Configure the GamePad Sound Output
1.
Scroll to System Settings and press the A button.
2.
Scroll to Wii U GamePad and press the A button.
3.
Scroll to GamePad Sound Output Type and press the A button.
4.
Scroll to the desired option (e.g. Surround) and press the A button.
You can sample each Sound Output Type by scrolling to Sample and pressing the A button.
5.
Scroll to OK and press the A button.