What would make a leviton dimmer switch make a buzzing noise?

Some of the noise depends on the circuitry of the dimmer and how the electricity is regulated. Does the buzz change with different light levels? Disappear when at full light? What wattage are you running and is this a standard 600 watt dimmer?

Add the total wattage up on all the bulbs in that fixture.As long as it's not over the usual 600 watts you should be OK, but I've seen people buy dimmers and use them to knock off 2 birds with 1 stone ( dimming the light and adjusting the speed of a fan.) That's a no no.. But the way, on every light socket there's a label that tell's you the max wattage for each socket. Don't exceed it.. Also it's the nature of the beast for dimmers to become warm and hot to the touch from the wall plate.. More wattage-more heat..

I have the same question and didn't see an answer here. I am running under 250 watts on a switch good to 600. And yes, it only buzzes when not at full brightness and is quiet when turned up but the point of the switch is to use it at lower levels.
Thanks in advance for anyone's thoughts.

That has been a noticeable problem when at low load. Not sure why. Some people indicate it is due to some bulbs. Have you contacted Leviton customer service?

I found the problem after I posted this. I was a high efficiency bulb in one of the fixtures, I replaced it with a different type and buzz is gone. I hope this help someone else.

Thanks for the response.