DIAGNOSIS Two possibilities. The gurgling is normal refrigerant flow. The buzzing is often the evaporator fan motor hitting ice buildup or a failing fan bearing.
FIX For buzzing: Unplug the fridge. Let it defrost completely for 24 hours. Plug it back in. If the buzzing is gone, the issue was ice on the fan. Ensure you're not holding the door open too long, which introduces humid air.
IF THAT DIDN'T WORK If the buzzing returns after a full defrost, the evaporator fan motor is failing. It's located behind the back panel inside the freezer. Replacement requires disassembly.
HEADS UP The gurgling and hissing sounds are normal operation of the refrigerant. Do not mistake them for a problem. The buzzing is the issue to address.