Question [Q] [Paranoid Android][HTC One m7] bad sound quality during calls

I got a HTC One M7 and since a few days I am running the latest version of Paranoid Android (that is 4.4 stable, not RC or Beta or something). Since I am using that ROM, people complain about a not hearing me well during calls. Furthermore they can hear themselves when I turn on the external speaker.

Both problems appeared with the ROM, I didn't have one of them while I was using MIUI, so i guess they are related to the software not the hardware. Does anyone have similar problems? And is there a way to fix them?

PS: If this is the wrong forum, i am sorry for that. My account is on noob-level, so I can't post to development forums.