I cant see any mention, but mine does work (of sorts). The Realtek driver installs it and if you pump everything up to max then I can just get Cortana to recognise me without shouting. I think the mike is somewhere behind the speaker grill as I can get better results talking to that end of the device than the other. Its not brilliant – but it is there. Maybe as Cortana isnt available in China no-one panicked to get a mike working well?
A microphone appears in the device manager and in the sound section of the control manager. I only get levels if I really raise the settings. I wonder if they forgot to put the mic hole in the metal chassis. Nothing would surprise me. The production quality is very poor. This tablet is turning into an expensive lemon.