12. The pronunciation variation rule extraction method according to claim 11 , further comprising generating a probability rule of pronunciation variation from said pronunciation variation example, wherein said generating said probability rule includes generating said probability rule of said pronunciation variation based on a magnitude of said weight value of said sub word language model upon observation of said pronunciation variation example, such that said pronunciation variation example has a high appearance probability.
11. The pronunciation variation rule extraction method according to claim 8 , wherein said extracting includes: calculating said difference as an editing distance between said recognition result and said base form pronunciation data; and extracting as said difference, a pronunciation variation example including a letter string pair of different portions between said recognition result and said base form pronunciation data and said weight value of said sub word language model received upon acquisition of said recognition result.