Google search not responding to voice command?

[PhobicCarrot]

I am trying to find a useful system for use in the car, and the S Drive functionality is horrible, as it requires too much physical interaction with the phone.

I was playing around w/ Google Now and discovered the ability to activate it w/ voice by saying "Google" when the app is open. However, I cannot get it to respond. (I did make sure the "Hotword detection" box was checked.)

Suggestions?