why do my lights make a buzzing sound when using dim control?

[Imdmn04]

I have lights with a dim control installed, when my lights arent fully lit, there is this buzzing noise, not very loud, but u can certainly hear it, and its gone if i turn the lights all the way up at the brightest setting, why is that?

 

[Kadarin]

You know, every one of those floor lamps with the halogen bulbs that I've owned has done that exact thing.. (Not only that, but the dial switches on those things always break.)

 

[EY2K]

pulse modulation, it's the same kind of buzzing you experience when you turn the knobs on your vantec nexus fan controller.

 

[dighn]

i'm guessing because the pulse width becomes smaller the filament (or the gas surrounding it?) has more time to cool so there's enough thermal expansion/contraction to make an audiable sound.

 

[Kelemvor]

My ceiling fan does that too. If it's on the highest speed it's silent. If I pull the chain to the medium or slow speed, there's a loud "hum" noise. No idea why. You tune it out after a while and don't notice until you turn it off and it so much quieter.