Wasn't certain where I should post this, so if it's in the wrong group I
apologise.

More of a quest for knowledge than being a technical issue, but I wanted
to know why when I am say editing photos, or moving text/picture boxes
in Word, etc. Do I hear a quiet hissing noise come from my computer?

It only seems to be apparent to me when I'm moving a 'block' of visual
data if that makes sense. Say if in Photoshop I was moving a layer
around, the noise would become apparent ONLY when I was moving the layer
on screen, as soon as I stop the noise ceases.

It's not the display or the speakers as it continues to do it with them
both switched off.

Would just be very interested on anyone thoughts.

Thanks.