You can use this feature to verify that the Nintendo DSi's built-in microphone is working properly.
How to test the microphone:
- On the System Settings Menu, go to page 3, then select "MIC TEST."
- Speak into the microphone.
The volume bar will fill up with coloured bars when it picks up sound.
If the volume bar does not fill up, check whether anything is connected to the headset port.
If the volume bar responds, then the microphone is working properly.