Phonoturgy

Phonoturgy is a form of magic that can create a cloak of silence.

Description
Spells to keep to dull sound and keep conversations private are basic tools for Wazards. They quiet any sound the user makes but it also prevents the user from hearing sounds by creating a sort of "sonic bubble". This can be dangerous because an enemy can sneak up behind him or her.

In the Series
In Changes, Harry uses it to silence his going up the stairs while following a group of vampires into his office building. The he turns it off so that he can hear where they are.