Alternatively, try standing outside the door with a claxon, giving your guests a two-minute warning.
From the guardian.co.uk
You can replace the claxon with any sound.
From the badlanguage.net
Back on the road, I noticed the frequent bright yellow claxon horns on the telephone poles, used to warn of tornados.
From the ocregister.com
An army deuce-and-a-half rolled by, claxon blaring, three dozen faces peering from the back and five more Vietnamese sitting on the hood.
From the time.com
More examples
Honk: make a loud noise; "The horns of the taxis blared"
Klaxon: a kind of loud horn formerly used on motor vehicles
Honk: use the horn of a car
A vehicle horn is a sound-making device used to warn others of the approach of the vehicle or of its presence. Automobiles, trucks, ships, and trains are all required by law to have horns. ...