SUMMARY If you set system settings - audio - system notification sounds - to zero, KDE still beeps for notifications (e.g. on deleting the wastebin). The only way to turn off the notification sound properly is to unmute then remute the setting. This has been a bug for seven years, see: https://unix.stackexchange.com/questions/213285/how-to-disable-event-sounds-in-plasma-5 SOFTWARE/OS VERSIONS Linux/KDE Plasma: (available in About System) KDE Plasma Version: 5.24.4 KDE Frameworks Version: 5.92.0 Qt Version: 5.15.3
I can't reproduce the issue. When I mute notification sounds with the mute button or set the slider to 0% volume and then empty the trash, I hear no sound. This points to the issue possibly being caused by a deeper level of the audio subsystem than what we provide in KDE.
It might happen only on a fresh install
*** This bug has been marked as a duplicate of bug 425974 ***