I'm using Cyanogenmod 10.1.3. As I understand the phone, the regular microphone is at the bottom edge on the keyboard part of the phone. There's another microphone (noise cancelling?) on the top edge near the power button. The speaker is the slot on the back. Does that have a microphone function too?
I recently replaced the earpiece like so many other people have. Could I have disturbed something near that top mic?
I was wondering if there's a way to test the mic near the power button.