Pot making popping noises
For me, the popping is most often from water.  It could be in your oil, under the pan, between the pan and a handle, etc.  In some pans there could even be more than one layer to the pan and moisture could have gotten between the layers.  In this case, I would tend to replace the pan.  Thin pans, especially those of aluminum, present another source though, they warp while heating.  For things like boiling, this is not a big deal, but such a pan I would not use for heating oil.  If a pan warps with hot oil there is a real potential for splashing or splattering which could result in burn or a fire.  Oil applications such as deep frying I stick to heavy pans only