I can not reproduce the starting point because I was not directly affected. More or less since SFOS3 my call partners started to complain about the audio quality of my voice. I tested it against me and I was surprised about the very bad quality. I tested the wired headphones of the phone (Xperia 10) and I bought a JBL and Sony wired headphone (on-ear) with mic. All three wired headphones produces bad audio quality while speaking with call partners. The same headphones have no issues on my laptop the mic input of all three wired headphones are totally okay. So, the only “hand-free” method making calls is using the build-in speakers and switch from internal to external loudspeaker.
I wonder If someone have the same issues with wired headphones?
PS: Tests with sailfish-audiorecorder shows the same quality differences.