DIAGNOSIS That's the sound of the compressor's inverter board relays clicking. It's normal operation for this model.
FIX No fix needed. The inverter compressor modulates its speed to maintain temperature, unlike older units that just cycle on/off. The clicking relays are part of that process.
IF THAT DIDN'T WORK If the clicking is accompanied by a failure to cool or an error code, the inverter board or compressor may be failing. Unplug and contact LG.
HEADS UP The noise is most noticeable in quiet rooms or at night. It's not a defect, but a characteristic of this specific inverter system.