Windows notification sounds while computer is idle and locked

I have a Windows 11 Personal machine that is driving me nuts.

When the computer is idle and locked, I randomly hear notification sounds, similar to a USB device being plugged in.

I've tried disabling all notifications and it still keeps happening.

This computer is left powered on all the time, and I randomly keep hearing these notifications from other rooms in the house.

Any suggestions appreciated!

Welcome to the forum. More often than not, the chime sound plays when a peripheral device is connected or disconnected from your computer. A malfunctioning or incompatible keyboard or mouse, for example, or any device that turns itself on and off, can cause your computer to play the chime sound. USB hubs and drives are often the culprit as well as usb printers. Other causes of chiming can be incoming emails or loss of scan to computer function.
Disconnect everything to see if the problem goes away. Then connect devices one at a time until you find the right one.

If the sound persists after all peripheral devices are disconnected, you can turn the sound off but this will not tell you exactly what is causing it. It will, however, give you more indication of what is making it happen. Right click sound icon in task tray>sound settings>more sound settings>sounds tab>
click the "Test" button next to each Program Event until you locate what event is causing the sound you are hearing.

If you choose, you can disable the offending sound by clicking the "Sound" pull-down menu and selecting "(None)." but it's best to find the cause rather than covering it up.