Hello there, if you are sick of hearing some dhead's mechanohog or a priest's "Inner Focus" playing constantly in the background, you can "remove" the game files. Well you are not really removing anything from the core client, but replacing it with your custom patch. Kinda like the new models you have in the HD client.
1. Start it up and select "Open MPQs"
2. Navigate to your client folder into /wowclient/data
3. Select all the MPQ files and be sure to check "Merge" in the next dialogue
4. Look for the file you want to replace (most of the time is invested here :')
5. Extract that file and edit in any audio editing software (I used Adobe Audition and just decreased the volume until nothing is heard)
6. Create an MPQ file where the path to the audio file is the same as in one of the MPQs you orinally found it.
7. Name it patch-X where X can be 5 to 9 or a to z (like patch-u.mpq or patch-7.mpq)
8. Place it in the same folder as your main MPQ files.