1. A method for performing time and frequency SNR dependent weighting in speech recognition comprising the steps of: for each speech frame t estimating the SNR to get time and frequency SNR information η t,f ; calculating the time and frequency weighting to get γ tf ; performing the back and forth weighted time varying DCT transformation matrix computation MG t M −1 to get T t ; providing the transformation matrix computation T t and the original MFCC feature o t that contains the information about the SNR to a recognizer including the Viterbi decoding; and performing weighted Viterbi recognition b j (o t ).