ACD noise

I have both 20" and 23" ACD for several months now. They don't make noise that I can hear. I know they should not make any noise. If so, there should be something wrong with your unit or precursor for something which may go wrong not in the distant future (usually a day after ACD's 1 year warranty is up). If mine is making noise, I will call up Apple for the warranty repair.

is it a constant whirring or does the pitch change? is is more of a popping of a buzzing?

there may be faulty connections, or the unit is running in an obscure way, eg at a higher power level than normal....have you tried a different wall socket?

does the display have any visual signs of poor performance? do all the USB ports work? are all your cables firmly plugged in?

if the answer is yes to any, call apple pronto.

Mine blew up when it made noise. Take it right back.