It is not a system sound. It sounds likea relay click.
For example when I did a left click on "reply" there was a click followed a
few seconds later by another click. I currently have a laptop but I have
heard the same sound on all other PC (not Mac) computers within the
keyboard, not speakers.
This is not a problem. I am just interested in knowing what it is. I thought
that the entire computer was solid state so it is strange to hear a relay
click.