3. The speech recognition system of claim 1 or 2 , wherein the speech signal is transformed to the varied phoneme sequence by using a first decoding equation, the first decoding equation being represented by following Equation 1, T * = arg ⁢ ⁢ max T ⁢ P ( T ⁢  X ) Equation ⁢ ⁢ 1 wherein X indicates a vector sequence corresponding to the feature parameters of the input speech signal and T represents a phoneme sequence.
4. The speech recognition system of claim 3 , wherein the varied phoneme sequence satisfies a condition that maximizes a multiplication of a prior probability and a conditional probability and is obtained by following Equation 2, Equation 2 being derived from Equation 1 by using Bayes' rule, T * = ⁢ arg ⁢ ⁢ max T ⁢ P ( T ⁢  X ) = ⁢ arg ⁢ ⁢ max T ⁢ P ( X ⁢  T ) ⁢ P ⁡ ( T ) P ⁡ ( X ) ≈ ⁢ arg ⁢ ⁢ max T ⁢ P ( X ⁢  T ) ⁢ P ⁡ ( T ) . Equation ⁢ ⁢ 2