This is a single 0 byte file with a .ogg extension contained in the appropriate folder structure that overrides (and mutes) the sound made by male Orcs NPCs laughing.
To install it, just extract the downloaded zip and copy/paste the Sound folder into the main WoW directory. If it asks if you want to merge folders, click Yes. Do not install via the MMOUI Minion or Curse Client as they will try to install this as an AddOn (which won't work).
Thanks to Dliver for posting this thread asking for a way to mute the sound and for testing whether I'd found the correct sound file.
This also mutes the male Orc player character laugh emote, since most male Orc NPCs use the player character's laugh sound.