Unless it's a manufacturing fault, I don't think an UPS should make any noise at all. Low-quality ones might buzz or whine, granted, but you get what you pay for -- unless you got ripped off.
Anyway, I've been using a PowerWare 3110 for years. Sure, it's big, only has those PC sockets and doesn't sport looks or modern features like USB control, but it does its job. And quietly. The only time I hear it is when it beeps after a spike or power loss, or when the batteries are starting to go. It's no longer for sale, but the follow-up model shouldn't be too bad I'd imagine -- and mind you, this is the cheapest bulk model that PowerWare offered.
I've also been pleased with what APC has offered me in surge-protected extension cords. Sturdy, reliable and lasted for years. We had some of their server UPS units at work and they seemed okay, just more gimmicks than the PowerWare plastic bricks.
I heartily recommend PowerWare and wouldn't mind using APC. Choose one with a long-time retailer in your area to guarantee flexible service and model availability.