I did some research online... Now, I don't recommend anyone actually go into the programming menu of your phones, if you do so it's at your own risk...
That said, to fix the Motorola Droid muffled voice problem:
- Dial ##PROGRAM (which is ##7764726) and hit send
- Enter 000000 as the password and click Verify.
- Go to Vocode and Change it from EVRC to EVRC-B. Apply this, and exit the programming menu.
Your phone will reboot, and hence forth, sound much better to those you're calling.
This information is offered with no support, warranty or any sort of promises.