Strange SECOND "phantom" volume bar in Windows 10

I bought a new (refurbished) PC just recently. The strangest thing is happening with the sound. When I go into sound settings (right click on speaker icon, click "open sound settings"), and look at the volume bar, I have TWO volume bars. One blue, one dark blue. I attach you pictures to show you what I mean. One of the bars (the dark blue one) is wildly moving all over the place and behaves randomly. It seems to for some reason have a life of its own.

I also have a strange flickering sound in the background on the speakers. It won't go away. Also, when I trigger the windows "error" sound, the dark blue bar goes right up! Suggesting, it has something to do with windows-generated sounds. Indeed, if I go into wordpad and mash some buttons to produce the bell-like "error" sound, the dark blue volume goes right up!:

So my question is, what is the dark blue bar? And why is the dark blue bar moving autonomously all over the place with no input from me? Could it be the thing causing the strange flickering I hear in my speakers?

Solution 1:

It's the volume of currently playing sounds. It will be invisible when nothing is playing any sounds. You can look for the source of the mysterious constant sound in the volume mixer.