Where is the sound file of Installer success stored?
The file you are looking for (on El Capitan) is located in: /System/Library/Components/CoreAudio.component/Contents/SharedSupport/SystemSounds/system/

Specifically, the file is burn complete.aif (or burn failed.aif, they're identical).

Older versions of OS X (unknown when it changed) have it at (source):
/System/Library/Components/CoreAudio.component/Contents/Resources/SystemSounds/system/