The Caterwauling Charm sets off a loud wailing noise when an unauthorized person enters the target area.
References from the canon
- Hogsmeade was under a Caterwauling Charm that would go off if anyone moved around outside while curfew was in effect (DH28).
"caterwaul" Eng. to make a screaming noise like that of a cat during mating season
From the Web
"Caterwauling Charm" from Harry Potter Wiki