A CELP signal decoding apparatus for decoding coded information constructed in a plurality of layers, the apparatus comprising: a decoding section adapted to decode the coded information of each layer, and further adapted to generate a plurality of decoded signals; a gain adjustment section adapted to adjust a gain of each of the plurality of decoded signals; and an addition section adapted to add up the plurality of gain adjusted decoded signals, and to generate an addition signal; characterized by a decoding operation control section adapted to control the gain adjustment section by separately setting one of a first, a second and a third gain adjustment state for each of the plurality of decoded signals of the respective layers, thereby adjusting the gains of the plurality of decoded signals; wherein, for each of the plurality of layers: the first or the second or the third gain adjustment state is set for processing the decoded signal of the respective layer of a current frame, wherein the set gain adjustment state depends on whether, for the respective layer, a previous frame and a subsequent frame comprises coded information or not, such that the magnitude of the decoded signal of the respective layer of the previous frame is faded into the magnitude of the decoded signal of the respective layer of the subsequent frame, wherein in the first gain adjustment state, the gain adjustment section sets the gain of the input decoded signal such that the output gain adjusted decoded signal is increased from zero to a magnitude of the input decoded signal; and wherein in the second gain adjustment state, the gain adjustment section sets the gain of the input decoded signal such that the output gain adjusted decoded signal is decreased from a magnitude of the input decoded signal to zero; and wherein in the third gain adjustment state, the gain adjustment section maintains a magnitude of the input decoded signal. a decoding section adapted to decode the coded information of each layer, and further adapted to generate a plurality of decoded signals; a gain adjustment section adapted to adjust a gain of each of the plurality of decoded signals; and an addition section adapted to add up the plurality of gain adjusted decoded signals, and to generate an addition signal; characterized by a decoding operation control section adapted to control the gain adjustment section by separately setting one of a first, a second and a third gain adjustment state for each of the plurality of decoded signals of the respective layers, thereby adjusting the gains of the plurality of decoded signals; wherein, for each of the plurality of layers: the first or the second or the third gain adjustment state is set for processing the decoded signal of the respective layer of a current frame, wherein the set gain adjustment state depends on whether, for the respective layer, a previous frame and a subsequent frame comprises coded information or not, such that the magnitude of the decoded signal of the respective layer of the previous frame is faded into the magnitude of the decoded signal of the respective layer of the subsequent frame, wherein in the first gain adjustment state, the gain adjustment section sets the gain of the input decoded signal such that the output gain adjusted decoded signal is increased from zero to a magnitude of the input decoded signal; and wherein in the second gain adjustment state, the gain adjustment section sets the gain of the input decoded signal such that the output gain adjusted decoded signal is decreased from a magnitude of the input decoded signal to zero; and wherein in the third gain adjustment state, the gain adjustment section maintains a magnitude of the input decoded signal. <EOS>