Buzzing Dimmer or Humming Lights? Here's What's Going On

The short version

Dimmers don't lower voltage like a valve — they chop the power on and off 120 times every second, keeping the lights off for a slice of each cycle. That chopping makes small parts vibrate: filaments in old bulbs, driver components in LEDs, and a tiny choke inside the dimmer itself. Vibration at that frequency is a hum or buzz. Mildly annoying, mostly harmless.

Fixing the harmless buzz

Work through these in order — most people stop at step one or two:

1. Swap the bulbs. Cheap LEDs are the #1 source of dimming buzz. One quality "dimmable" LED from a major brand, tested in the same socket, tells you instantly if the bulbs are the problem.
2. Match the dimmer to the load. If the dimmer predates your LED bulbs, replace it with an LED-rated model (CL or ELV types). Modern dimmers are dramatically quieter with LEDs and eliminate flicker at low settings too.
3. Don't overload it. Dimmers carry a wattage rating (usually 600 W, less when ganged with other switches under one plate). Overloaded dimmers buzz louder and run hot.
4. Check the minimum load, too. A big dimmer driving one tiny LED can misbehave at the bottom of its range — hum, flicker, or ghosting. Raise the low-end trim (many LED dimmers have an adjustment) or use a dimmer designed for low loads.

The two buzzes you never ignore

1. Buzzing from anything that isn't a dimmer. A standard toggle switch, an outlet, or the breaker panel has no business making noise. Buzzing there usually means arcing — electricity jumping a loose connection — which is a fire mechanism, not a nuisance. Panel buzzing sometimes turns out to be a failing breaker; either way, it's a prompt professional visit.
2. Buzzing plus heat or smell. Any device that buzzes and is hot, smells like hot plastic, or shows browning has moved from physics to failure. Turn off the circuit and get it replaced.