Jerson has a point.
Unless you are storing or reading from memory digitizing isn't required as the mic and speaker are both analog.
Also much more bandwith required for digital transfer.
Analog is roughly either amplitude modulation (AM) or frequency modulation (FM) which is just a signal where as digital requires many bits of information depending on the resolution whether it be 8 bit or 16 bit.

I you wish to digitize however I have a very complete example of reading audio posted at PIC iPod wav player

I started with just a mic to a preamp to an amp to a speaker.
From their I digitized the pre amped mic signal on a PIC and then returned the signal to analog then to an amp and speaker with the same PIC.
Wired or wireless transfer of the digitized data between 2 PIC's would be next.

Audio is cool because you can hear the results.


Norm