Muffliato Charm

"There had been a hex that caused toenails to grow alarmingly fast (he had tried to use this on Crabbe in the corridor, with very entertaining results); a jinx that glued the tongue to the roof of the mouth (which he had twice used, to general applause, on an unsuspecting Argus Filch); and, perhaps most useful of all, Muffliato, a spell that filled the ears of anyone nearby with an unidentifiable buzzing, so that lengthy conversations could be held in class without being overheard."

- Harry's use of the dark charms created by Severus Snape.

The Muffliato Charm (Muffliato) was a charm used to fill the ears of any person in the vicinity of the caster with an unidentifiable buzzing sound so as to allow long conversations without being overheard in a public place such as a class. The spell was invented by Professor Severus Snape whilst he was a student at Hogwarts School of Witchcraft and Wizardry

Hermione Granger originally disapproved of using the spell, but came to use it herself when it was needed; for example, to protect the campsites she shared with Harry Potter and Ron Weasley when they hunted for Lord Voldemort's Horcruxes between 1997-1998.

Known practitioners

 * Severus Snape
 * Harry Potter
 * Hermione Granger
 * A Hogwarts Charms Professor

Etymology

 * The English word muffle means "to make a sound less distinct by covering its source."

Behind the scenes

 * This is the last named Defensive Charm cast by Hermione before she begins her nonverbal spellcasting.
 * It is possible, given that when Harry Potter was shouting at his friends in an area that was protected by this spell and ravens flew up in shock when he began yelling, that the charm only works on humans.

Appearances

 * Harry Potter and the Half-Blood Prince
 * Harry Potter and the Deathly Hallows
 * Harry Potter and the Deathly Hallows: Part 1
 * Wonderbook: Book of Spells

Notes and references
Assurdiato Muffliato