A video explaining what is needed for the sound effects and some different suggestions for how to obtain them.
For more tutorials and information:
http://gbatemp.net/threads/custom-3ds...
2021/09/30
Thanks to a surely good-hearted samaritan I have seen the light and will amend this video via this description and make it as short and concise as possible.
tl;dw: Stop using usagi, it's dead. Use kame-editor, it doesn't need bullshit like ctr32_wav_converter.