Some models of heaters will make certain sounds, which are normal. For example Radiant, Parabolic, Quartz, and Baseboard heaters will have a crackling or vibrating sound coming from them when they are first turned on. This is caused by the heating elements expanding as they heat up which is normal. NOTE: If you feel heat on all the heat settings then the heater is working properly as an element would both heat up and produce heat or not work at all.