1. A device implemented in a CELP coder for quantizing a gain of a fixed contribution of an excitation in a frame, including sub-frames, of a coded sound signal, comprising: an input for a parameter representative of a classification of the frame; an estimator of the gain of the fixed contribution of the excitation in a sub-frame of said frame, wherein the estimator is supplied with the parameter representative of the classification of the frame; and a predictive quantizer of the gain of the fixed contribution of the excitation, in the sub-frame, using the estimated gain; wherein the predictive quantizer determines a correction factor for the estimated gain as a quantization of the gain of the fixed contribution of the excitation, and the estimated gain multiplied by the correction factor gives the quantized gain of the fixed contribution of the excitation; wherein the estimator comprises, for a first sub-frame of the frame: (a) a calculator of a linear estimation of the gain of the fixed contribution of the excitation in logarithmic domain in response to the parameter representative of the classification of the frame; (b) a subtractor of an energy of a filtered innovation codevector from a fixed codebook in logarithmic domain from the linear gain estimation from the calculator, the subtractor producing a gain in logarithmic domain; (c) a converter of the gain in logarithmic domain from the subtractor to linear domain to produce the estimated gain; and (d) a multiplier of the estimated gain by the correction factor to produce the quantized gain of the fixed contribution of the excitation; and wherein each of the estimator, predictive quantizer, calculator, subtractor, converter, and multiplier is configured to be processed by one or more processors, wherein the one or more processors is coupled to a memory.