I've heard the DLC allows WAV format playback, but I don't own it myself so I can't confirm that. It isn't possible to directly export/import any kind of file between SmileBASIC and a PC. SmileBASIC is very sandboxed within the 3DS system. There are more indirect ways to transfer files, however. Note that these methods aren't endorsed by SmileBoom, but user-made and aren't particularly fast.