I think it’s from the logic board heating and flexing, as the pops occur for me once I put the computer under heavy usage.I was on High Sierra for a long time, just upgraded to Ventura hoping it'd fix the pop sound, but no.
there are other sites describing the same symptoms and no one has gotten to the bottom of it. I remember paying over 2k for this machine and now it is not even worth $400. Plus I won't be able to sell it with this pop issue.