05 OEM nav Addition with Bose and no Onstar

[corvettezman]

I have a 05 with the Bose and HUD but no Onstar, I have an 05 NAV unit coming off fleebay to replace my 6 CD changer.
I already know about how to replace the unit, install the antenna, and the Tech2 .
Now the question is :
since I don't have Onstar, I don't see a Mic anywhere in the car ... Why would a Nav unit need a Mic ? or does it ? If it does , is it pre-wired in the car ? and location of mic?

thanks

[bub]

Mic is for voice command feature of nav...

Mine is in the A-pillar.

I have no idea if it is prewired in all C6's.