how to visiting someone in their house

If I want to visit someone in their house, when the door's closed and I don't find any doorbell, can I yell "Sumimasen!" outside the house? Is it a rude or unrude manner? since the loud noise may disturb the neighbour.
And sometimes in anime, I saw guest enter the house, which is not locked, and yell "Sumimasen!" while standing up and waiting in the genkan. It's seems a housebreak, or it's just me who got wrong impression about the scene?
What the right thing to do? Thank you.

You might knock lightly on the door, or if you want to try calling out, for visiting someone in their home, you would want to say "gomenkudasai."

I don't really think that people would leave the door unlocked nowadays....

both your question and anime way are correct

If so, I open the door and yell "Sumimasen...dare ka imasen ka!".
But I never stand on the genkan, unless there is my very close friend's house.