svoid dm_lowerVoiceVolume_speak(O... _) {
  Float vol = dm_getVoiceOutputVolume();
  if (vol == null) ret;
  optPar float factor = 0.80f;
  print("Volume: " + vol + ", factor: " + factor);
  dm_setVoiceOutputVolume(vol *= factor);
  dm_sayInEnglish("New volume: " + toIntPercent(vol) + "%");
}