Lets you spam that spell without getting that "Burnout" of the spell because you are already casting it.
Copy the Sound folder to your "World of Warcraft\Data\EN**" folder.
** (this is your landcode, examples :GB ,US, etc..)
Examples (Presuming that you have installed WOW in C:\program files\World of warcraft)
C:\Program Files\World Of Warcraft\Data\enUS\Sound\Spells\Fizzle
C:\Program Files\World Of Warcraft\Data\enUS\Sound\interface