This confused me when I went onto Linux and still got the windows noises. I will take a look at making some sort of sound or we could use one with appropriate licensing.

One of such sites to find licensed sound effects is https://pixabay.com/

The sound is the same used by outlook. I never know the time is up because I think I got a new email.

It would be nice if the volume can be controlled too, most of the times I have some background music playing & never hear the timer.