HUM : Microwave ovens also produce a hum. It comes from the transformer, diode and capacitor, which vibrate as they step up the 60-hertz electric power from a wall outlet.

• 嗡嗡声的成因：微波炉也会发出嗡嗡声。这声音是来自变压器、二极体还有电容，这些元件在提高至60赫兹的家用插座频率时会不断振动。