And now I understand why my British colleague and I found that noise particularly annoying in the US: the frequency was lower there, and therefore probably seemed louder than what we were used to in our home countries (Australia in my case). Our boss, who was older and thus probably couldn't hear it, didn't understand what we were complaining about. (P.S: I'm in my mid-40s now, so my vision is seriously deteriorating, and I'm missing that a lot more than high-pitched monitor sounds. So enjoy that while it lasts, too.)