Stop Cortana responding to "hey"?

I've had Cortana pop up and listen with music playing, when I'm talking, singing along with music and once when I was on the phone!

dalchina said:

LOL!!!

dalchina said:

Ok, so you have the Creator's Update; formerly, did you have the Anniversary build (1607) and if so, was Cortana ok then?
Also have a look here
Attachment 133586
and check your microphone levels (I'm wondering about clipping and distortion). (Green bars)

I've not seen any other reports of this problem...

I don't know what build I used to have but I only recently turned on Cortana so I also don't know whether it would have worked properly earlier.

When I'm playing music, only the first one or two green bars light up; it's nowhere near to clipping.

Here's a screenshot with just 'hey' in the box instead of 'hey Cortana': http://imgur.com/msMpzXA.png

It also activates with nothing in the box at all, as though I'd pressed Windows + C (which of course I didn't).