What is wrong with my laptop charger and computer?

When I turn my laptop on plugged into my charger, it starts to make this screeching high pitched piercing noise that drives me freaking INSANE! It stops when I unplug it but it almost sounds like its still there when I put my ear down to my keyboard and I listen really closely but I can't tell. Maybe it's just my paranoia towards it. Is there something wrong with my laptop or charger or BOTH?! Should I invest in a new one of either?