Hello mingo,
with all respect I try carefully all those steps and even more and the sound from recorder or call phone, in speaker mode and phone mod, the result are the same, when I make calls, the other side people hear me clearly but, very very low volume like exist a potentiometer with volume to minimum also, the shop repair special for iPhone which do not work on Saturdays and Sundays says: (we try test of your microphone and all frequency are correct and if we replace the microphone and work low the same, you do not pay anything and I ask special that: my phone it is clean? and they says: yes is very clean).
The problem "I repeat" become from last first update with IOS16 and many of us, we talk about this subject even a lot go to replace the microphone and do not resolve anything about this problem.
Then, repeat master mingo, the other side of conversation with people can hear me very clearly but, very, very low also, when do test recorded on all 3 way, the microphones record very clearly but very, very low volume also, it happened with 14 pro and that come from when updates with IOS16.
Again, immediately after instal updates IOS16 appear this problem. The phone it's perfectly ok, always clean, no water because even I understand from factory, it's protected against water and shok, all cover was bought from Apple shop and the last is smart case battery which even that, I take out to do Test recorder and You know that case protect the phone, and none of another accessory was adid or replace just adid screen protection lsat year in Summer from the same, Apple shop in my presence because was faster and do not need to go ever for repair because I like to be always carefully with Apple electronics because I trust they are the best on World and components are made not in China but in Texas Instruments which is in U.S.
Regards,Mihai