"Listening..." screen suddenly popping up on Android 6: what is it, how to disable? Every now and then, some Google "Listening..." screen pops up , like this:

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FYI: my device is a Nexus 5X with the latest stock Android 6

I have no idea what this is, and worse: I don't know how to get rid of this. It seems to occur when my earphones (not headset or mic, just earphones) are plugged in. But not consistently, I can't deliberately reproduce this.

Upon searching around I found some suggestions this may be related to Google Now or OK Google, but both are disabled already. 

How do I prevent this from ever showing up again?
This happens when you tap on the little Mic image In the Google search bar at the top of your screen on the right hand side of the field box.  It's the Google Now voice command interface.