What to do:
1. From the Wii U Menu, tap "System Settings."
2. Using the Left Stick scroll to the "Wii U GamePad" icon and press the A Button.
3. Select "Microphone Test."
4. When the microphone meter appears on the screen, speak into the microphone on the Wii U GamePad. The meter will fill from yellow to orange to indicate the volume it is picking up.
5. When you are finished, press the B Button.