One on the KDE Desktop system that I like is look beauty with sound notification when you open/close or anything else notify with KDE Application. Say that when you work with email client you can configure to notify when mail coming or notify on you when battery critical empty. So, if you feel boring with old sound you can change that with little bit configuration on Configure Desktop.

First, you can find configure desktop (in this I’ll try on KDE 4.2) on application launcher at left bottom:

After left click on configure desktop this window viewed on you:

Click on notification icon and a new window viewed:

now, you can change sound application on bar application > Event Source. For example on KDE system notifications sound login you change the old one with a new sound.

on the words play a sound, click on diskette icon and browse,select a new sound file. Thats it!

Good Luck!!