It says in the Baal HaTanya's Hilchos Talmud Torah that one fulfills his obligation to learn Torah only if he says the words. Moreover, a Chavrusa fulfills his obligation only because Shomeya Keoneh.
Most Poskim do not consider a person listening to a tape as Shomeya Keoneh. So does one fulfill Mitzvas Talmud Torah by listening to a shiur on a tape?
