10. The method of claim 7 , the normalizing of the frame data comprises normalizing the frames belonging to the current window in consideration of the frames belonging to the preceding windows and frames of training data in response to a total number of the frames belonging to the current window and of the frames belonging to the preceding windows being insufficient for speech recognition.
11. The method of claim 10 , wherein the normalizing of the frame data comprises: comparing the total number of the frames belonging to the current window and the preceding windows with a reference value in response to the current window being extracted; and acquiring a number of frames corresponding to a difference between the total number of the frames and the reference value from the training data in response to the total number of the frames being less than the reference value.