I just got these headphones, but notice that the microphone would pick up almost everything, constantly. Even on teamspeak, using push to talk.
Scoured the net, and found this:

http://superuser.com/questions/700937/hear-myself-in-asus-orion-pro-headset

The solution is in the first post.

I found muting the sidetone slightly weird, so I have set mine to 1, and it is much better.
Still need to fine tune to find my sweet spot.

Hope this helps guys.