DraStic

How to use the microphone?

First, could you try this ROM: micrecord.nds It will let you record and playback something to see if the microphone is working. You can check that it works at all, that the pitch sounds correct, and that it doesn't sound too quiet.

If this works, you can then try using headphones or turning down the game's volume. Some have reported that this helps.

It's possible that on a real DS the microphone is better isolated from the speakers so it picks up less of the game audio than it would on a phone, where the recording wasn't really designed to be used while the device plays music.