ClearerCast plays the Clearcasting sound when your druid, mage, or shaman gains the Clearcasting buff.
Move the included ClearerCast\Clearcasting_Impact_Chest.wav file to World of Warcraft\Data\Sound\Spells\Clearcasting_Impact_Chest.wav (if the Data\Sound and Data\Sound\Spells directories do not exist, create them) to silence the client's built-in sound, which is played whenever anyone around you gains the Clearcasting buff.
The combination ensures that whenever you hear the Clearcasting sound, you, rather than some other caster in your party, have the Clearcasting buff.
[1.1] Comaptibiltiy with Patch 4.1.
[1.2] Compatibility with Patch 4.3.