I knock on people's doors for a living. Been doing it for nigh on eighteen years now. I received no training for this important skill, just learned my own techniques as I went along. After Mrs Kelly complained at me that her husband was in and did not hear me I upped my game. I have regularly been accused of knocking like the police. Once I was accused of knocking like the debt collectors, but I think that said more about the customer than about my knocking. A couple of times I have been complained at for startling people, and then the other week a complaint for knocking too loud and disturbing a baby (my ESP was turned off at the time and I didn't notice there was a baby in the house). Yesterday I was complained at for (just potentially mind you) denting someone's new front door with my bionic knuckles. Most people just say thank you when you arrive on their doorstep on a cold and rainy November afternoon but whatever.
Stay safe. See you tomorrow.