popping noise

The heating and cooling of the porcelain and steel, or the movement of electric elements in their mounting brackets, in the oven may result in popping/cracking noises coming from the oven.

This is normal.

Sometimes a dirty oven with grease can cause this also, when the left over grease heats up it will pop just like if it is in a frying pan

Also its made of steel and porcelain so as these materials heat up and cool down it can expand and contract them creating a popping sound.

As long as it functions normal you should be ok