When KDE applications create notifications, the first notification is quite loud, and subsequent ones are quieter.

For instance, this bug happens each time I open System Settings.  When I modify a field and then switch to a different tab, the notification is loud.  Subsequent times, the notification is quiet.

This also appears to affect KDE's desktop's notifications.  The first desktop notification sound is loud compared to the ones following it.

While jumping out of my seat is a good way to keep the adrenaline pumping, for now I have disabled all notification sounds as a workaround :)