Popping sound?? or is it a clicking sound? The switches on your stove are called infinite control switch. They are a current matching device that actually turn power off to the burner when current is matched to setting number. This is normal. The sound is the switch turning itself off. Break one apart and you will see a thin piece of metal with small gage wire wrapped around it. It is this piece of metal warping to open and close the contacts that you hear.

Could be the switch arcing. If it continues the switch will burn out and need to be replaced. You can get a new switch from an appliance parts store for between 50 and 60 bucks. Just write down the model number of the range, get the new switch then swap the switches out one wire at a time so you make sure you get them right. The switch is usually held in place by two screws.