Gah! From alarms, beepers, universal power supplies (UPSes), etc. Especially with low batteries or something else. It is even worse when there are so many devices using the same loud high pitch beeps. Argh. It took almost three days for your overlord and others to figure out its source. It was a frakkin' beeper/pager due to its low batteries to whine every hour, exactly at X:05 time (five minutes late compared to the atomic times/clocks)! Ugh. :(