The lights in our house that are controlled with dimmer switches all seem to have a faint buzzing sound when turned on. Does anyone know why this is?

The lights in our house that are controlled with dimmer switches all seem to have a faint buzzing sound when turned on. Does anyone know why this is?
Quite common, especially when the dimmer is set to low intensity. It is due to the internal circuitry in the dimmer and it might be possible to purchase a more sophisticated (expensive) model that eliminates this.

The buzzing is caused by something vibrating from switching the current. Check where the buzzing is coming from, and see if you can find something buzzing. Do not touch hot wires. If you can find the source, you may be able to stop it with a bit of glue, crimping with pliers, a wedge, etc. Too much glue can insulate a circuit leading to overheating and maybe fire. The vibration may be inside something not designed to come apart.