steve817
TPF Noob!
Kent Frost said:USM stands for Ultrasonic Motor, which means that it's virtually silent. Very handy when you're taking pictures of weddings, for example. You won't disturb the ceremony. Oh, and they're mighty quick, too. ;-)
Yes they are very quiet, just bought a couple of them last week got home and took the first one out of the box to play and thought it was broken because I couldn't hear it.