Including the category of environmental noise when processing speech signals

A method of identifying a noise environment in which a noisy input signal was generated, the method comprising:

• identifying frames of the noisy input signal;
• generating a noisy input feature vector for the signal in each frame;
• for each frame, making a separate identification of a noise environment in which the noisy input feature vector for the current frame was generated based on the noisy input feature vector;
• dividing a feature vector space associated with the environment into sub-spaces by sequentially dividing the feature vector space using a set of boundary conditions;
• comparing the noisy input feature vectors with at least one of the boundary conditions to identify a closest codeword of a set of codewords associated with the environment;
• and
• selecting a correction vector associated with the closest codeword to apply to the noisy input feature vector to produce a clean feature vector.