A device for reducing quantization noise in a sound signal synthesized from a decoded CELP time-domain excitation ( e(n)), the device being characterized in that it comprises: a first converter for converting the decoded CELP time-domain excitation ( e(n)) into a frequency-domain excitation ( f e (k)); a mask builder responsive to the frequency-domain excitation ( f e (k)) for producing a weighting mask ( G m), the mask builder comprising: a spectral energy normalizer for normalizing an energy of the frequency-domain excitation ( f e (k)) such that tones have a value above 1.0 and valleys a value under 1.0 using the following relation: E n k = E BIN k max E BIN + X where k = 0,...,L -1, L represents a length of a frequency transform used for converting the decoded CELP time-domain excitation ( e(n)) into the frequency-domain excitation ( f e (k)), E BIN ( k) represents an energy of a frequency bin (k) of the spectrum of the frequency-domain excitation ( f e (k)), max( E BIN) represents a maximum frequency bin energy, E n (k) represents a normalized energy spectrum, and X represents an offset used to normalize the energy of the frequency-domain excitation ( f e (k)) between X and (1+ X); means for processing the normalized energy spectrum ( E n (k)) of the frequency-domain excitation ( f e (k)) through a power function to obtain a scaled energy spectrum; means for limiting the scaled energy spectrum to a maximum limit; an energy averager for smoothing the scaled energy spectrum along the frequency axis from low to high frequencies using an averaging filter; and an energy smoother for processing the frequency spectrum from the energy averager along the time domain axis to smooth the bin energy values from frame to frame and produce a time-averaged amplification/attenuation weighting mask; and wherein the device further comprises a modifier for modifying the frequency-domain excitation ( f e (k)) to increase spectral dynamics by application of the weighting mask ( G m) to the frequency-domain excitation ( f e (k)); and a second converter for converting the modified frequency-domain excitation ( f' e (k)) into a modified CELP time-domain excitation ( e' td). a first converter for converting the decoded CELP time-domain excitation ( e(n)) into a frequency-domain excitation ( f e (k)); a mask builder responsive to the frequency-domain excitation ( f e (k)) for producing a weighting mask ( G m), the mask builder comprising: a spectral energy normalizer for normalizing an energy of the frequency-domain excitation ( f e (k)) such that tones have a value above 1.0 and valleys a value under 1.0 using the following relation: E n k = E BIN k max E BIN + X where k = 0,...,L -1, L represents a length of a frequency transform used for converting the decoded CELP time-domain excitation ( e(n)) into the frequency-domain excitation ( f e (k)), E BIN ( k) represents an energy of a frequency bin (k) of the spectrum of the frequency-domain excitation ( f e (k)), max( E BIN) represents a maximum frequency bin energy, E n (k) represents a normalized energy spectrum, and X represents an offset used to normalize the energy of the frequency-domain excitation ( f e (k)) between X and (1+ X); means for processing the normalized energy spectrum ( E n (k)) of the frequency-domain excitation ( f e (k)) through a power function to obtain a scaled energy spectrum; means for limiting the scaled energy spectrum to a maximum limit; an energy averager for smoothing the scaled energy spectrum along the frequency axis from low to high frequencies using an averaging filter; and an energy smoother for processing the frequency spectrum from the energy averager along the time domain axis to smooth the bin energy values from frame to frame and produce a time-averaged amplification/attenuation weighting mask; and wherein the device further comprises a spectral energy normalizer for normalizing an energy of the frequency-domain excitation ( f e (k)) such that tones have a value above 1.0 and valleys a value under 1.0 using the following relation: E n k = E BIN k max E BIN + X where k = 0,...,L -1, L represents a length of a frequency transform used for converting the decoded CELP time-domain excitation ( e(n)) into the frequency-domain excitation ( f e (k)), E BIN ( k) represents an energy of a frequency bin (k) of the spectrum of the frequency-domain excitation ( f e (k)), max( E BIN) represents a maximum frequency bin energy, E n (k) represents a normalized energy spectrum, and X represents an offset used to normalize the energy of the frequency-domain excitation ( f e (k)) between X and (1+ X); means for processing the normalized energy spectrum ( E n (k)) of the frequency-domain excitation ( f e (k)) through a power function to obtain a scaled energy spectrum; means for limiting the scaled energy spectrum to a maximum limit; an energy averager for smoothing the scaled energy spectrum along the frequency axis from low to high frequencies using an averaging filter; and an energy smoother for processing the frequency spectrum from the energy averager along the time domain axis to smooth the bin energy values from frame to frame and produce a time-averaged amplification/attenuation weighting mask; and wherein the device further comprises a modifier for modifying the frequency-domain excitation ( f e (k)) to increase spectral dynamics by application of the weighting mask ( G m) to the frequency-domain excitation ( f e (k)); and a second converter for converting the modified frequency-domain excitation ( f' e (k)) into a modified CELP time-domain excitation ( e' td).