There is no way no one is hearing this rattling/crackling sound on the 15 lineup when above a certain volume level on some sound frequencies. Just went to an Apple Store and all iPhone 15s had it. The pro/pro max and regular/plus ones. I have it on my 15PM. Check this video for a comparison to an iPhone 14. It’s definitely a widespread issue, I guess, since more than 10 devices at the store had the exact same problem.
I went to an Apple Store and they ran diagnostics on my phone and said there is nothing wrong with it 🫤. What’s bizarre to me is that all iPhones at this store had this exact issue, which means it can’t be only my unit.