How is this even possible?

Sometimes when I have my ear buds plugged into the speakers and scroll the wheel on the mouse, I hear static. Only when the wheel is moving. I also have a whinny power supply. Even when the computer is off I hear noise. I red that some PSU make noise when displaying 3D objects, could it be a simillar situation? I have a UPS which the computer and speakers are plugged into.

are the mouse and the earphones both plugged into the front of the computer? or both the back? plug one into the front and one into the back and see what happens...it sounds like the PSU may be dying which may also be causing your problem with the mouse/earphones, like the PSU might not be supplying enough power to whichever side of the PC you are using. Of course, thats just speculation from me, I cant be sure of anything.

Both are connected to the back but it's not happening now. The mouse is wireless btw.

idk, I doubt its possible but perhaps the scroll "signal" was causing some interference..normally its between 2 wireless devices instead of 1 wired and 1 wireless..idk. just speculating again.

I think it happens when my external hard drive is on (btw this thing is ancient)

It's hard to tell when this happens. I was scrolling along Facebook and the noise was happening and I turned off my external hard drive and it didn't fix it. I closed and opened Firefox and the noise went way. It only happens with my ear buds when I unplug them from the speakers the speakers have no static noise.

Oh I just turned my hard drive back on and noise happens when I scroll. But after posting that sentence it stopped. And now it started again, no joke.

It only happens if I can actually scroll, for example if I'm on the desktop and scroll nothing happens and no noise is made.