Is rattling noise being heard over sound of ventilation fan and operating magnetron?
If the accessories inside the microwave oven cavity are improperly installed they risk coming
up loose when operating unit and create a rattling noise.
Avoid storing objects directly on top of the microwave oven or even leaning against the sides
of the unit. Objects especially such as glass, ceramic or metal will vibrate from magnetron
operating if leaning too close and generate a rather annoying rattling noise. Remove all objects
from the top and any from both sides if they happen to be touching exterior panel.