A device for modifying, during decoding of a sound signal, a synthesis of a time-domain excitation decoded by a time-domain decoder, comprising: a classifier (104, 105, 106) configured to classify the synthesis of the decoded time-domain excitation into one of a number of categories; a first converter (107, 201) configured to convert the decoded time-domain excitation into a frequency-domain excitation; a modifier (107, 203, 204, 205, 206, 207, 208, 209,210) configured to modify the frequency-domain excitation depending on the category in which the synthesis of the decoded time-domain excitation is classified by the classifier (104, 105, 106); a second converter (107, 202) configured to convert the modified frequency-domain excitation into a modified time-domain excitation; a synthesis filter configured to be supplied with the modified time-domain excitation to produce a modified synthesis of the decoded time-domain excitation; wherein the modifier (107, 203, 204, 205, 206, 207, 208, 209, 210) comprises: a calculator configured to calculate a cut-off frequency where a time-domain excitation contribution stops to be used, wherein the cut-off frequency has a minimum value of 1.2 kHz; a zeroer configured to zero the frequency-domain excitation above the cut-off frequency; a normalizer of the frequency-domain excitation below the cut-off frequency; a random noise generator configured to generate a random noise; and an adder configured to add the random noise to the frequency-domain excitation zeroed above the cut-off frequency and normalized below said cut-off frequency. a classifier (104, 105, 106) configured to classify the synthesis of the decoded time-domain excitation into one of a number of categories; a first converter (107, 201) configured to convert the decoded time-domain excitation into a frequency-domain excitation; a modifier (107, 203, 204, 205, 206, 207, 208, 209,210) configured to modify the frequency-domain excitation depending on the category in which the synthesis of the decoded time-domain excitation is classified by the classifier (104, 105, 106); a second converter (107, 202) configured to convert the modified frequency-domain excitation into a modified time-domain excitation; a synthesis filter configured to be supplied with the modified time-domain excitation to produce a modified synthesis of the decoded time-domain excitation; wherein the modifier (107, 203, 204, 205, 206, 207, 208, 209, 210) comprises: a calculator configured to calculate a cut-off frequency where a time-domain excitation contribution stops to be used, wherein the cut-off frequency has a minimum value of 1.2 kHz; a zeroer configured to zero the frequency-domain excitation above the cut-off frequency; a normalizer of the frequency-domain excitation below the cut-off frequency; a random noise generator configured to generate a random noise; and an adder configured to add the random noise to the frequency-domain excitation zeroed above the cut-off frequency and normalized below said cut-off frequency. a calculator configured to calculate a cut-off frequency where a time-domain excitation contribution stops to be used, wherein the cut-off frequency has a minimum value of 1.2 kHz; a zeroer configured to zero the frequency-domain excitation above the cut-off frequency; a normalizer of the frequency-domain excitation below the cut-off frequency; a random noise generator configured to generate a random noise; and an adder configured to add the random noise to the frequency-domain excitation zeroed above the cut-off frequency and normalized below said cut-off frequency.