This contains a few blanked (0 bytes) files for the Tortollan Seekers (Nola, Kojo, Toki), that silences all the NPCs specific VoiceOvers.
This should be unzipped in the root directory of "World of Warcraft", so as to the "Sound" folder gets created directly next to Wow.exe.
As of 8.2, this functionality has been removed from the game. You should use the new API via an Addon or whatever: https://www.curseforge.com/wow/addons/mutesoundfile