Why wouldn't this work...

A button attached to the back of the steering wheel to mute the empeg and enable voice recognition whenever you want to talk to it?

This would solve the problem of voice control when the empeg was at high volume, might allow effective use of an inexpensive microphone, and would also eliminate the possibility of unwanted voice commands affecting the unit... "I tell you, Bob, this here empeg is really loud compared to my old stereo ... what the... owww, that hurts, turn it down."

tanstaafl.

"There Ain't No Such Thing As A Free Lunch"