1. A method of compensating for additive and convolutive distortions applied to a signal indicative of an utterance, comprising: receiving the signal indicative of an utterance; initializing a noise mean vector and a channel mean vector; calculating a Gaussian dependent compensation matrix and updating Hidden Markov Model (HMM) parameters to account for additive noise from the noise mean vector or convolutive distortion from the channel mean vector; adapting the HMM parameters by: decoding the utterance using the previously calculated HMM parameters; and adjusting the Gaussian dependent compensation matrix and updating the HMM parameters based upon data received during the decoding; and applying the adapted HMM parameters to decode the utterance and provide a transcription of the utterance.