DIAGNOSIS Yes, that's completely normal and a sign it's working correctly. You're hearing the refrigerant (the cooling fluid) circulating through the coils inside the walls. It's most noticeable when the compressor first kicks on or during a defrost cycle.
FIX No fix needed—it's just the sound of operation. To minimize the noise perception: 1) Make sure the fridge is level. Use a small carpenter's level on top and adjust the front feet by twisting them. A wobbly unit can amplify vibrations. 2) Ensure it's not touching the wall or cabinets on the sides, which can act as a sounding board.
IF THAT DIDN'T WORK If the sound changes to a loud buzzing, clicking, or grinding, that's a different story. A loud buzz that doesn't stop could mean the compressor is stuck. A rapid click usually points to a failed start relay. In those cases, power it off and call for service.
HEADS UP You might also hear a faint 'click' every so often. That's the thermostat or a relay switching the compressor on and off. The gurgling and occasional clicks are the soundtrack of a functioning fridge.