There can be several reasons why your new LG microwave makes noise when it starts up or stops cooking/heating food. While it's difficult to pinpoint the exact cause without more specific information, here are a few possible explanations:
Fan noise: Microwaves often have a built-in cooling fan that helps regulate the temperature of the internal components. This fan may turn on when the microwave starts and continue running for a short period after the cooking process is complete. The noise you hear could be the sound of the fan operating.
Magnetron noise: The magnetron is the component responsible for generating the microwaves used for cooking. It is normal for magnetrons to produce a humming or buzzing sound when they are operating. The noise may be more noticeable when the microwave starts or stops cooking.
Relay switch: Microwaves use relay switches to control the power supply and turn the magnetron on and off. The operation of these switches can sometimes create a clicking or buzzing noise during startup or shutdown.
Turntable noise: If your microwave has a rotating turntable, the noise you hear could be related to its motor or mechanism. The turntable motor may produce some noise when it starts up or stops.
Ventilation system: Some microwaves have ventilation systems that help remove steam and odors during cooking. The noise you hear could be related to the operation of the ventilation fan.
It's important to note that some level of noise is normal for microwave ovens. However, if the noise is unusually loud, persistent, or accompanied by other issues such as sparks or malfunctions, it may indicate a problem with the microwave. In such cases, it's recommended to contact LG customer support or consult the product manual for troubleshooting steps or to request assistance.