Hi Paul, here to help.
To turn off system sounds in Windows 11, follow these steps:
Right-click the Speaker icon in your system tray (bottom-right corner).
Select "Sound settings".
Scroll down and click “More sound settings” under Advanced (this opens the old Sound control panel).
In the Sound window that appears:
Go to the "Sounds" tab.
Under Sound Scheme, select “No Sounds” from the dropdown.
Optionally, uncheck “Play Windows Startup sound” if it's enabled.
Click Apply, then OK.
Done! This disables all standard Windows alerts like notifications, pop-ups, errors, and more.
Let me know if you still need help with anything else.