Most stutterers speak too quietly and too fast. They can't wait to get it over with and they think if they speak quietly no one will hear them stutter. If you speak in a crazy voice by yourself as an exercise the chances are you won't stutter because your brain doesn't recognize that as your voice. Your brain only requires YOU to stutter. It doesn't recognize that crazy voice as being you so it allows you not to stutter. It's a crazy thing, fighting with your own mind.