The humming sound that you hear from microwaves and some other electrical appliances is typically caused by the vibration of certain components within the device. The specific causes of the humming can vary depending on the appliance, but here are some common reasons for the humming noise:
Magnetron (Microwaves): In a microwave oven, the most common source of humming comes from the magnetron, which is responsible for generating the microwaves that cook your food. The magnetron is a vacuum tube that contains magnets and high-voltage electrical connections. When it's in operation, it can produce a low-frequency hum due to the oscillation of the magnets and electrical currents.
Transformers and Inductors: Electrical transformers and inductors found in many appliances, including microwaves, can also cause humming. These components use magnetic fields to transfer energy, and the vibration of the magnetic core can produce the humming sound.
Fans and Motors: Appliances with cooling fans or motors can also generate a humming noise. The spinning motion of fan blades or motors can cause vibrations that produce the sound.
Vibration of Components: Some appliances have loose or poorly secured components inside. When the appliance is turned on and operating, the electromagnetic fields or air currents generated can cause these loose components to vibrate, resulting in a humming noise.
Electromagnetic Interference: In some cases, electromagnetic interference from other electronic devices or power sources can cause humming in electrical appliances.
It's essential to note that in most cases, a low-level humming sound from electrical appliances is considered normal and not a cause for concern. However, if the humming is excessively loud, irregular, or accompanied by other signs of malfunction (e.g., sparks, burning smells, or unusual heat), it may indicate a problem with the appliance that should be addressed by a qualified technician.
To reduce the humming sound in appliances, manufacturers take measures like dampening materials, better component design, and insulation to minimize vibration and noise.