The dimmer switch on my living room wall occasionally makes an annoying buzzing sound. I figured-out how to solve the problem using a small magnet.Most dimmer switches contain an inductor wound on top of an iron or ferrite core. This coil acts as a "choke", to smooth the pulses of current generated by the dimmer circuitry. The buzzing sound comes from the bucking of the magnetic field in the choke coil. There must be some ferromagnetic materials in the switch and its housing that become slightly magnetized over time and vibrate in sympathy with the pulsed inductor.
I found that I can eliminate the buzz by passing a magnet near one of the screws. I used a segment from one of those "ball and stick" magnetic model kits, which is a small but strong rare-earth magnet (probably neodymium). The small magnetic bias inside the switch is disrupted by the magnet, and it falls silent. If the buzz returns, I just bring a magnet up to the switch again, touch it to the bottom screw, and *presto*, the noise is gone!
