12. A speech recognition system including at least one processing device, the system comprising: a change detector to detect, using the at least one processing device, energy changes between a plurality of frames distinguishing portions of a signal, each of the plurality of frames having lengths less than a whole time length of the signal; and a determiner to identify speech segments and/or non-speech segments from the plurality of frames based on the detected energy changes between the plurality of frames by assigning a predetermined weight to a segment in which an energy level of a respective frame is changed and when an energy difference exists between two neighboring frames.
16. The system of claim 12 , wherein the determiner repeatedly performs processes of assigning the predetermined weight to a segment in which an energy level of a respective frame is changed and calculating weights for all respective segments in order to identify a segment corresponding to a minimum weight, among the calculated weights, as being a speech segment, wherein the segment corresponding to the minimum weight has a lower energy level than the other speech segments.