Imitated voice
In short: A character copies a familiar voice or call to mislead a listener.
Motif
How does it work in the tale?
The stranger at Tselane’s door uses her mother’s call. The wolf speaks in the grandmother’s disguise in Little Red Riding Hood. In both scenes, the reader knows who is speaking before the heroine does.
Whose voice is at the door?
In the 1889 record of Tselane, the girl opens the door after mistaking the call for her mother’s. In Grimm, the wolf first speaks to the grandmother as if he were the girl, then greets the girl as her grandmother. In both scenes a voice serves as proof of identity. The disguise works because the listener expects someone familiar.