3. The acoustic model learning device according to claim 2 , wherein each of the learning units estimates a parameter by using an iterative method based on any one of a maximum likelihood estimation method, a maximum a posteriori estimation method, and a Bayes estimation method.
3. The acoustic model learning device according to claim 2 , wherein each of the learning units estimates a parameter by using an iterative method based on any one of a maximum likelihood estimation method, a maximum a posteriori estimation method, and a Bayes estimation method. 4. The acoustic model learning device according to claim 3 , wherein the environment-independent acoustic model is a Gaussian mixture model or a hidden Markov model.