System sound with alot of text.

I have my share of experience with computers and hardware, but this one got me wondering.

I was installing GNOME on a remote server of mine and noticed when the text in the Putty window was scrolling by (quite fast) my laptop made a noise, not annoying or loud, just a slight noise, almost like a quiet tick.

I thought, that's strange it only makes that noise when i have putty up. I click the scroll bar to stop the scrolling of text and it stops. I let go and it starts, wonder what that could be. It's not the hard drive, this doesn't log any files, and its not a hard drive noise. Its not the fan, that's constant, does the CPU make noise? I have never heard a CPU, much less try to listen to it.

Does anyone know why it makes this noise, is there some hardware that's making the noise as it processes the text?