Since the last update, Amarok shows some dialog about something it could not do, on startup, I click OK, it goes away and everything is fine. Only, it also beeps with volume set to max. Is there a way to disable the beep? I could find neither a KDE-wide option that should work for Amarok too, nor a similar topic in the forum, or advice on google.

You can disable the system notification in the KDE system settings