The part(s) or condition(s) listed below for the symptom Microwave is loud or noisy are ordered from most likely to least likely to occur. Check or test each item, starting with the items at the top of the page.
The magnetron uses high voltage, high current DC power to generate the microwave frequency that cooks the food. Under normal circumstances, the magnetron emits a low hum. However, if the magnetron is damaged or nearly burned out, it may begin emitting high-pitched sounds or growling noises. If the magnetron is noisy, this indicates that the magnetron is nearing the end of its life or might be defective. A defective high-voltage diode can also cause the magnetron to be loud. Before replacing the magnetron, first test the high voltage diode. If the diode is not defective, replace the magnetron. (Warning: The microwave oven can store a lethal amount of electricity in its high voltage capacitor, even after the microwave oven has been unplugged. Due to the high running voltage and the potential for electric shock, it is extremely dangerous to replace the electronic components in a microwave. Only a licensed technician should replace the magnetron.)