Speech encoding method and apparatus and and audio decoding method and apparatus

PROBLEM TO BE SOLVED: To provide a speech coding and decoding method for improving tone quality of a decoded voice by bringing a harmonic structure of an encode noise near to the harmonic structure of an input signal. SOLUTION: An error signal 102 showing a difference between an input voice information signal 100 and a synthetic voice information signal 107 corresponding to the input voice information signal is generated, and a pitch weighting extent for the error signal is changed according to a frequency, and a weighting signal 119 is generated, and index information 121 is generated, based on the weighting signal. The index information is extracted from encode voice information, and a decode voice signal is generated, based on the index information, and a pitch emphasizing extent is changed according to the frequency, and pitch emphasizing processing is applied to the decode voice signal.