I have a problem with built-in microphone that my end is clean listening to the other participant but that person claims the volume is really low. I have the same issue when using bluetooth but if I use wired headset, quality is clear crispy. Before proceeding with fixing one or more parts through service centre, I wonder if you can help me re-calibrate mic. I got in the hidden menu and went to Device Test > Sound Test>Audio CAL Tool, then tried Sound Calibration and MicAmp Calibration and see if I modify anything to increase the mic volume. Does any one have experience with this and please let me know how to do this so that I can try to fix it at the software level if possible?