In the case of Hereditary, the young Charlie, played by Milly Shapiro, used a specific tongue click to create a jarring sound effect to startle viewers.

A tongue-clicking sound could mean, "That's not what I wanted to happen." The dictionary spells this "tsk," though I'm not sure I say the "k." If you click once, you're disappointed in something.

That’s when the tongue-clicking begins. Daniel, Brian, and Megan are making loud, sharp clicking sounds with their tongues so that they can hear what I can see.