During defrosting, there will be noise, such as:
1. “hissing” sound :
ØMelt water dripping on the defrost heater during the defrost cycle.
2. “popping” sound
ØDuring defrosting, the temperature of the pipes and internal evaporator changes, they will expands and contracts
3. “tick” sound
ØDuring the defrost, water draining from the freezer section will drip into the tray in the freezer compartment or the back and bottom of your refrigerator.