11. The HMM learning device according to claim 1 , wherein before performing learning by said additional learning method, the regions of said state transition probability table and said observation probability table stored as said internal mode data are extended, and a state transition probability and an observation probability are set to said extended regions respectively, in the case that the number of said nodes increases.
11. The HMM learning device according to claim 1 , wherein before performing learning by said additional learning method, the regions of said state transition probability table and said observation probability table stored as said internal mode data are extended, and a state transition probability and an observation probability are set to said extended regions respectively, in the case that the number of said nodes increases. 12. The HMM learning device according to claim 11 , wherein based on a state transition probability obtained from said state transition probability table stored as said internal model data obtained based on the past learning, the state transition probability is set to said extended region of said state transition probability table.