The Paraguayan "doorbell"

No-one here has doorbells, and doors are often open or token. If you're standing outside someone's house and want to get their attention, rather than knocking, you clap your hands. If they're in, they emerge to receive the applause!

The fact that clapping is audible and effective as a doorbell is indicative both of the tranquility of the town and of the lack of insulation / doors that close properly.

Maize and Mimi