Product name/model: RT210WM2110
Causes:
1. Shrinkage and swelling of case will make such a sound; when the case is cold or the door is opened, this sound will occur phenomenon: there is a "hum" sound in the refrigerator).
2. Running of compressor will make such sound, if the refrigerator is not leveled, this sound will be louder.
Remedy:
you should consider to level up the fridge to avoid the noise.