This morning when I came into my office, one of my UPS's (uninterruptible power supply) that was attached to a server and a hub was making a really obnoxious noise like a high pitched whine.
Since the servers are necessary in the function of my business, I always keep a spare battery backup here just in case one has an issue and I can switch it out so my servers are always protected against turning off during a surge or power outage.