Just read a TidBITS article about iPhone 4/4S microphones. When held to the face in “normal” phone mode, the main microphone is at the bottom of the phone and the top microphone (small hole near the headphone jack) is used for noise cancellation. When in speakerphone mode, only the top microphone use used as the bottom one would cause excessive feedback.
So, what mode and which microphone is active when we are using Waze voice commands? I have no idea.
Why would the microphone need to be active? am i missing some feature? are you talking about the bluetooth ability and linking to your car speakers?
The iOS version in North America has a voice recognition feature for doing simple tasks like reporting traffic!
As an Android user outside NA I expect to get this feature somewhere around summer 2014!
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Alan, was wondering the same thing 
so did a little testing with it, it seems that the only mic that works on my 4S is the lower one in waze mode.
Putting your finger over the top one and activating the voice commands, it hears everything I say, but when holding fingers over the lower one it keeps asking me to repeat myself.
Nice, Dakender! Thanks for looking in to this.