You did not mention any cooling problems in the refrigerator or freezer. If you have no cooling problems, then the popping sounds could be normal operating noises. This model will make some cracking or popping noises at times when:
The defrost timer snaps into or out of the defrost cycle
The freezer control starts or stops the compressor
The evaporator cooling coils expand or contract during the automatic defrost cycle
Condensation drips down onto the defrost heater during the automatic defrost cycle
If you hear a different type of popping noise or have cooling problems in the refrigerator or freezer, resubmit your question with additional details for more help with this problem.