svoid convertAllWAVInDirToMP3(File dir) {
  for (File wav : listFilesWithExtension(dir, "wav")) {
    File mp3 = replaceExtension(wav, "wav", "mp3");
    if (mp3.exists())
      print("File exists, skipping: " + mp3);
    else
      wavToMP3_128k(wav, mp3);
  }
}