starts listening when i sit it down

[WPCentral Question]

Just got the 8.1 upgrade on my 920 and I can't figure out what is causing my phone to start listening when i sit it down. Maybe 20% of the time when I sit the phone down on my desk (have not pressed the search button and certainly have not held it down) the phone starts listening. I will have it on the home page, press the power button to make it sleep, sit it down flat face up, then about 3-4 seconds later it wakes up and is listening for commands. Not a major problem but I am really confused as to what is causing this.