Why do microwave ovens hum?

Answer by  bl834 (1317)

Two possibilities: the fan that's cooling the magnetron, or the transformer assembly that's transforming the power from the wall outlet.

Answer by  champaign9497 (11977)

A microwave oven has a huge fan in it the fan in a microve is big enough to cool a full size refrigerator and freezer so when you turn the microwave on you hear the fan come on and it is loud because the microwave is small and the fan is huge and moving alot of air at one time.

Answer by  NutBucket (140)

Microwaves have convert 120 volt (low voltage) electricity into very high voltage electricity to run the microwave making thing. The transformer that converts from low to high is made up of lots of layers of wire and insulation that chatter because of the strong alternating magnetic fields caused by the electricity passing though it.

Answer by  worker76 (773)

Tehn humming that you hear when the microwave is running comes mostly from the fan that runs duering operation. The fan keeps a clean flow of air inside the microwave. Acts sort of as an exhaust fan. The heating element makes a little noise while running as well. mostly the fan though

Answer by  dr84bhl (2789)

The microwave hums because of the power relay. You should always hear the hum when cooking there should be a soft hum with intermittent sounds every five to ten seconds. The hum can be heard more on a high power setting. The power relay is what drives the microwave and makes it work.

Answer by  LeheckaG (1826)

Microwave ovens have a cooling fan & electric motor which is the source of most "humming" noises/sounds. The other possibility is if something like: an oscillator or power transformer is mechanically loose; the 60 Hertz electro-magnetic vibrations, and their harmonics can also cause an audible "humming" noise or sound.

Answer by  Liz59 (10966)

They may that sound because they are circulating air from within. All microwave ovens make this sound due to the transmission of air. Also, keep in mind that it is working at high temperatures and experiencing this degree of noise is perfectly normal. It is a good thing to be able to hear your microwave working.

Answer by  ladybud (1069)

Few thing's make's them hum are the cooling fan's that cool the ballast and the ballast also hum's. The motor to turn the tray if one is available will hum.But 99.5% humming is from the ballast.Microwave's run on same kind of ballast a street light run's on and the hum is exact same noise.