A secondary microphone is an extra microphone that is used to record sound in addition to the main microphone. It helps to capture clear and accurate audio from different angles or distances. Full definition
Moving up, the top is bare except for the lonely secondary microphone. (pokde.net)
The top edge of the Galaxy Note is home to a standard 3.5 - millimeter audio jack as well as a small secondary microphone for noise cancellation. (bgr.com)
On the top there is another SIM tray along with secondary microphone. (gogi.in)