Light Switch Making A Buzzing Noise
If you have a light switch making a noise, that is not normal. A buzzing or popping noise suggests a problem, most likely with a connection either from a wire to the switch, or in the switch itself. Remember, most switches are plastic, with a small amount of metal at the connections.
If you have a loose or broken connection, you are probably generating heat at that location. The noise is likely from this loose connection and the danger is heat buildup and possibly fire. Try touching the switch or even the switch plate. Does in feel warm or hot? Even if it isn't warm to the touch, you need to investigate the problem.
Turn off the power and pull the switch away from the junction box. Check where the wires connect to the switch, as they might be loose. You find this a lot if the wire is pushed into the switch rather than wrapped around the terminal. I prefer to wrap the wire clockwise around the terminal and tighten snugly with a screwdriver. The other option is to simply push the wire into the terminal hole at the rear of the switch. This style is not as secure as wrapping the wire around the terminal screw.
If everything looks good, so far, I would recommend replacing the switch. I've seen 5 year olds slam their hand against a wall switch and crack it. Spend the $2.00 and buy a new switch.