I never rang the doorbell. I always knocked. It was a real knock. It could be heard....if they were in the hallway or the adjacent room. If they had the radio or TV on... oh well, they were busy and didn't hear me...maybe next time.
I used to laugh at people who peeked through the blinds but didn't answer the door. The worst was when I was walking back to the car from a not-at-home and a car drove by slowly. I thought at first he was a neighbor looking to see who we were, but later when we drove back down the street that same car was parked in the carport.
Now here's what's so funny. Apparently many of us were afraid of them, but they were afraid of us too. Even now, being out and hating anything to do with field service, I don't understand why people don't answer their door. It's your damn house for God's sake, have some guts, answer the door and tell whoever knocked, whether it's JWs or Mormons or a vacuum cleaner saleman, that you're not interested and ask them to leave.