7. A method of normalizing input data of an acoustic model, the method comprising: extracting windows of frame data to be input to the acoustic model from frame data of a speech to be recognized; and normalizing the frame data to be input to the acoustic model in units of the extracted windows, wherein the normalizing of the frame data comprises normalizing frames belonging to a current window in consideration of frames belonging to preceding windows of the current window.
7. A method of normalizing input data of an acoustic model, the method comprising: extracting windows of frame data to be input to the acoustic model from frame data of a speech to be recognized; and normalizing the frame data to be input to the acoustic model in units of the extracted windows, wherein the normalizing of the frame data comprises normalizing frames belonging to a current window in consideration of frames belonging to preceding windows of the current window. 8. The method of claim 7 , wherein the extracting of the windows comprises consecutively extracting the windows in units of a predetermined number of frames of the frame data of the speech to be recognized while the frame data of the speech to be recognized is being input.