I have electric heat in my second floor bedrooms. Each bedroom has it's own heater and thermostat. They are all quiet except for the master bedroom. It creaks whenever it heats or cools. Simple you say. That's what I said 15 years ago when it started. I just replaced the heater with a new one. After a couple of weeks, it started again! I had someone adjust the screws holding the heater to the wall. No difference. I pressed on different parts of the heater, it made short term improvements but would creak again. I replaced the heater again, and the thermostat too. Quieter for a couple of weeks again, then it was back. Last winter, it creaked quietly. This season, I am being awakened by the noise. I can't go through another New England winter without a good night's sleep.