Long time reader, first time poster...
I purchased my droid the first day and was totally in love with it. Unfortunately, my girlfriend was not as impressed as I was. She used to complain (frequently!
) about my voice sounding muffled on the phone. I was desperate to find a solution and I found it in the thread below. I changed the vocode setting to EVRC-B and she immediately noticed the difference in voice quality. She has not made any negative comments about voice quality in weeks!
I would suggest reading the entire thread so that you are aware of the potential implications associated with changing the vocode settings.
https://supportforums.motorola.com/thread/17480?start=0&tstart=0
Good luck!