Anyone knows where are the four Moto x 2014 microphones located?

[Buscador]

I am just curios and have not been able to find any schematics drawings or pics with this info. I am assuming that one microphone is located by the speakerphone, another one is behind the phone near the micro usb connector, the other one between the camera and the headphone connector, where is the other 4th microphone?