouldn't like all the noise. 
Oh definitely, noise levels are a big deal. There are also quite a few different designs, like some are better for long distance and some are better for commuting.
It's smart to use them for commuting because they use so little fuel!
Agreed, the fact that bikes are so much smaller than a car and use only two or three wheels really helps with fuel economy.