13. The system of claim 12 , further comprising an energy level classifier to classify each of the plurality of frames according to respective energy levels based on predetermined criteria, wherein the change detector detects a segment in which respective energies of each frame are changed based on the classified energy level.
13. The system of claim 12 , further comprising an energy level classifier to classify each of the plurality of frames according to respective energy levels based on predetermined criteria, wherein the change detector detects a segment in which respective energies of each frame are changed based on the classified energy level. 14. The system of claim 13 , further comprising: an energy calculator to calculate energies of each frame; an energy level updater to update the predetermined criteria according to the energies of each signal; wherein the energy level classifier classifies frames into three levels including high, medium, and low levels.