On low, in complete quiet, my L2T buzzes. I'd never heard it before. In addition to my L2T, my FL 712L, Argo HP, and Gladius buzz. The Argo HP is by far the loudest, the 712L is noticable with little effort, and the Gladius is very nearly silent (I could barely hear it).
I don't mean to offend anyone, but it could be that some of you can't hear your lights buzzing because you're too old. The buzz is a very high frequency, and those are usually the first to "go." One retail store somewhere used high-frequency noise as a teenager-repellant so that the older patrons could shop in peace. You can download a cell phone ringtone of a high-pitched buzz, so that only teenagers can hear the ring (and older people, such as some teachers, for example, cannot).