Editing effects is likened to creating the sonic world from scratch, while dialogue editing is likened to taking the existing sonic world and fixing it. Dialogue editing is more accurately thought of as "production sound editing", where the editor takes the original sound recorded on the set, and using a variety of techniques, makes the dialogue more understandable, as well as smoother, so the listener doesn't hear the transitions from shot to shot (often the background sounds underneath the words change dramatically from take to take). Among the challenges that effects editors face are creatively adding together various elements to create believable sounds for everything you see on screen, as well as memorizing their sound effects library.