So ive been having this problem where people Im talking to on my handset struggle to hear me. The sound is either muffled or very quiet. This has frustrated me to boiling point but Ive recently discovered a few posts on XDA linking me to the following blog. Fix For Low Microphone Volume On The Samsung Galaxy S II : Ctrl + Z Worked wonders for me. NOTE: Sadly this "fix" resets after a reboot and would require punching in again.