Ok, I have tried covering everything from the side notches/slits to the lower part of the keyboard, to the Sprint Logo on bottom to the entire bottom of phone with my hand all while recording a message to myself to see if I can hear a difference in any of them...and...I don't...grrrrrr.
The Krussel Glove Fit case I have has a small cutout that lays where the Sprint Logo is, but obviously isn't quite the right spot due to the muffled sound I apparently produce with this case on.
I must say that RIM did a stupendous job on hiding the microphone slot/hole!!!!
Again, this is the 7130e and I'm still at a loss on where my microphone is, even with the wonderfully helpful responses I have already received on this page.