Great article ... it articulates the four categories of tasks very well. I've found podcasts and audio books are the same as music with lyrics - I can listen to them during the Trivial and Physical Exercise categories but not during the Requires Concentration and Reading categories.

Curiously, if I'm concentrating or reading, I don't hear the content at all (though it can distract me). Friends report that they hear the podcast but don't remember the task.