<p>An audio signal decoding method includes: obtaining the low band signal component of an audio signal when the audio signal corresponding to the received encoding code stream is converted from a first band width to a second band width wherein the first band width is wider than the second band width (S303), extending out the high band information from the low band signal component (S304), making a graduated out process of time variable for the extended high band information to obtain the processed high band signal component (S305), and synthesizing the processed high band signal component with the obtained low band signal component (S306).</p>
