1. A recipient mobile terminal receiving voice frames from an originator mobile terminal, the recipient mobile terminal comprising: a communicating unit configured to receive voice frames from the originator terminal if a call is connected with the originator terminal; a vocoder configured to recognize an encoding rate of the received voice frames, to output the recognized encoding rate of the voice frames, and to decode the voice frames at a decoding rate equal to the recognized encoding rate; an amplifier configured to amplify the voice frames decoded by the vocoder and then to output the amplified voice frames to a speaker of the recipient mobile terminal; and a control unit configured to: recognize the encoding rate of the voice frames via the vocoder before the voice frames are decoded by the vocoder, search for at least one voice frame that is equal to a preset encoding rate in the recognized encoding rate of the voice frames before the voice frames are decoded by the vocoder, delete the searched at least one voice frame of the voice frames before the voice frames are decoded by the vocoder, and control the vocoder to decode the voice frames after the searched at least one voice frame is deleted.