Definition of Problem
¡For level 1~level 2, suppose a sequence of meaningful units can be perceived by  Human Beings from the raw audio data as:
¡                      {                 }
¡   The problem is how to detect the same  sequence  from the raw data automatically.
¡For level 2~level 3, suppose the sequence obtained from low level signal processing is:{                 }
¡    The problem is how to use high level knowledge to correct the error introduced by low level signal processing and get the sequence of
¡                         {                  }