I'm sure the two APC UPSes we have at work can be told not to beep. However they are not exactly bottom end at 1500 and 2200VA.

Worse for us is our Dell PERC RAID card in our Poweredge server. It beeps when rebuilding a RAID5 drive. And that takes hours (something like 6 or 7 I think). When we first got it I decided to try out the hot-swap RAID5 capabilities and pulled a drive on it live. Wasn't very popular at work that day....