The Buzz Surrounding Those Dimmer Switches

Question:

Hi (great website!),

I have a minor but irritating problem with 2 light dimmer switches in my home. When they are turned on (at any level), the fixtures (or incandescent bulbs) emit a soft but high pitched hum/buzz that I find excruciating (and no, I'm not a bat). Any ideas on what may cause this or if it can be fixed short of replacing the switches?

Thanks,

M. Welter

Reply:

This is an interesting problem. I have experienced it myself, but I heard the sound from the light bulbs more than the dimmer switch.

Apparently what happens is the dimmer switch uses a special circuit to pulse the power on and off very quickly. This pulsation causes the filament in the light bulbs to physically vibrate and make a high-pitched sound.

When the light bulbs are clearly the source of the noise, the solution is simple: change to a higher quality bulb with a heavier filament. This generally means replacing a plain ordinary type A bulb with a halogen bulb of a similar wattage. Supposedly halogen bulbs have heavier filaments and they don't vibrate when the power is pulsed.

Also, Rough Service bulbs (the kind used in trouble lights) may have a heavier filament and make less noise.

Fluorescent bulbs don't have a filament, but you cannot use them unless you get a dimmer that is specifically designed for fluorescents.

If changing the bulb type doesn't solve the noise problem, then the only solution would be to replace the dimmer switch.

Bruce W. Maki, Editor.