Simple.. Which microphones are used on the Lenovo P2 phone.
On a call: The one on the bottom left of the phone edge, down and to the left of the home button.
When on speakerphone: The one at the top edge of the phone.
Voice Recorder (by Splend Apps): The one on the bottom left of the phone edge, down and to the left of the home button.
Recording a video using inbuilt app or Open Camera: The one on the bottom left of the phone edge, down and to the left of the home button and the one at the top edge of the phone. The top microphone is the left audio channel and the bottom left microphone is the right audio channel. (Possibly reversed depending on orientation of the phone I guess).
Modified original picture of phone by Rajat491 – CC BY-SA 4.0, https://en.wikipedia.org/w/index.php?curid=53211368
thecomputerperson 