NOTE sound without a visual notification

Hi darko118,

Welcome to Apple Support Communities. The quickest way to identify any apps or processes that are running would be to check out Activity Monitor. Use the guidance from View information about Mac processes in Activity Monitor - Apple Support to view open apps and processes. You can even quit a process and then test to see if the same occurs. That may isolate the issue to a certain app or process.

Safe mode can help isolate this as well. Safe mode will prevent some apps and processes from loading up so that you can narrow down the issue. Use the following guidance from How to use safe mode on your Mac - Apple Support to access safe mode. As mentioned in that same article, if the same does not occur in safe mode, check and remove login items as they may be the source of the sound you're hearing.

"Apple silicon

1. Shut down your Mac.
2. Turn on your Mac and continue to press and hold the power button until you see the startup options window.
3. Select your startup disk, then press and hold the Shift key while clicking “Continue in Safe Mode.”
4. Log in to your Mac. You might be asked to log in again.

Intel processor

1. Turn on or restart your Mac, then immediately press and hold the Shift key as your Mac starts up.
2. Release the key when you see the login window, then log in to your Mac. 
3. You might be asked to log in again. On either the first or second login window, you should see ”Safe Boot” in the upper-right corner of the window."

All the best.