No doorbell, so I'll reference knocking. I tend to answer. It may seem counter-intuitive, but I live in a really lousy neighborhood - people generally only come knocking if they have a legitimate reason (political candidates, people who are at the wrong house, UPS, etc.). Anyone trying to "do dirt" isn't going to announce their presence. Also, Brooks (King of the Neighborhood, aka my dog) takes barking at the door very seriously. I've yet to look through the peephole at a stranger on the porch who doesn't take an involuntary step back when they hear him on the other side of the door.