Why people raise their hand when they knock a door?

Question

Because you can knock a door with your hand down as well and it would be more convenient?

In: Physics

Answer 1

So that the knocking sound is closer to the person’s ear.

If you knock too low to the ground, the “knocking” sound waves might go right under them if they’re standing up. Especially if you’re knocking on a very tall person’s door.