1. open dolphin, select any file/folder and press shift+del to delete. Dialog to confirm deletion appears and plasma plays a notification sound 2. cancel deletion dialog and close dolphin 3. right click the sound icon in the system tray, select "Configure audio volume" 4. click "audio volume" section, "applications" tab 5. click the sound icon to mute the notification sounds, click "ok" button 6. repeat the step 1: the notification sound plays again 7. Reopen "Configure audio volume", "audio volume" section, "applications" tab: sound icon indicates that the notification sounds are NOT muted. Tested with plasma 5.13, phonon-qt5-gstreamer 4.9.0-4 and phonon-qt5-vlc 0.10.1-2 on Arch linux.
my own duplicate lol *** This bug has been marked as a duplicate of bug 398392 ***